ECOLOGIGAL TNVESTFGATIONS 0N TFiE CEREAL LEAF BEETLE. OULENTA AHELAWSPUS (L) AM) 1! i...IHI PRINCIPAL mam PARASITE. if? :5.-'f.f.'§75f§9}f:7 ‘ : TEFRASTICHUS jULS (WALKER) Iii}: xiii—ET: DiSSDTTdUOF for the Degree of Ph D. ' ' MECHIPA‘T STAT-E UNIVERSITY ' STUBRTHARGRAFT GAGE 3 1293 10350 “’07 LIBRARY Michigan Sum University This is to certify that the thesis entitled ECOLOGICAL INVESTIGATIONS ON THE CEREAL LEAF BEETLE, OULEMA MELANOPUS (L.), AND THE PRINCIPAL LARVAL PARASITE TETRASTICHUS JULIS (WALKER) presented by Stuart Hargraft Gage has been accepted towards fulfillment of the requirements for PhD degree in Entomology ’ ‘ / ,r I ‘7 14.6 a u fiyL Lift/1&4) Major professo} Date June 7, 1974 ’39 {3800K 3mm? ‘ yr L_:8'_‘."'3\, (I vf ‘r: ‘ ”I ‘PR'hhr 7" li""|""_¢v , l: 5 . - I ABSTRACT ECOLOGICAL INVESTIGATIONS ON THE CEREAL LEAF BEETLE, OULEMA MELANOPUS (L.), AND THE PRINCIPAL LARVAL PARASITE, TETRASTICHUS JULIS (WALKER) By Stuart Hargraft Gage Tetrastichus iulis (Walker) is one of four parasites of the cereal leaf beetle, Oulema melanopus CL.) introduced and established at the Kellogg Biological Station, Hickory Corners, Michigan. This study ex- amines some of the salient biological characteristics of I, 12115, in- cluding rates of development, emergence, diapause, and its interaction with populations of g, melanoEus and other parasites. Quantitative estimates of parasite and host populations were made using a number of methods, including population counts of the host and parasites on winter wheat and spring oat foliage, and a sweep survey to obtain regional estimates of hosts and parasites at Gull Lake. Parasitism of the total population of Q, melanopus by I, 1211: increased from 0.7% in 1969 to 40% in 1973 in the section where I, jgli§_ was originally released. I, igli§_dispersed to other areas at Gull Lake and build—up lagged slightly behind the original release site. Populations of Q, melanopus decreased from 198 larvae per ft2 per season in 1969 to 4 per ft2 per season in 1973. Part of the decline in Q, melangpus density is due to parasitism by I: igli§_and part to high mortality in 1971, when high soil temperatures and low rainfall during (if {53) Stuart Hargraft Gage lffifi and after pupation killed 49 and 58% of Q, melanopus and I, julis in the pupal cell. I, iEII§_populations are vulnerable to some commonly practiced farming methods, such as plowing stubble after harvest and prior to adult I, iEII§_emergence in the spring. Management procedures are suggested to optimize sampling and survival of I, igII§_on a regional basis. It was not possible to show that I, igII§_populations were re- sponsrble fer the general decrease in 9, melanopus density since 1969. However, by 1973, I, igIIg was contributing to more than 80% of Q, melanopus mortality in the soil. I, lEgI§_is an important parasite of _0_. melangus, and a regional management scheme for regulation of Q, melanopus populations must include the possibility of natural control by I, julis. ECOLOGICAL INVESTIGATIONS ON THE CEREAL LEAF BEETLE, OULEMA MELANOPUS (L.), AND THE PRINCIPAL LARVAL PARASITE, TETRASTICHUS JULIS (WALKER) BY Stuart Hargraft Gage A DISSERTATION Submitted to Michigan State University in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY Department of Entomology 1974 To Patricia and Jennifer ACKNOWLEDGEMENTS I would like to thank James E. Bath, Chairman, Department of Entomology, Herman E. Koenig, Chairman, Department of Electrical Engineering and Systems Science, and the U.S.D.A. fer providing en- couragement and financial assistance during this study. To Fred W. Stehr, R. Lal Tummala, Don J. Hall and Jim B. Bath 1 would like to extend my appreciation for serving on my guidance com- mittee and reviewing this manuscript. Several individuals helped with field work and data processing and I thank them all. I would especially like to thank Mike Connor who did excellent field work for several seasons, Mary Citadino, who served as my number one helper during the final stages of putting the manuscript together and Lucy Wells for typing the final draft. Above all, I sincerely appreciate the guidance given me through- out this study and many of my other endeavours by Dean L. Haynes who was my major professor. I am very proud to have been one of Dean's students. iii TABLE OF CONTENTS LIST OF TABLES . LIST OF FIGURES INTRODUCTION . LITERATURE REVIEW MATERIALS AND METHODS Quantitative sampling methods Sampling time and logistics Gull Lake management plan RESULTS Development of I, julis under laboratory conditions Daily emergence of T. julis and summer CLB adults Emergence trap efficiency . . . . . . . Flight behavior of‘I_. Iulis Attack behavior of T. lulis . . . . . Laboratory assessmefit of T. julis fecundity Incidence of diapause in T} julis . Mortality of I_. julis and_ CLB in —the soil Effects of manipulating the soil on I_. julis . CLB larval population trends at Gull Lake (1967 - 1973) . . . . . . . . Distribution of I, julis at Gull Lake Impact of T. julis on the CLB population . Interaction ofI julis with A. flavipes . I 1_I( DISCUSSION . Some general management considerations . Regional management of the CLB using I. julis as the principal biological component Expansion of data collected at Gull Lake to a regional basis for interpretation of CLB and I, julis population interaction and management . iv Page vi xi 15 15 22 25 30 3O 36 44 48 55 58 59 68 70 75 90 102 128 133 133 137 149 Page SUMMARY AND CONCLUS IONS . . . . . . , . . . . . . . . . . . . . . 15 8 LITERATURE CITED . . . . . . . . . . . . . . . . . . . . . . . . 161 APPENDICES . . . . . . . . . . . . . . . . . . . . . . . . . . . . 167 I ‘il‘ l . I. l I I A A I II A 1" 1 IT ill III. III l Table 10. 11. LIST OF TABLES Status in Europe of three larval parasites of Q, melanopus based on 44 collection sites . A summary of some biological aspects of parasites imported from Europe as noted by Andersen and Paschke (1968) on the egg parasite, and Dysart et al. on the larval parasites . . . . . . . . . . Quantitative methods used to sample pOpulations of the cereal leaf beetle and I, julis . Field sampling activities in sections 5, 8, and 9 at Gull Lake Development of I, julis at constant and oscillating temperatures Development of T. ulis at 70° F from time of removal from storage (42 F until adult emergence Regression equations relating the number of degree— days accumulated above a threshold of 48° F (° D4 ) in aid (° D ) to °D48 accumulated 2 inches in the $011 (° D S) at Gull Lake Probit equations, X2 values, and degrees of freedom for adult I. julis emergence curves shown in Figure 8. _Ep is probit emergence and °D48 is accumulated heat above 48° F (air temperature) Degree-day values for different percent emergence of adult I, julis during the first and second generations (1971-1973) . Number of female and male T. julis trapped in emergence traps containing foliage cut at different heights . . . . . . . . . . . . . . . . . . . . . Total number of T. julis caught in rotary flight traps in different crops at different heights during the spring and summer generations, 1973 vi Page 16 26 31 35 38 42 45 47 SO Table 12. l3. 14. 15. 16. 17. 18. 19a. 19b. 20. Comparison of the number of non- -diapausing and diapausing T. julis in cereal leaf beetle pupal cells collected at different dates . . . Comparison of the percent frequency of I, julis individuals per cereal leaf beetle pupal cell from laboratory reared larvae (non-diapausing) with cells collected from soil (diapausing) . Mean length and width of female and male I, julis which emerged from cells containing different numbers of parasites (X t SE (n)) Total rain (inches) and 0048 per month (April-July) for the years population density estimated were made fOr the cereal leaf beetle at Gull Lake . Percent mortality of the cereal leaf beetle and julis determined from examination of pupal cells collected from oat fields at Gull Lake . . . . . . Mean number of T. julis adults per yd2 trapped from different oat stubble treatment, 1971-1973 (X— SE) 0 o o o o o o o o o o o o o o o o o o o o o The initial, peak, and last cereal leaf beetle egg and larval populations in spring oats with respect to °D 48000000000000.0000... Population density in spring oats and winter wheat per ft2 per season of cereal leaf beetle eggs and larvae (total area under seasonal population curve - developmental time), trend index of larval density (NL(t+1)/NLét})» and the ratio of eggs per ft2 to larvae per in the same section in different years at Gull Lake . . . . . . . . . . . . . . . . . . . Population density in spring oats and winter wheat per ft2 per season of cereal leaf beetle eggs and larvae (total area under seasonal population curve % developmental time) and the ratio of eggs per ft2 to larvae per ft2 in different sections and years at Gull Lake . . . . . . . . . . . . . . . The relationship between peak egg and peak larval density per ft2 and corresponding total incidence of eggs and larvae per season in spring oats and winter wheat at Gull Lake . . . . . . . . . . vii Page 63 64 67 69 72 74 79 82 87 89 . IA .Ai i A A i (15'. AI 1 all! ll i Ilil lull i I l . Ii i i A i i i. JTI Table 21. 22. 23. 24. 25. 26 27. 28. 29. 30. 31a. 31b. Mean number of spring and summer generation I, julis adults and cereal leaf beetle summer adults emerging per yd2 from several oat fields sampled in the three sections at Gull Lake. These estimates show the highest densities from the oat fields sampled in each section . . . . . . . . . . . . . . . . The effect of crap and crop age (early or late) on production of I, julis (summer generation) and cereal leaf beetle adults . Mean number of T. julis trapped from stubble at Gull Lake in different sections during spring emergence, 1973 . . . . . . . . . . Mean number of I, julis and cereal leaf beetle adults trapped at Gull Lake in different sections during the summer generation, 1973 Differences in cereal leaf beetle production within a field depending on elevation differences, 1970 Differences in crop age on the number of cereal leaf beetle and parasites produced in 1970 Comparison of two methods used to remove cereal leaf beetle pupal cells from the soil in 1971 Differences in mean number and mortality of cereal leaf beetle and T. julis during drought conditions when 1/2 ydz soil samples were taken inside and adjacent to emergence traps in 1971 . Mean number per l/2 yd2 of cereal leaf beetle cells and mean number of cells containing diapausing T. julis larvae in samples taken from representative fields of normally planted oats in different years in each of three sections at Gull Lake Density of cereal leaf beetle cells and density of parasitized cells per 1/2 yd2 sampled in July, 1973, in three sections at Gull Lake . . Mean maximum number of I, julis adults per ft2 in three different ages of cats and wheat during the first and second generations in 1972 (n = 20) Mean maximum number of I. julis adults per ft2 in two different ages of oats and wheat during first and second generations in 1973 (n = 20) viii Page 91 93 94 95 97 97 97 100 101 103 111 111 Table 32a. 32b. 33. 34. 35. 36. 37a. 37b. 38. Number of cereal leaf beetle larvae per adult .julis based on peak T. julis density per ft2 in 1972 in three ages of oats and wheat in section 9 at Gull Lake Number of cereal leaf beetle larvae per adult __ julis based on peak I_. julis density per ft2 in 1973 in two ages of oats and wheat in section 9 at Gull Lake Population density in spring oats per ft2 per season of cereal leaf beetle larvae and larvae parasitized by I, julis (total area under seasonal pOpulation curves - developmental time) and effective parasitism by T. julis determined from weekly pOpulation samples in three sections at Gull Lake . . Population density in different ages of winter wheat and spring oats per ft2 per season of cereal leaf beetle larvae and larvae parasitized by I_. julis (total area under seasonal population curves % deve10pmental time) and effective parasitism by I, julis determined from weekly population samples in section 9 at Gull Lake . Percent parasitism on different dates determined from collection of 25 late instar larvae from early and late oat fields in three sections at Gull Lake Density in different ages of spring oats and winter wheat per sweep per season of cereal leaf beetle larvae and larvae parasitized by T. julis (total area under seasonal curve — developmental time) and effective parasitism by T. julis in three different sections at Gull Lake in 1972 . . . . . Density in different ages of spring oats per sweep per season of cereal leaf beetle larvae and larvae parasitized by I, julis (total area under seasonal curve % developmental time) and effective parasitism by I, julis in different sections at Gull Lake in 1973 Density in different ages of winter wheat per sweep per season of cereal leaf beetle larvae and larvae parasitized by T. julis (total area under seasonal curve - develOpmental time) and effective parasitism by I_. julis in different sections at Gull Lake in 1973 Ratio of cereal leaf beetle cells parasitized by T. Julis to the total number of cereal leaf beetle pupal cells per 1/2 ydz, determined from soil samples taken in early planted oat fields ix Page 113 113 114 115 117 121 122 123 125 Table 39a. 39b. 40a. 40b. 41. 42. 43. 44. Classification of cereal leaf beetle pupal mortality due to undetermined death and parasitism between 1970-1973 from oat fields in section 9 at Gull Lake. Density estimates are fer 1/2 yd2 samples . Percent mortality % 100 due to each of the components from density estimates given in Table 39a . Classification of cereal leaf beetle pupal mortality due to undetermined death and parasitism in 1973 from oat fields in three sections at Gull Lake. Density estimates are from 14 1/2 yd2 samples per field . Percent mortality e 100 due to each of the components from density estimates given in Table 40a . Total number of cereal leaf beetle larvae collected by U.S.D.A. personnel at the Gull Lake field insectary and estimates of total parasitized cereal leaf beetle larvae by I, julis . Symbolic reference table for decision making maps of first generation I, julis emergence (Figures 32 and 33) Total rainfall during May and June, °D during June at Gull Lake, and average oat yield (bu./acre) in Kalamazoo Co. from 1967-1972 . . . . . . A comparison of cereal leaf beetle larval population densities per ft2 at Gull Lake and in Jackson County Page 127 127 129 130 139 141 153 156 llT ALIA I‘ll .lll‘.[/ii\(i»il\[.ill.llillll| lllllI‘ll‘li II II. Figure 9a. 9b. 10. LIST OF FIGURES Page Procedures for extraction of cereal leaf beetle pupal cells from soil samples . . . . . . . . . . . . . . . . . 20 Average occurrence of life stages of the cereal leaf beetle and I, julis at Gull Lake (°D48) . Aerial photograph of the Gull Lake Biological Station and surrounding area indicating sections 5, 8, and 9 where detailed cereal leaf beetle research was conducted . . . . . . . . . . . . . . . . . . . . . . . . . 27 24 Field maps of sections 5, 8, and 9 at Gull Lake indicating crop planting configurations used in management plans . . . . . . . . . . . . . . . . . . . . . 29 Percent develOpment per day of I, julis post-diapause larvae at different temperatures . . . . . . . 32 Developmental stages of I, julis from diapausing larvae in cereal leaf beetle pupal cell (a) to an emerged adult (1) . . . . . . . . . . . . . . . . . . . . . 34 Average weekly soil temperatures at two inches in oat stubble at Gull Lake (a) and the relationship between air 01348 and $011 01348 (b) . . . . . . . . . . . 37 Cumulative percent emergence of I, julis adults trapped daily from different treatments. The solid lines were fitted using probits. The dotted lines were sight fitted through cumulative percent occurrence of cereal leaf beetle larvae . . . . . . . . . . 41 Cumulative percent emergence of second generation of I, julis adults and summer cereal leaf beetle adults in 1971 and 1972 . . . . . . . . . . . . . . . . . . 41a Emergence of I, julis adults from early (0A) and late ((8) planted oats in 1972 . . . . . . . . . . . . . . 413 Average cumulative percent emergence of I, julis adults during the first and second generations . . . . . . 46 xi iii Tl.li iii Ali idli.l|l(|l.lll\[i\(l.vi I iilllIA-Illli I l i ii i Figure Page 11. The relationship between rotary flight trap net height and percent of total number of adult I, julis caught . . . . . . . . . . . . . . . . . . . . . . 49 12. Comparison of T. julis adults caught in emergence traps in oat stubble and in a rotary flight trap two feet above oat stubble . . . . . . . . . . . . . . . $1 13. The relationship between mean temperature during the trapping period and number of T. julis adults caught in a rotary flight trap four feet above early planted spring oats . . . . . . . . . . . . . . . . . 53 14. A perspective view showing the influence of trap height (2) on the number of adult T. julis caught above oat stubble (y) during the first generation (x). Figure (b) shows a similar perspective of adults caught during the first and second generations above wheat and oats . . . . . . . . . . . . . . . . . . . S4 15. A schematic representation of the principal components of attack by I, julis females . . . . . . . . . . . . . . . 57 16. The relationship between days and eggs laid per I, 'ulis female (a), cumulative eggs per female (b), and emale survival (c) . . . . . . . . . . . . . . . . . . 6O 17. Percent of I, julis in diapause throughout the season . . . 62 18. The relationship between the number of I, julis per cereal leaf beetle pupal cell and adult I, julis body length . . . . . . . . . . . . . . . . . . . . . . . . 66 19. Maximum daily air temperature during June and early July 1971 (x) compared to the average daily maximum (1967-1973) . . . . . . . . . . . . . . . . . . . . . . . . 71 20a. Cereal leaf beetle egg and total larval densities in winter wheat and spring oats, 1967-1969 . . . . . . . . 77 20b. Cereal leaf beetle egg and total larval densities in winter wheat and spring oats 1970-1973 . . . . . . . . . 78 21. Cereal leaf beetle larval trend index in winter wheat and spring oats . . . . . . . . . . . . . . . . . . . 84 22. Ratio of cereal leaf beetle larval incidence to egg incidence in winter wheat and spring oats . . . . . . . 85 23. Phase plot of cereal leaf beetle total egg and larval density per ft2 in spring oats, 1967-1973 . . . . . 86 xii Figure Page 24. The relationship2 between mean number of pupal cells per 1/2 yd2 and the standard error of the mean . . . . . . . . . . . . . . . . . . . . . . . . . . . 99 25. Total incidence of cereal leaf beetle eggs and larvae in winter wheat (a) and spring oats (b) . . . . . . 105 26. Total cereal leaf beetle larvae per ft2 in three ages of wheat and oats in 1972 with corresponding percent parasitism by T. julis. Hatched areas indicate parasitized larvae per ft2 . . . . . . . . . . . . 107 27. Mean daily I. julis adult density per ft2 in winter wheat and spring oats, and mean occurrence of CLB larvae . . . . . . . . . . . . . . . . . . . . . . . . . . 110 28. The relationship between the number of cereal leaf beetle larvae per sweep and number per ft2 . . . . . . . . 119 29. The relationship between cereal leaf beetle egg density per ft2 and percent parasitism by A, flavipes. The hatched area is number of parasitized eggs per ft2 . . . . . . . . . . . . . . . . . 131 30. A schematic representation of the cereal leaf beetle life system indicating mortality parameters and some potential control points . . . . . . . . . . . . . 134 31. General curves of cereal leaf beetle egg and larval densities and corresponding parasitism by A, flavipes and I, julis. Hatched areas show the numbers of individuals parasitized per ft2 . . . . . . . . . . . . . . 136 32. Regional emergence of first generation I, julis adults at five-day intervals in 1971. (See Table 42 for emergence class intervals) . . . . . . . . . . . . . . . . 143 33. Regional emergence of first generation I, julis adults at five-day intervals in 1972. (See Table 42 for emergence class intervals) . . . . . . . . . . . . . . . . 144 34. Illustration of the concept of a biological window. The dark portion (x) indicates the region in Michigan in 1971 where control of adult cereal leaf beetles could be initiated using a short-lives pesticide (malathion) without killing I, julis adults . . . 147 35. Illustration of the concept of a biological window. The dark portion (x) indicates the region in Michigan in 1972 where control of adult cereal leaf beetles could be initiated using a short-lived pesticide (malathion) without killing I, julis adults . . . 148 xiii Figure 36. 37. 38. Page Spring oat and winter wheat acres harvested in 1964 and 1970 . . . . . . . . . . . . . . . . . . . . . . . 150 Average acres of spring oats harvested in three counties surrounding Gull Lake (1967-1972) . . . . . . . . 151 Precipitation during ten-day intervals in June in 1971 and 1972. Darker areas represent increased amounts of rain . . . . . . . . . . . . . . . . . . . . . . 154 xiv INTRODUCTION The cereal leaf beetle, Oulema melanopus (L.), (Coleoptera: Chrysomelidae), is an introduced insect pest of small grains. Haynes (1973) has described aspects which are considered important to the management of cereal leaf beetle populations in North America. One of the important management options available is that of in- troduced parasites, especially since the insect was introduced to North America in the absence of its parasite complex. The cereal leaf beetle is not significantly important in reducing small grain yield in Europe except locally (Miczulski 1971), and it was postulated that regulation may be occurring due to the beetle's parasite complex. Studies were initiated in 1965 to examine the cereal leaf beetle parasite complex in Europe, resulting in shipment of the major para- sites to the 0.8. Four parasites were released and established at Michigan State University's Gull Lake Biological Station, Hickory Corners, Michigan. The order of establishment of each of the parasites was as follows: Anaphes flavipes (Foerster) Hymenoptera, Mymaridae (Maltby g£_gI, 1971); Tetrastichus julis (Walker) Hymenoptera, Eulophidae (Stehr 1970); Diaparsis carinifer (Thomson) HymenOptera, Ichneumonidae (Stehr and Haynes 1971); and, Lemophggous curtus (Townes) Hymenoptera, Ichneumonidae (Stehr g£_§I, 1974). This study is mainly concerned with the biology, build-up, and impact of I, julis on cereal leaf beetle pOpulations at Gull Lake. 2 This parasite species was selected for detailed investigation because its population built up very rapidly during 1970. The rate of build— up indicated I, iEII§_could have a significant impact on cereal leaf beetle populations. It was felt that it might be possible to manage I, 12I1§_through manipulations, such as crop rotation and planting dates, and with these manipulations, develop a system of optimal management of cr0pping practices that would enhance the effectiveness of I, igII§_as a mortality factor operating on cereal leaf beetle populations. Important considerations in the develOpment of a realistic scheme for the management of a pest insect population are the characteristics of the pest population with respect to its distribution, year to year changes in density, and type and amount of damage caused. Fortunately, these aspects have been investigated, or are being investigated at the present time, on a regional basis (Haynes, in preparation) so that new management techniques, when operational, can be tested against historical infermation and provide a measure for the degree of success. Regional surveys are essential to the understanding of the gross behavior of populations in the areas where they are distributed. However, surveys cannot yield the in-depth understanding of the interactions between populations (i.e., host-plant and host-parasite), and synchrony of the populations with the environment which are necessary to develop adequate models for management schemes. This study provides some of the basic elements needed prior to development of integrated programs providing regional control . In 1971 the CLB population dynamics project became one of a class of environmental problems within the context of a grant entitled 3 Ecosystem Design and Management, administered by the College of Engi- neering through the Electrical Engineering and System Science Depart- ment (NSF, GI-20). Developments evolving from this grant, and through the co-operative efforts between members of the CLB population dynamics group and systems scientists, a pest management grant was prepared. Within this grant, five components of pest management were envisioned and are documented to serve as guidelines for the development of a pest management prototype with the initial fecus on the cereal leaf beetle. The five components are: (1) environmental monitoring_which provides the component of climate and weather in relation to biological activity of the insect populations and their interacting components; (2) biological monitoring_which is a regional survey of the biological populations to detect changes in population density and crop configura- tions; (3) biologgcal research which involves studies of populations in detail and provides parameters which can be used in (4) pest ecosystem modeling fer simulation and mathematical experimentation; and, finally, (5) system operation and maintenance which brings all the components together and provides infermation in a usable context for operation and management decisions at regional and/or local levels. Within the context of this pest management framework, this study is principally a contribution to the biological research component but with strong ties to systems modeling. Because of the local nature of the study (Gull Lake), the regional aspects of population changes through time over a broad area are considered by extrapolation using environmental monitoring. Infermation obtained during this study has been utilized to provide parameter estimates and biological insight regarding the role of natural enemies of the cereal leaf beetle within 4 the context of the cereal leaf beetle management system (Haynes 1973, Gage ggth, 1973, Barr £3.21: in preparation, Tummala SENSE: in prepara- tion). A major effort during this investigation has been to make this pest management effort as useful as possible. This framework has provided specific objectives for this research, such as to determine (1) the effect of crop management on larval parasites, (2) the synchro- nization of the parasites with the host and how this synchrony may be manipulated through crop management, (3) the interaction between intro— duced parasites of the cereal leaf beetle, (4) parasite emergence rates to provide on-line estimates of sampling times for regional parasite distribution and dispersal, and (5) measurement of biological components which lead to a quantitative understanding of the interaction between the cereal leaf beetle and I, julis. LITERATURE REVIEW The cereal leaf beetle, hereafter CLB, has become a serious pest of small grains, especially spring grains, in some areas of North America. Population densities sufficient to cause economic loss were first noticed in spring oats in southwestern Michigan in the early 1960's (Castro gI_gI, 1965), and since then the CLB has spread through- out the lower penninsula of Michigan, Illinois, Indiana, Ohio, Penn- sylvania, New York, West Virginia, Kentucky, and eastern Ontario (Haynes 1973). In Europe, the probable source of the Michigan inoculation, the CLB is widely and continuously distributed from the North African coast to central Scandanavia and from the Atlantic coast (including the United Kingdom) east to central Asia (Castro g£_§I, 1965). Economic damage caused by the CLB occurs sporadically in the Balkan states and southwest U.S.S.R. (Hilterhaus 1965; Venturi 1942) but there is little firm evidence why this insect is not a major pest of small grains in Europe. Initial studies on the CLB in the U.S. began with the work of Castro g£_§I, (1965) who investigated the biology of the insect. Re- search has continued on many aspects of the ecology and biology of the CLB and a bibliography of these works has been published (Wellso SE 21' 1970). Additional information on specific components of biology and field ecology is included in works by Helgesen and Haynes (1972) on 6 within-generation mortality, by Ruesink and Haynes (1973) on a sweepnet model for CLB adults, by Ruesink (1971) on adult biology and a systems model of the CLB, and by Gage (1972) on the interaction between the CLB and its host plants. Because of the impact of CLB populations on small grains in Michigan and in other parts of North America, a major attempt by the U.S.D.A. was made in Europe to find parasites of the CLB. The initial surveys were conducted in 1963 and mass collections began in Europe in 1965. Introductions of parasites of the CLB into the U.S. began in 1964 and are still continuing. Dysart e£_§I, (1973) present data on these collections (summarized in Table l) to indicate the general status in Europe of the three significant larval parasites with respect to constancy, occurrence at high and low host density, dominant parasite species, and mean percent parasitism based on examination of pupal cells after larval rearing. In addition, Andersen and Paschke (1968) give a biological sketch of the egg parasite, g, flavipes, and Dysart E£Mfll° (1973) describe the biology of each of the larval parasites. Some of the salient biological features of each parasite are summarized in Table 2. Dysart g£_§I, (1973) discuss interaction between species of the larval parasites in Europe and note that when more than one egg of 2, carinifer occurs within a host (superparasitism) only one larva survives. They presume this to be the case with the other solitary ichneumonid, I, gpgggg, Competition exists between 2, carinifer and I, 12312: Dysart EEHEE° (1973) note that Q, carinifer supercedes I, igII§_if both are in the larval stage within the host. However, the larvae of I, julis may be able to compete with Q, carinifer if an egg TABLE 1: Status in Europe of three larval parasites of Q, melanopus based on 44 collection sites (Adapted from Dysart SE 21' (1973)). Diaparsis Tetrastichus LemOphagus carinifer julis curtus Constancy* 100 91 73 (91)2 Occurrence at high host densities 100 83 100 Occurrence at 3 low host densities 70 (50) 50 10 Dominant S9 34 9 Average parasitism (range) 12.3 (.4-50) 10.4 (0-56) 5.6 (0-29) *All values in percent. parasites in European collection sites. 1 . . Taxonomic status 13 unclear. TI. curtus was not detected in the Iberian Peninsula. Constancy refers to the presence of 3Diaparsis sp. was only parasite detected in 50 percent of low host densities. .czocx prquHomEHv .ouoe xfinwmmomt-m:ofiumuocom 039 m .oocwnm chen930m cw mcofiumnoaom ozu ammoa u<~ .Hmex you macaumnocom Hano>omH :ooooo HHoo ago Have mqu gasp“: «Have omepm cm wanna cw :ooooo om>hm~ ovum v mcwuoucwzuo>o o: o: o: as memo: voNfiuflmwumm mo :ofluficwooom om>ha~ ummfi om>hm~ mm>hmH umma amen weaken one umhwm Mama on Hoflhm one umhwm Houmw Ham: cofiufimomfl>o xmom om>he~ Ham om>hmH afieam om>ha~ Ham mwo xaneo coconowonm oueum pmo: AhmuwHom aneuwHOm meownmmonm maoflumwonm mulomwoum no xymufi~om mocfiuao>wuase ocwumo>wcs mocwuflo>wu~=a flocwpao>fiuaza amficflu~o> nompwcoasoncoH nomowcossocnom mowvfigmoflsm fiomufihmaxz "enoumocwmxzv ”whoumocoasmy “snowmocwmxzv ”muoumocoaxmv msuhao .4 nomflcwnmo .o mafia“ .9 momfl>e~m ad ofiumfinouumnesu mowoogm ouflmMHma .mouwmmuaq Ha>haH may no nmhmav .mmzmm.uhamxa can opwmenem mum on» :o hwoafiv excomum use camnooc< an pogo: we encasm Scum wounome moufimmhem_mo muoomme “moflmoHOMD 050m mo meEESm < ”N mqm< .N .mwm m own m>o 1 mmo om>c04 .J mmo oocmmcoEm .I l. mc_cam m__:_ .H mocmmcee 4 cessam m__:w {H mocomcoEm 1 LmEEDm mmo 25 Specific activities involving measurements of population densities, behavioral parameters, emergence patterns, etc., occurred at different times during the study. Some of the activities involved sampling CLB densities in different areas, studying the development and behavior of I, julis, measuring emergence rates of I, quI§_under manipulated con- ditions, etc. Many biological characteristics of the parasite were determined at different times because at the outset of this study the biology of I, quI§_was imperfectly known. Table 4 attempts to give an illustration of the sampling activities conducted to determine the biology and significance of I, julis on CLB populations at Gull Lake. Gull Lake management plan. Co-operation between the Kellogg Biological Station and CLB research personnel was facilitated through a grant from APHS (now APHIS) fer land rental. The three areas of the Experimental Farm included within the context of this grant are shown in Figure 3. The intent behind this request was to have control over the crop configurations, planting dates, and the application of pesti- cides in these areas. Within these locations, plantings of winter wheat and spring oats have been manipulated with the objective of providing maximum potential for the increase of CLB parasites. The phi1050phy behind specific manipulations and variable crop planting dates was: (1) oat stubble should be protected because plowing may cause mortality of overwintering parasites, (2) winter wheat should be planted next to oat stubble be- cause the CLB population is usually found first in the winter grains and parasites emerging from oat stubble would have a short distance to travel to find hosts, (3) spring oats should be planted next to winter 26 TABLE 4: Field sampling activities in sections 5, 8, and 9 at Gull Lake. Activity 1970 1971 1972 1973 CLB 2population (ft2 samples of eggs and larvae, weekly) CLB sweep survey (larvae, 100 sweeps per field) julis density est. (emergence traps) I, julis daily emergence rates (emergence traps) 9 T. julis flight activity (flight traps) julis adult densities TD-vac) julis diapause incidence julis attack behavior 9 .julis overwintering estimate (soil sample) 14 8, 9 9,10 11 912,13 Em hasis between section CLB population densities regional CLB population estimate parasite distribution between areas rate of parasite emergence control of parasite emergence flight activity during summer generation flight activity during spring generation ‘OmVO‘U'l-bLRNr-I 10. field density estimates in oat stubble ll. definition of diapause through time 12. field observations on attack behavior movies of attack behavior 14. estimate of overwintering parasite density and mortality examination of effect of crop age on CLB density field density estimates during search for hosts 27 Fig. 3. Aerial photograph of the Gull Lake Biological Station and surrounding area indicating sections 5, 8, and 9 where detailed cereal leaf beetle research was conducted. 28 wheat for the reason in (2), and (4) late plantings of winter wheat and spring oats may provide late and/or additional CLB larvae to assist the increase in overwintering parasite densities. Through these manipulations it was intended to establish parasite densities of sufficient magnitude to facilitate re-colonization under field conditions rather than under laboratory conditions because of problems involved in laboratory production of the larval parasites. Variations of this scheme were carried out through 1974. The actual plantings and manipulations in the three areas are given in Figure 4. 29 mm a» any 2 U on aft-.1 -_~ * on: u; an 3 an 3 new 3 our 3 on sum: 3 an on m 3 an: 8 a I'm-u m. a: : mum on. an 3 _ an snuu 3 um on sun-u ‘ w‘ “A! . “‘y 2 . O' S W 2 m 1 w an ‘ I on 5m: 3 w: m s g ' 2 am “7‘ g a" = 8‘ “I "I_.! : U em out an! 3 our 3 g g Y O on? g on sin-u ’ new 3 um an M1 on out I on m: a nu? ' mou 1 5 out a an " 00' a an am out e on: g 0 a a un on m 3 a an mm: 3 1 1- _ 2- _ ,1 -g ' E 5 ° 2 5 9 1 5 a 5 l i Q " I 5 - - i g i i i 3 i 1 i i I c an m 2 v- m Dunstan 1'. out : .. __._ ._ o lultm not 3 ' an m 3 a “7! = ‘ um no? 3 mm: M. “A v 3 um em 3 - _‘ an man 8 on: 2 ~ an an ' “A! m 0-: - m' 8 um out ; - h g um '0' I on 5w 3 a on m g um an o ' °‘" 1 on m ‘ c- on mm: a “A, a- . I07 ' o a an (an a a n ‘1 I o g E o I I a i! o I L‘ 5 ‘5‘; 2 i i ' E 3 2 Q t E I ‘ 2 ‘ l E z i i i I i ‘ B .. g u?! U?! o 2 .. 't) a. z .. on man 3 O - um we 3 am It” a 3 0-! 5m 3 " 3 w, 3 mm: m. Q g a a" 8 "he lean» 3 ~ L"! “A? R "t. Omm- 0; °" man: I an: urn-u : = I g on man 3 am 2 o um em 3: um no! 0 . “‘7 a a" C .- on; g on SW c c on M1 8 o a mu In" a - I l I g! , I n ‘ O i . a . E !; 533‘ 5!; ! gig fig}? 5 i i h E s i a “A! I. l’ CIIONIIII 2 on 2 “I "DJ 2 u?! on" = .4" 2 am a U7 “I! n U" 0‘.“ " “nun . hetero MI. "72 mm- I Tr‘lIor Fig. 4. Field maps of sections 5. 8. and 9 at Gull Lake indicating crop planting configurations used in management plans. RESULTS Development of I, julis under laboratory conditions. In spring, as the temperatures increase, the parasite larvae within the CLB pupal cell respond to a temperature threshold and initiate development. To determine the temperature threshold for development, Cage and Gage (un- published data) exposed I, ngI§_larvae, which had been stored at 40° F for 14 weeks, to several constant and oscillating temperatures. The incubators used consisted of water baths in insulated small plastic buckets. Temperatures were controlled using one or two aquarium heaters depending on whether or not oscillating temperatures were re- quired. For temperature oscillations, one heater was set to the lowest desired temperature and the other regulated with a stepping timer to increase at a desired rate to the maximum temperature and then to decrease at a similar rate until being shut off. The water baths were agitated with air and the temperature of each water bath was monitored using thermocouples and a 24-point potentiometer. The developmental period from overwintering (post-diapause) larva to adult stage at the different temperatures is given in Table 5. The number of days to complete the above development is transformed to % per day (l/x - 100 where x is the developmental period in days at each temperature). Figure 5 shows this relationship. The regression equa- tion estimates the developmental threshold temperature fer the parasite to be 47.l° F. 30 31 TABLE 5: Development of I, julis at constant and oscillating temperatures. Days go emergence Temperature XiSE % per day n Constant Temperatures C F 32.2 90* 29.4 85 12.16:.56 8.2 12 26.7 80 11.03:.11 9.1 40 23.9 75 14.48:.29 6.9 27 21.1 70 16.72:.31 6.0 29 18.3 65 22.71:.41 4.4 35 15.6 60 31.75:.49 3.15 8 12.8 55 43.75:.25 2.29 4 10.0 50** Oscillating Temperatures 80--90 (85) 12.01.58 8.3 6 70--80 (75) 13.14:.38 7.0 14 60--70 (65) 26.50:.43 3.8 6 *100% mortality. **No development after 55 days. 32 .mchEmaEmu pcmcmtg pm $23 mmsmafiuémoa Plan .H “6 Ann cog magic—min 28ch .m .9... mmm:... AVG 83d .LNBWdO'lZ-l/GCI .LNBOHBd 33 Because of the increase in developmental time above 85° F, the calculated line would have intersected the x-axis at a slightly higher temperature; but, since 48° F is used as the developmental threshold fer eggs and larvae of the CLB (Helgesen and Haynes 1972; Gage 1972), the 48° F threshold will be used as the parasite overwintering develop- mental threshold fOr ease of computation and generalization. In addition to measuring the total time for emergence to occur from the time pupal cells were removed from cold temperatures until adult emergence, within-stage development of I, jEII§_was examined at constant temperature (70° F). Parasite larvae were removed from CLB pupal cells and the developmental stages of I, iEII§_were arbitrarily visually classified into seven consistently identifiable categories: (1) larva, (2) larva with meconium, (3) larval differentiation into head, thorax, and abdomen, (4) pupa with white eyes, (5) pupa with red eyes, (6) pupa with black body, and (7) emerged adult. Figure 6 shows these various developmental stages of I, ngIs, This information was used as a method to bioassay development in the field and enabled accurate timing for setting out emergence cages to monitor adult Ih quI§_emergence and density. This bioassay was accomplished by collecting CLB pupal cells from the soil, examining I, ngI§_within the cells, and holding the parasites at 70° F. A comparison of development in the field with Table 6 enabled allocation of resources fer preparation and setting out parasite emergence cages. For example, if the average coded development from field-collected parasites was 3.5, then most of the population had developed to the white-eyed pupal stage and adjustments were made accordingly. 34 Fig. 6. DevelOpmental stages of l. Julis from diapausin larvae in cereal leaf beetle pupal cell (a) to an emerged adult 1?. 35 TABLE 6: Development of I, julis at 70° F from time of removal from storage (42° F) until adult emergence. Coded developmental Day stages of I, ngI§_ Code (n = 21) l 0 0 larva 2 .05 l larva with meconium 3 .19 2 head, thorax, abdomen 4 1.05 3 pupa—-white eye 5 1.76 4 pupa-~red eye 6 2.60 S pupa--black body 7 3.43 6 emerged adult 8 3.67 9 3.94 10 3.97 11 4.25 12 4.57 13 4.92 14 5.38 15 5.50 16 5.90 17 5.91 18 5.91 19 6.00 36 Daily emergence of I, julis and summer CLB adults. Emergence of I, ngI§_was monitored daily in specific sites during the emergence period at Gull Lake. This was done to study the synchrony of this parasite with its host; and, to enable prediction of’I, jng§_on a regional basis by quantifying emergence as a function of temperature, rather than limiting the observations to time alone. The most useful method for accomplishing this is to calculate degree-days (°D) above the developmental threshold of the parasite (48° F) and plot I} ngIs_ emergence over 0048- Since I, qu s overwinters in the soil at a depth of about 2 inches, development depends on soil temperatures at this depth. Soil temperature records are almost non-existant in Michigan (only 2 sites). For this reason, emergence of I, jBII§_was quantified using °D48 accumulated in the air. However, soil temperatures were measured at 2 inches so that conversions could be made if and when soil temperature infermation was available. Average weekly soil temperatures measured at Gull Lake are shown in Figure 7a. Figure 7b shows the relation- ship between weekly accumulations of °D under standard conditions (x) and at 2 inches in the soil (y) collected from the same sites. Table 7 gives the equations fer conversion of °D from standard air temperature 48 records to °D48 accumulated in the soil at 2 inches under undisturbed oat stubble and under oat stubble covered with straw. These relation- ships are linear but considerable variation exists because of variabil- ity in the amount of cover over each temperature sensor in the field. It is necessary to be aware that lag times exist between warming soil and warming air temperatures. Standardization of temperature recording sites would have reduced variability, but because of natural variability SOH.TEMPERATURES AT 2 INCHES (°F) 37 IOOOr fin,“3 FROM SOIL AT 2 INCHES I4CND 600 800 IOOO AIR cm, Fig. 7. Average weekly soil temperatures at two inches in oat stubble at Gull Lake (a), and the relationship between air 0048 and soil 0048 (b). 38 TABLE 7: Regression equations relating the number of degree-days accumulated above a threshold of 48° F (°D48) in air (°Da) to °D accumulated 2 inches deep in the soil (°Ds) at Gull Lake. Year Treatment Regression equation r2 1971 oat stubble °D = -109.9 + .95°Da .994 straw covered 1971 oat stubble °D = -180.7 + .74°Da .998 1972 oat stubble °D = - 80.7 + l.lO°Da .994 straw covered 1972 oat stubble °D = - 65.2 + .94°Da .994 1973 oat stubble °D = — 27.5 + .82°Da .999 straw covered 1973 oat stubble °D = - 58.9 + .63°D .982 a 39 in cover this would not have proved meaningful. It was concluded that this variability could at least be averaged within a field by proper distribution of emergence cages. This difficulty and inadequate regional information on soil temperatures led to the use of air temperature infermation for analysis of emergence. I, ngI§_has two generations per year; the first emerges from the past season's oat stubble, and the second emerges from the current crop after attacking CLB larvae feeding in the crop. After the emer- gence of the overwintering generation had been monitored, the traps were moved into the growing crop. The timing of this move was critical: if the traps were moved too early, then larvae in the crop would be protected from attack; and if moved too late, emergence of the second generation would be missed. To time the movement of the traps between generations, pupal cells were collected and parasites bioassayed to determine the state of development. After emergence of the second generation of I, 121133 summer CLB adults emerged and were trapped as they emerged from the current cr0p. In addition to measuring emergence in the spring from oat stubble, different methods were used to manipulate soil temperatures. For example, clear plastic was spread over oat stubble in 1971 to determine whether or not parasite emergence could be advanced by increasing soil temperature, thus providing a greenhouse effect. Straw was used to insulate the soil in 1971 through 1973, and it was hypothesized that emergence would be retarded. The,need for understanding the effects of different soil treatments on parasite emergence time stemmed from the possibility that the introduced parasites might not be well synchronized with CLB larval populations. If this were the case, some manipulation 40 might then be necessary to provide better synchrony, and hence, more efficient parasitism. Figure 8 shows comparative information for the spring and summer generations of I, igIIs, The emergence curves were defined by calcu- lating cumulative percent emergence. The solid lines through the emergence data (x) were calculated using probit analysis (Finney 1971). Although probit analysis has been primarily used for testing insecti- cides, a method similar to the one used here was used by Morris and Fulton (1970) to model the effects of heat units and heat requirements on the survival of Hyphantria cunea (Drury). The procedure for calcu- lating the cumulative emergence curve is as follows: probit analysis is performed on cumulative percent emergence and the resulting equation Ep = a + B °D is a linear transformation of the cumulative emergence 48 curve, where Ep is the predicted emergence in probits, °D48 is accumu- lated degree-days above a threshold of 48° F, and a and B are constants. After deriving the probit equation, the curvilinear cumulative percent emergence curve can be obtained by looking up the appropriate probit values which correspond to different percentages and rearranging the linear probit equation. For example, 5 is the probit value for 50%; 5 - a _ e 0 therefore, 8 - D48 represents the number of D48 the population has emerged. This equation can be solved for different at which 50% of percentages and will define the curves in Figures 8 and 9. In many cases the curves can be approximated by sight-fitting a line through the emergence data and reading the °D values directly from a graph. The probit equations calculated from emergence data in Figure 8 are given in Table 8. 41 firm? A. m>¢<4 040 \ \ wanna...» .50 ++ \ O o f?\a\+\. \ \\ 3x \ + 0 llllllll OI flan“ o o. 8592.. 3.3 H new. 002 oo~_ 00: 000. 000 000 8b 000 80 8* 8n CON 8. 1 1 1 1 1 4 1 1 1 1 u 1 1\. 1 1 1 1 d +\ I\— \O‘ I \\ ON + \ 32.5 \ ov \ . 29:429. \\ \ + 33 3&3 #2:: 39 \ 33:5 So \0 I I \\ 1v + OKOII' |l0|||0||||l0 8.3225 :3— H ~52 OOn. CON. 00: 000. com 000 usaoaem :6 853° . 0.51: 25.6 on 29.—341:2 m._.¢ CUMULATIVE PERCENT EMERGENCE 40» 20> A 1 L 1 1— 4 L A A A A A 1 #g A 900 IOOO H00 IZOO 1300 IOOO I500 I600 I700 IOOO DEGREE - DAYS I) 48’ F) Fig. 9a. Cumulative percent emergence of second generation I, julis adults and summer cereal leaf beetle adults in 1971 and 1972. l00~ 0A H + + * P + m 80- g I- g 60: + + K 40'- Iu _ / is :20- 4’+ E J 1 l 1 1 1 1 L a m 9 00 IOOO IIOO I 200 I300 O E l<)()” +. «f (L ,(DBI gfifi’T' m 80*- + 2 t l- 60_ < p / .J 3 40-- z I— + D 20.. O c) 1 l l l l I l l l 900 IOOO IIOO I200 |300 DEGREE -DAYS(> 48° F) Fig. 9b. Emergence of I, Julis adults from early (0A) and late (OB) planted oats in 1972. 42 TABLE 8: Probit equations, X2 values, and degrees of freedom for adult I, julis emergence curves shown in Figure 8. Ep is probit emergence and °D48 is accumulated heat above 48° F (air temperature). Year Treatment Probit equation X2 df 1971 Clear plastic Ep = - .47 + .021°D48 3.0 9 Oat stubble Ep = - 4.82 + .019°D48 8.2 16 Straw _ Ep = -16.80 + .034°D48 16.5 5 Spring oats Ep = - 9.53 + .014°D48 12.8 9 1972 Straw Ep = ~10.30 + .027°D48 1.8 7 Oat stubble Ep = - 3.10 + .018°D48 4.9 16 Spring oats Ep = — 8.86 + .013°D48 1.3 15 1973 Oat stubble Ep = .71 + .008°D48 3.6 28 Spring oats Ep = - 9.35 + .013°D 2.2 14 48 43 In Figure 8, oat stubble represents the untreated condition com- pared to clear plastic-covered oat stubble and straw-covered oat stubble. The deviation from 50% emergence in oat stubble caused by covering the soil with clear plastic was 254°D , or an 18 day difference in 1971. 48 Straw, on the other hand, delayed emergence by 148°D 8’ or about 7 days. 4 Straw had a similar effect in 1972 but the delay was less because of a lighter straw cover. The dotted line (Figure 8) represents cumulative percent occurrence of CLB larvae in oats. Parasite emergence from normal oat stubble is well synchronized with the occurrence of CLB larvae. Note, however, that the second generation of I, iuII§_does not begin to emerge until over 90% of the CLB larvae have pupated (Figure 8). The second generation of I, quI§_is shown in contrast to emergence of summer adults of the CLB in Figure 9a. Note that I, jEIIs_is still emerging when emergence of CLB adults starts. This indicates that many I, iggI§_adults are present after larvae have all but disappeared. Figure 9a also indicates that attack by I, iuII§_ occurs over a relatively short time interval due to I, igIIsfs short life span, compared to the extended period of oviposition and longevity of the adult CLB. Emergence of I, iuII§_was also measured in oats planted two weeks apart in 1972 to test if differences in the time of emergence could be detected. The parasite emergence curves in Figure 9b show that crop age had little effect on parasite emergence time, although, as will be shown later, the density of emerging parasites was different because of host selection by CLB adults. An average adult I, ngI§_emergence curve was developed from data collected daily during the first and second generations in 1971-1973. 44 The °D48 at which each of five levels of cumulative percent emergence occurred in each year for both generations is given in Table 9. The average values for the three years are graphed in Figure 10. The average values from Table 9 can then be used as an estimate of parasite emergence on a regional basis by using °D accumulated at different 48 weather stations in the region. This aspect will be developed further in a later section. Emergence trap efficiency. Tests were made to determine the capture efficiency of the emergence trap. Three traps were used and the foliage (oats) within each trap was cut to a different height. Male and female I, igII§_which were reared in the laboratory were placed in the cages at 10pm and the cages were checked until no more adults were captured. Prior to release, the parasites were sexed and placed in petri dishes. Twenty—five of each sex were placed in each dish. The dishes were placed in the cages at night. In the morning the dishes were removed and the parasites which died in each dish were counted and subtracted from the total released. Table 10 shows the number of I, igII§_captured at different foliage heights. The trap efficiency for females was 84% for the three foliage heights and was independent of foliage height. For males, the efficiency was less (39%) and dependent on feliage height. Male I, iuII§_adults are more delicate than females and, in the laboratory, females live longer than males: about two weeks fer females compared to three days for males. The same appears to be true under field conditions. 45 TABLE 9: Degree-day values for different percent emergence of adult I, julis during the first and second generations (1971-1973). Percent ._ emergence 1971 1972 1973 X180 First Generation (Oat Stubble) 5 415 355 350 373136 25 470 410 475 452136 50 500 450 565 505158 75 535 485 650 557185 95 585 590 735 636185 Second Generation (Spring Oats) 5 925 950 955 943116 25 1000 1030 1050 1027125 50 1045 1075 1100 1073128 75 1090 1125 1155 1123133 95 1165 1200 1230 1198133 46 nXum_ .mcoqumemm ucoomm 2:. “we: 9: 3.2% 333 $3“. .H yo 85395 .28ch 333353 mmmcmzq A... owe: m> O 14.43 00 C-IJ 0Q) (.00) .,_q_ S. (00 0-3 E44 0 ()0. CO L ’4) N r-I-F’ .C '03 U)"- .FF u.“- 52 The flight activity of I, luli§_adults is a function of many factors. To estimate the temperature threshold at which flight could be sustained, a regression line was calculated on the number of I, julis caught daily over a 9 day period in a flight trap rotating 2 ft. above the oat crap, and mean temperature during the daily trapping period (Figure 13). The equation shows that the sustained flight threshold is about 60°F. Activity within the crop, as opposed to above it, did not seem to be affected by average temperatures as low as 63° F, but observations in the laboratory indicate that activity is severely re- stricted at 55° F. Juillet (1964) studied the influence of weather on flight activity of 2 Families of Hymenoptera, Ichneumonidae and Braconidae, during three field seasons (April - September). He found that (1) maximum tempera- ture was a significant indicator of flight activity; (2) an increase in humidity favored the flight activity of ichneumonids while it re- duced that of braconids; and, (3) winds of low velocities stimulated flight activity and high velocities depressed it. These factors also influence the flight activity of I, 12115; but, rather than attempting to model specific activity as it relates to differences in weather, the activity was monitored at different trap heights to obtain some idea about the potential dispersal qualities of I, iEfliE: The general influence of trap height on the percent of I, igli§_caught at different heights is shown in Figure 14. A perspec- tive view of the effect of trap height on the number of I, 1211: caught per day is given in Figure 14a, which shows the total number caught in relationship to time and trap height (4 levels) above oat stubble during the first generation. This shows that as trap height 53 .mpmo mewcam emucm_q XFme m>onm ummm Lao; not“ pgmwpa xcwuoc m c? pgmzmu mu_:um mw_:n aH co conga: ucm nowcma mcvaumcu mg» mcrcsv waspmcmagmp came cmmzpmn awgmcowumpmc mg» .mfi .mwm mmm3H 54 Fig. 14. A perspective view showing the influence of trap height (2) on the number of adult I, ulis caught above oat stubble (y) during the first generation (x). Figure b) shows a similar perspective of adults caught during the first and second generations above wheat and oats. 55 increases, catch decreases. A portion of the pepulation of I, igli§_ is trapped above the oat stubble and this component of the population is actively dispersing to nearby wheat or oat fields, or is being dis— persed passively by wind to other areas. Figure 14b shows a similar relationship, but these data were obtained from within and above a ‘wheat and oat field. In this case, the numbers caught represent the number of individuals moving through or above the crop and represent a.component of dispersal or active searching, especially during the first generation when the population has moved from oat stubble, where it emerged, to the crap where hosts are located. The first and second generations of I. julis are well delimited in Figure 14b. Attack behavior of I, julis. Observations in the field including ‘time lapse photography led to the structuring of I, igli§_attack be- liavior from the time the adult female had detected its host and had selected the larva fbr potential oviposition until the attack was com- ]olete and the parasite left the host vicinity. I have divided attack loehavior into five components: (I) approach, (2) mounting, (3) posi- tion selection on larva, (4) oviposition, and (5) dismounting and cleaning. After a larva has been detected, the adult female may walk up and down the leaf on which the larva is feeding. Eventually the parasite approaches to within ca. 1/4 inch of the larva and remains motionless for about 5 minutes (Y'= 4.93 i 1.60). During this time each antenna is moving alternately at about once per second. The body position may be changed during the approach period depending on whether or not the larva is moving as it feeds. After the approach period, the parasite 56 attempts to mount the larva. Some larvae do not react to the mounting parasite while others lift their abdomen up and down while clinging to the leaf. During mounting, the parasite lifts her wings vertically over her thorax to avoid becoming stuck to the viscous fecal coat on the back of the larva. The avoidance reaction by the larva may dis- courage mounting and the parasite may dismount and return to the approach behavior condition on the same larva or may discontinue the attack and leave the area. If the mount is successful, the female positions her- self to an area on the larva which minimizes disturbance by the abdominal movements of the larva. This position varies considerably. It may be on the back of the abdomen where movement is great, on the thorax just behind the head capsule, or on other locations such that the movements of the larva do not interfere with the act of oviposition. Oviposition takes place with wings held high over the thorax. The antennal movement during oviposition is slower and more deliberate than during the approach. Time needed to oviposit an average of 5.67 i 1.84 eggs/larva is 18.8 t 4.22 minutes. When oviposition is disturbed by larval movements, the act is discontinued and the female rarely con- tinues any attack phase on the same larva. When oviposition is complete the parasite dismounts from the larva and moves several inches away from the larva. For several minutes the female cleans her antennae, wings, legs, and abdomen. A schematic diagram of these activities is summarized in Figure 15. Broken lines in the diagram represent dis- turbance of the activity, and the direction of flow represents the repetition of the behavioral components or abandonment of attack. There are several factors which have been observed that cause attack abandonment or repetition of earlier behavioral components. 57 SEARCHING FOLIAGE . HOST LARVA DETECTED i—_€J APPROACH FOR CLB LARVAE AND SELECTED FOR T \ ATTACK i >1 MOUNTING OVIPOSITIDN SITE SELECTION __ ON LARVA r I I I l I l l .J OVIPOSITIDN k-<%----J g"“._--_--- DISMOUNTING I CLEANING Fig. 15. A schematic representation of the principal components of attack by I, julis females. 58 One of these, mentioned earlier, is the defence reaction (rapid abdomenal movement) by the larva. Unsuccessful attacks have also been observed when: leaf movement caused by wind touches the parasite while on the host, host drops to the soil or another I. julis female mounts the same larva. Laboratory assessment of I, julis fecundity. The determination of fecundity, the rate of egg production, and the length of adult life of I. igli§_were studied using several methods. The behavior of this animal is not easily investigated in the laboratory because of con- straints placed on its movement by the universe in which it is studied. In one set of studies, lantern globes placed over pots of barley on which CLB larvae were placed were used as the universe and adult I. 12115 were introduced and exposed to five hosts. Adult parasites were changed regularly but survival was low due to moisture buildup within the globes. In addition, the parasites generally spent most of the time on the gauze covering the top of the globe. To determine the proportion parasitized, the CLB larvae were allowed to complete development and pupate. This introduced an additional mortality source. After testing several types of universes, the one giving the most satisfactory results was a 6 in. cylindrical cage made from Lumite screen with a diameter of l in. The top and bottom were plugged with removable pieces of sponge. A young barley plant was placed through a slit in through the bottom sponge. Three third instar CLB larvae were placed on the leaves, and mated adult I, luli§_were introduced. The cages were kept at 70° F and were placed in a rack over a shallow water pan into which the roots of the plant seedlings penetrated. At 2-day 59 intervals the adult parasites were introduced to new larvae on fresh seedlings. CLB larvae were dissected and the number of eggs in each larva was counted. The fellowing data are based on 17 females. Figure 16a shows the average numbers of eggs laid per day by females which remained alive at the time females were transferred to a fresh cage. All females were still alive by the tenth day. Egg production peaked on the eighth day reaching a maximum of 9.5 eggs/2 days/female and decreased until day 26 when only one female was alive, and she laid 2 eggs. The cumulative number of eggs laid per female is shown in Figure 16b where 50% of the eggs had been oviposited by the eighth day. Eggs laid per female decreased after day 8 and female survival decreased linearly after day 10 (Figure 16c). The average longevity, eggs laid per day, and fecundity and range of each determined from the 17 females tested is summarized below: Longevity (days) l8.18:l.30 (10-26) Eggs/day/female 2.95: .29 (1.55-5.90) Total eggs/ female 59.5314.09 (28-84) These data may not be definitive because of the small number tested and the possibility that a better universe exists. Fecundity estio mates from earlier experiments indicated a maximum of 40 eggs per female; less than one-half of the maximum measured in these tests. Incidence of diapause in I, julis. CLB larvae were collected from fields throughout the season and placed on flats containing host plants. After pupation, pupae were removed from pupation medium and individually placed in small petri dishes. Emerging adult parasites or beetles were counted and removed daily. After emergence was complete, .Ilnl‘lllIllIlll.llIll.|l‘|'.III.\\II.I‘f 60 N 0) IO- (9 8 8 25» <1 c: CD 6" t3 ‘4 C) :5 __ <1‘4 3.; 2 <1 UJ :E O) O .b 0 no 0 CUMULAHVE EGGS / FEMALE ICX) 8C)“ 6C)” 4()” PERCENT SURVIVAL I 2() L l L o 4 8 :2 f6 20 24 28 DAYS Fig. 16. The relationship between days and eggs laid per 1, 'ulis female (a), cumulative eggs per female (b). and female survival (c) 61 the pupal cells were dissected to determine the cell content and the number of diapausing I, luli§_larvae was recorded. Figure 17 shows the percentage of I, iuli§_diapausing. Points prior to 650°D in Figure 17 result from larvae collected from winter wheat fields, and points after 650°D result from larvae collected from spring oats. This was because larvae are found first in winter wheat and later in spring oats. It is also during this period when adults of the first generation of I, igli§_have completed attacking CLB larvae. Few T} jpgi§_adults are present during 650-800°D and the number of larvae being parasitized during this interval is low; therefore, an estimate of diapause is dif- ficult during this time. There is an obvious switch from a relatively low proportion diapausing prior to 650°D to a high proportion entering diapause after 750-800°D. There are several factors that may be responsible for the induction of diapause including the influence of photoperiod, the age of the ovi- positing female, the number of eggs oviposited in a larva, etc. Prob- ably, it is a combination of several factors. In several instances both diapausing and non-diapausing larvae have been found within the same CLB larva. It is not clear whether the female has control over diapause or as the number of larvae within a CLB larva becomes larger than some threshold, diapause is not induced. Table 12 compares the number of non-diapausing and diapausing I, jggi§_in CLB pupal cells collected at different dates during the field season. The number of individuals per cell averages consistently higher in non-diapausing I, 12112: Table 13 compared the distribution of individuals within pupal cells where the laboratory reared individuals 62 00m. 00_ _ 000. 6.83m 93 ”5296.25. 3223; E 32;. .H 08 “:8ch Eomekvméo mmmouo com com 8“ com com .NH .mwm 00¢ ON 0? SI‘Iflf‘ 'J. .LNBOHEId 00 0m BSflVdVICI NI 00. 63 TABLE 12: Comparison of the number of non-diapausing and diapausing I, julis in CLB pupal cells collected at different dates. No. of I, julis per cell Collection date °D48 Crop Non—diapausing Diapausing 5/27/72 486 W 8.50: .39 (58)* 4.60:.60 (10) 6/ 4/72 618 w 8.67: .43 (54) 4.43:.79 (7) 6/ 4/72 618 W 7.84: .20 (51) 5.50:.54 (10) 6/11/72 732 O 7.46: .37 (11) 5.00:.86 (6) 6/11/72 732 O 6.50: .62 (6) 4.67:.56 (6) 6/27/72 1003 o 6.75: .48 (4) 4.54:.36 (26) 6/27/72 1003 0 8.60: .74 (5) 3.89:.30 (36) 6/27/72 1003 0 6.40: .93 (5) 4.16:.24 (38) 7/ 1/72 1094 O 8.29:1.39 (7) 4.00:.42 (24) 7/ 6/72 1172 O 5.40: .81 (5) 3.63:.26 (27) 7/ 6/72 1172 O 8.00:2.58 (7) 3.97:.27 (30) 6/ 2/73 533 0 8.41: .65 (32) 5.80:.41 (13) 6/ 7/73 641 O 8.25: .66 (12) 4.91:.39 (11) 6/14/73 813 0 9.50:1.56 (4) 4.43:.36 (30) 6/21/73 991 0 4.19:.22 (48) 6/24/73 1044 O 4.94:.44 (32) 6/26/73 1095 0 6.08:.66 (24) 7/ 1/73 1194 O 8.33:1.20 (3) 6.46:.67 (22) *Number of cells. 64 TABLE 13: Comparison of the percent frequency of I: julis individuals per CLB pupal cell from laboratory reared larvae (non- diapausing) with cells collected from the soil (diapausing). 1972 1973 No. per cell Non- Non- Diapausing Diapausing Diapausing Diapausing l 0 0 4.0 0 0 1 4 2 1 1 6.3 0 O 5 8 3 2 2 16.5 0 0 8 7 4 2 6 15.9 10 3 17 4 5 9 9 23.3 10 3 30 4 6 17.6 20.5 12.1 17.4 7 20.1 10.8 19.0 11.6 8 15 8 1.1 10 3 2 9 9 9 9 0.6 15 5 l 4 10 9.2 0.6 6.9 0.0 11 3.7 0.0 1.7 1.4 12 2.2 I 0.6 5.2 1.4 13 2.6 3.4 14 1.3 1.7 15+ 2.9 3.4 65 are non-diapausing and the soil collected cells represent parasites in diapause. The highest percentage frequency occurs at 7 and 5 individuals per cell for non-diapausing and diapausing, respectively. This suggests the hypothesis that parasites may diapause when they are large and have sufficient reserves to enable survival throughout the winter. Adults emerging from pupal cells vary in size depending on the number of individuals within the cell. To quantify this observation, the non-diapausing adults emerging from cells containing different numbers of parasites were measured. The measurements taken were total body length and head width. Figure 18 shows the regression of body length on a number of adults emerging per cell over a range of 4 to 23 adults emerging from single CLB pupal cells. Both male and female I. igli§_emerged from most of the cells and since a size difference was noted between sexes, Table 14 shows the mean body length (:SE) and head width of the parasites emerging from pupal cells. The regression equations for female and male parasites calculated separately are: female, y = 2.28 - .042x, r = .74, n = 207; and, male, y = 1.82 - .028x, r = .62, n = 96 where x is body length (mm) and y is the number of I, igli§_adults per cell. Size of the individuals is related to the number within a CLB pupal cell, and these results could relate to the significance of the number per cell-diapause relationship stated earlier. This hypothesis was not tested but could proceed as follows: the overwintering parasite adults are larger and may lay more eggs per individual. The greater the number of eggs laid in a CLB larva, the less likely the progeny will enter diapause. The average size of the second generation of adults is smaller and they may lay fewer eggs, resulting in fewer 66 .592 .63 6:3,... .H :2; E... :8 $63 6368 68— :8ch .66 95%. .H mo amass: 65 5653 255.526.. 2: .mH .9“. .38 33?. 30 En. was; em 8 m. N. m 6 o _.l_ .1 dI 1 q 1 d d u 4 u d I P n 1N; —|_I... 5 iv; V m .04 D . . .l m. m mom": . 8.1 6 6 6 now moi xvvofvoudi . H LNN ) W W 67 TABLE 14: Mean length and width of female and male I} juli§_which emerged_from cells containing different numbers of para— sites (X : SE(n)). Female Male #/ce11 L(mm) W(mm) L(mm) W(mm) 4 1.96i 02 .64:.01 (4) 5 2.20: 06 .59:.01 (10) .63i.06 .51:.01 (S) 6 2.08: 06 .60:.01 (15) .711.13 .54:.02 (3) 7 l 85:.04 .58:.01 (20) 8 1.97:.03 .60t.01 (41) .62:.04 .52:.01 (7) 9 1.93:.03 .59i.01 (33) .77:.05 .S4i.004 (12) 10 1.87:.02 .SS:.01 (27) .54:.03 .48i.02 (13) 11 1.77:.03 .S4t.01 (l7) .34i.06 .43i.01 (16) 12 1.64:.04 .51:.01 (15) .37i.03 .45:.01 (9) 13 1.86:.03 .52i.01 (5) .57:.03 .48:.01 (8) 19 1.46: 02 .46t.01 (ll) .27i.02 .44i.01 (8) 23 1.36: 03 .43t.01 (9) .22:.04 .39t.01 (l4) 68 numbers of eggs per larva. Diapause would increase as CLB larvae would contain fewer parasites and each parasite may have more energy reserves to enable high overwinter survival. No evidence of this mechanism was found in the literature. It is, perhaps, as likely that the female has control over diapause as suggested by Simmonds (1946) who found that as the female of a chalcid, Spalangia drosophilae, Ashm. (Spalangidae), grew older, there was a progressive tendency fer more of her progeny to enter diapause, even though external conditions were kept constant. The importance of maternal origin and diapause was also noted by Saunders (1964) for the parasitic wasp, Nasonia vitripennis. I, igIIs is a difficult species for studying this phenomenon in the laboratory because, usually, most of the first generation progeny enter diapause. This problem prevented mass rearing of I} quI§_for subsequent release and, until more research is completed which defines the factors controlling diapause, it is only feasible to define the proportion of diapausing parasites in the field. Mortality of I, julis and CLB in the soil. In 1971, unusually high numbers of dead I, julis larvae and adults were found within pupal cells of the CLB. A large proportion of CLB prepupae, pupae, and adults were also dead within the cells. Table 15 summarizes the rain- fall and heat (°D accumulated during each month (April - July) for 48) the years in which CLB population estimates were made (1967-1973). Note that rainfall was more than one standard deviation from the mean in April and June, 1971. Rainfall during May 1971 was also less than the mean, resulting in a dry period (April - June 1971) compared with 69 TABLE 15: Total rain (inches) and °D43 per month (April -July) for the years population density estimates were made for the CLB at Gull Lake. April May June July Year Rain °D48 Rain 0048 Rain °D48 Rain °D43 1967 4.73 151 2.34 250** .03 667 2.88* 669** 1968 2.95 178* 3.25 284 .59* 608 .37 727 1969 4.95 157 2.79 369 .60 492** .47 759 170 3.45 164 4.09 442* .62 619 .87** 768 1971 1.14** 135 2.33 328 .63** 747* .64 700 1972 3.39 104** 3.79 421* .70 528** .94 721 1973 3.71 143 6.06* 275 .63 667 .76 770* 2' 3.48 148.0 3.52 338.4 .26 618.3 .70 730.6 SD 1.26 23.4 1.31 74.6 .85 87.1 .08 37.9 7:50 2.22 124.6 2.21 263.8 .41 531.2 .62 692.7 2450 4.74 171.4 4.83 413.0 .11 705.4 .78 768.5 * > 1 SD. ** <1 SD. 70 the other six years. The accumulated °D48 during June was greater than one standard deviation above the mean, indicating that June 1971 was hotter than the other six years. Figure 19 shows the maximum average air temperature for 1967-1973 and the maximum air temperature in 1971. Total CLB larvae are indicated by the open circles. The period during June 1971 which was most detrimental to survival in the soil was be- tween June 16 and June 30 when temperatures were above 85° F. Soil temperatures were measured at 2 inches in the oat crop from 4 p.m. on June 28 until 4 p.m. on June 30, during the period of highest maximum air temperature. Soil temperatures reached 119, 118, and 114° F on each of the three days. Table 16 summarizes the percent mortality of CLB and I, iglis, Accumulated °D8s is used as an index of heat causing mortality in the soil. However, without the combination of low rainfall and high heat, mortality would probably not have been as severe. Rainfall during April and May may also have to be taken into account because of potential stress placed on the host plant. The resulting poor fOOd quality may also have been a factor contributing to low pupal survival. The effects of manipulating the soil on I, julis. Some of the treatments used in this study are important from the perspective of farm management practices, whereas others are useful in determining, from a research standpoint, which treatments enhance or decrease sur- vival of I, igIIs, For example, it is quite common to plow oat stubble to prepare the land for seeding to another crop like corn, winter wheat, or alfalfa because this is an accepted agricultural practice. Alternately, it is unlikely that a farmer would cover oat stubble with 71 .mnmfiunmmfl .Ezswxme x_wmu mmmcm>m mg“ op 66.66508 Axv Humfi mfisq XFme 6cm mean mascau mgzumcmaamp awn prmn Easwxmz .mH .mwm m2:... 0 v 0m mm mm m_ E 0_ 0 N G C G 1 d d ‘ d O .1 d 350. lhmm: z 48‘F) wheat and spring oats. 1967-1969. Cereal leaf beetle egg and total larval densities in winter Itil‘lliilllllllltlllll!III IOO 80 60 40 20 2.4 oeusrrv PER "3 T T 7 T T ' T T T r 78 WHEAT '00 80 60 40 20 I972 so WHEAT I973 200 400 600 . A 240 200 I60 .. 1 50 I T T T 40 30 I T r T T r T T f . r N ITTTTTI 900 000 I200 CAT 5 I970 I97l I972 (MWS I973 ”do A A .n‘ 200 400 600 800 IOOO IZOO I400 DEGREE-DAYSI>4B’F) Fig. 200. Cereal leaf beetle egg and total larval densities in winter wheat and spring oats. 1970-1973. 79 TABLE 18: The initial, peak, and last CLB egg and larval populations in spring cats with respect to °D48. Spring Oats Year Area Eggs Larvae First Peak Last First Peak Last 1967* 9--E** 1968 9--E 200 441 1000 400 780 1150 1969 9--E 256 519 1100 425 767 1225 1970 9--E 225 546 990 400 750 1225 1970 8--E 200 550 1000 400 790 1225 1971 9--E 150 330 970 350 660 1200 1971 5--E 172 425 1100 350 660 1300 1971 8--E 172 330 1100 350 590 1200 1972 9--E 100 380 1000 300 690 1150 1972 9~-L 150 450 1100 375 690 1200 1973 9--E 300 700 1200 400 850 1300 Y:SE 193:18 467:36 1056:24 375:12 723:25 1218:16 *Insufficient number of times sampled. **Numbers refer to management plan maps in Figure II and E or L specifies early or late planting of the crop. 80 were extrapolated to the initial and/or end points. The means (°D48) from Table 18 provide estimates of °D48 for sampling CLB eggs and larvae in spring oats, or for manipulating the population in various ways depending on management Objectives. Differences in 0048 accumu- lated befbre eggs or larvae are in the field may tend to cause variabil- ity between years (i.e., °D48 accumulated during March). Peak to peak differences reduce the variability but are not particularly useful for predicting when to begin sampling the populations. To quantify the seasonal population densities of eggs and larvae (Figure 20) the area under each of the pOpulation curves was determined by calculating the area between each sampling point and summing these areas fer the season. The approximation used fer determining each component area was Simpson's Rule (Crowe and Crowe 1969). The result from this integration gives the total number of individuals for the season on a °D48 basis. To correct for the developmental time of an egg or a larva, the total area was divided by the appropriate number of °D48 necessary for an individual egg (160°D48) or all larvae (220°D48) to complete development. This technique was given in Southwood (1966) who coined the term "total incidence method" for the analysis. The total area under the curves of eggs and larvae sampled at successive degree-day intervals during the season, divided by the appropriate developmental times, gives the number of eggs and larvae produced per ftz during the season (Ni). t ft" DCX) (4x) = total incidence = i developmental time developmental time where Ni is the number of individuals produced, t to tn are the times 1 at which the population was sampled, dx is the number of individuals at 81 each sample time, and developmental time is the number of degree-days it takes an individual to pass from one stage to the next at some threshold temperature. To define the papulation curves of eggs and larvae it is necessary to sample at frequent intervals throughout the season. This is usefu1 to examine synchrony of the populations in different crops, etc., but not practical if many fields in many dif- ferent areas must be sampled. However, if eggs and larvae can be sampled during peak densities, the total incidence can be predicted. Results from the analysis of CLB density measurements taken in a field of winter wheat and a field of spring oats each year from 1967-1973 in section 9 at Gull Lake are graphed in Figure 20a and 20b. Calculations made on these data are presented in Table 19a. Peak population den- sities occurred in 1969 for both spring oats and winter wheat, and only in 1969 did densities of eggs in wheat occur in greater numbers than in spring oats. Larval population densities have been decreasing since 1969 and have reached densities in 1973 below those in 1967 when densities were first measured at Gull Lake. These population data are given in Helgesen (1969) for 1967-1969 and in Gage (1972) for 1970. Appendices I-VI summarize the CLB population data collected during this study (1971-1973). Changes in larval population densities are expressed in column IL in Table 19a which is calculated by: IL a NL(t+1)/NL(t) where IL is an index of the change in larval density, NL is the number of larvae per sq. ft., and t is time in years. The trend in larval density has been generally decreasing in cats but erratic in wheat, especially between 1968-1969 when larval densities increased 140 fold. 82 TABLE 19a: Population density in spring oats and winter wheat per ft2 per season of CLB eggs and larvae (total area under seasonal population curve % developmental time), trend index of larval density (NL(t+l /NL(t))and the ratio of eggs per ft? to larvae per ft2 in tae same section in different years at Gull Lake. No. 2 2 2 Larvae/ft2 Year Samples Ft sampled Eggs/ft Larvae/ft IL Eggs/ftlfi Spring Oats 1967 S 30 31.7 19.4 .612 3.97 1968 16 30 110.0 77.1 .701 2.57 1969 13 30 378.6 197.9 .523 0.66 1970 8 30 203.4 130.2 .640 0.74 1971 7 15 275.0 95.9 .349 0.35 1972 10 15 86.8 33.7 .388 0.12 1973 9 30 10.1 4.0 .396 Winter Wheat 1967 6 30 2.7 1.4 .519 0.86 1968 14 30 4.5 1.2 .267 140.4 1969 12 30 412.8 168.5 .408 0.43 1970 8 30 198.1 72.6 .366 0.02 1971 8 15 24.1 1.4 .058 1.00 1972 6 15 3.7 1.4 .378 0.86 1973 6 30 2.0 1.2 .60 83 Densities of eggs and larvae are shown graphically in Figure 20a and 20b and the larval trend index IL is shown in Figure 21. The ratio of total eggs to total larvae (SL) is shown in Figure 22. Figure 23 illustrates the changes in egg and larval densities in oats in the phase plane by plotting successive densities (total inci- dence) over the fellowing year's estimate. The trajectory of the population is in the direction of the arrows on the lines in Figure 23. This illustration is useful in depicting the course of the densities from 1967-1973. The level of the CLB density in 1972-1973 is at its lowest point since sampling began and the next few generations will determine if the CLB will respond positively (densities will increase) or not. A positive response is indicated by egg densities from 1970- 1971 but this response was not reflected by the larval population which responded negatively during the same time interval. Population densities were measured in different areas at Gull Lake within the same year. A similar analysis was perfbrmed on these data to enable comparisons within years to show differences or similar- ities in density between fields with a year (Table 19b). One feature which is significant is the low larval/egg ratio in 1971 compared to years preceeding 1971 fer oats and in all years for wheat (Table 19a). An attempt to explain this is important because mortality due to para- sitism by I, ngI§_does not occur during the larval stages but during pupation; and I, quI§_was operating in 1971. Theoretically, feur factors could cause unusually high mortality of the CLB in the larval stage: (1) lack of food, (2) environmental phenomena (e.g., extreme heat), (3) high egg mortality, or (4) changes in population quality. Because densities were higher in earlier years with a correspondingly 84 «Km. .mumo m:_gam new pews; gmucwz c? xmnc? 626;“ ED» Nb? (.0. 0x0. 000. Fm>cmp mewmn mmmp ~mmcmu ._.LmF mPpmmn emm_ megmo mo owpmm mam» MNQ use (.9 0N0. 000. 000. N09 .2ng 55.3 x 6. . $3 625% 6 N N U) °r— Ll. BONBGIONI 993 / 30N3CIIONI 'IVAHV'I 86 .mmmfl-ummfl .mumo mCVLQm a: mum can auvmcmu Fm>LmF 6:6 mam Fmpou m_ummn emmp meLmu mo po_a amend .mm .mwm A: >tmzm0 20_._.m<._ x 00130.. meow 6 .m 3%: mead ez_mdm 0 N 006 87 TABLE 19b: Population density in spring oats and winter wheat per ft2 per season of CLB eggs and larvae (total area under seasonal population curve % development time) and the ratio of eggs per ft2 to larvae per ft2 in different sections and years at Gull Lake. 2 2 2 Larvae/f; Year Area Eggs/ft Larvae/ft Eggs/ftz Spring Oats 1970 9 203.4 130.2 .640 1970 8 368.1 199.4 .542 Winter Wheat 1970 9 198.1 72.6 .366 1970 8 211.6 112.1 .530 Spring Oats 1971 9 275.0 95.9 .349 1971 8 86.0 30.2 .351 1971 5 125.7 50.3 .400 Winter Wheat 1971 9 24.1 1.4 .058 1971 8 19.3 2.5 .130 1971 S 10.8 1.2 .111 88 higher larval survival, food alone is not likely the cause of the high mortality in 1971. High egg mortality had not been observed and Helgesen and Haynes (1972) indicated that egg mortality was constant. These factors, especially environmental phenomena and changes in popu- lation quality, need to be investigated thoroughly in subsequent re- search programs. Regional surveys are an important component of population studies on the CLB. Since densities of the CLB were measured several times during each season for a number of years in both winter wheat and spring oats at Gull Lake, it is useful to consider relationships which would enhance predictability of the occurrence of the CLB regionally, and enable prediction of total incidence from surveys of peak population density. This data could then be applied to regional survey data where sampling occurs less frequently. At the present time, attempts are being made to deve10p techniques for sampling peak larvae through use of on-line weather data. From such an estimate, seasonal CLB larval population curves can be constructed (Fulton personal communication). To test the ability to predict total incidence from peak density, 25 different populations of eggs and larvae in spring oats and winter wheat at Gull Lake (Table 20) were tested using this hypothesis. The relationships were linear and significant. Egg Incidence 3.51 + 1.85 (peak eggs) r2 = .98 1.63 + 1.51 (peak larvae) r2 = .96 Larval Incidence Although the total numbers of eggs and larvae are highly predict- able from the respective peaks, the value of this predictability in a control-management strategy is questionable because by the time peak larvae are determined, damage has already been done. However, the 89 TABLE 20: The relationship between peak egg and peak larval density per ftz, and the corresponding total incidence of eggs and larvae per season in spring oats and winter wheat at Gull Lake. Peak egg Egg Peak larval Larval Year Section Age density incidence density incidence Spring Oats 1967 9 E 10.8 31.7 11.3 19.4 1968 9 E 60.7 110.0 57.7 77.1 1969 9 E 185.7 378.6 152.0 198.0 1970 9 E 91.7 203.4 65.2 130.2 1970 8 E 176.6 368.1 106.0 199.3 1971 9 B 151.8 275.0 72.8 95.9 1971 5 E 58.2 125.7 32.7 50.3 1971 8 E 57.9 86.0 24.2 30.2 1972 9 E 56.2 86.8 24.3 33.7 1972 9 M 30.3 78.2 11.5 22.1 1973 9 E 3.4 10.1 2.6 4.0 1973 9 L 1.5 4.8 0.7 0.8 Winter Wheat 1967 9 E 1.6 2.7 0.7 1.4 1968 9 E 1.6 4.5 0.8 1.2 1969 9 E 245.6 412.8 106.3 168.5 1970 9 B 118.8 198.1 39.6 72.6 1970 8 E 103.3 211.6 70.9 112.1 1971 9 E 12.6 24.1 0.8 1.4 1971 5 E 4.5 10.8 0.4 1.2 1971 8 E 4.9 19.3 1.5 2.5 1972 9 E 2.0 3.7 1.7 1.4 1972 9 M 5.2 10.3 2.8 4.3 1972 9 L 21.9 33.3 6.5 10.9 1973 9 E 1.2 2.0 1.2 1.2 1973 9 L 1.1 2.1 1.3 4.0 90 predictability of total larvae from peak eggs allows some management action to be taken. The regression equation fer this relationship is: Larval Incidence = .90 + .87 (peak eggs) r2 = .88 The distribution of I, julis at Gull Lake. Initial releases of I, 12: s were made in section 9, field 13 and in section 5 (Figure 4) (Stehr, personal communication). In 1967, 148 I, ngI§_were released in an oat field in section 9; and in 1968, 430 IE quI§_were released in the same area. No parasites were released in 1969 (Stehr 1970). Since the initial establishment-recovery of I, ngI§_in 1969, many of the fields in the Gull Lake area have been monitored for adult I, julis using emergence cages, and for overwintering larvae of I, jEII§_by sampling soil and extracting and counting CLB pupal cells in which I, quI§_overwinter as larvae. Additionally, a sweep-survey was developed to monitor population densities in different fields at Gull Lake and to assess the impact of'parasites in each of the fields sampled. Historically, this study began in the fall of 1970. Emergence of the spring and summer generations of I, quI§_adults was recorded in 1971-1973. The rate of emergence was measured during these years and was reported earlier, but additional infbrmation on total number of I, quI§_adults emerging per yd2 from the previous year's oat stubble is provided from other oat fields which were measured in the area. The build-up of I, quI§_densities after the original recovery in 1969 was very rapid, but it occurred only locally. Table 21 shows the maximum numbers of adult I, ngI§_caught in emergence traps from oat stubble and the oat crop fer the spring and summer generations, re- spectively. The changing I, julis densities in the sections which had 91 TABLE 21: Mean number of spring and summer generation I. julis adults and CLB summer adults emerging per yd2 from several oat fields sampled in the three sections at Gull Lake. These estimates show the highest densities from the oat fields sampled in each section. No.* Spring No. Summer CLB Year Section fields generation/yd fields generation/yd adults/yd 1971 9 5 (31) 20.9 3 (25) 66.4 79.9 1971 5 s (21) 0.2 4 (12) 0.0 -- 1971 8 3 (14) 0.2 2 ( 8) 0.0 -- 1972 9 5 (70) 22.0 5 (45) 13.9 41.6 1972 5 3 (30) 0.0 1 ( 5) 0.8 -- 1972 8 2 (20) 0.2 2 (10) 4.6 -- 1973 9 3 (30) 20.9 3 (34) 15.6 2.1 1973 s 4 (40) 1.5 4 (20) 12.4 -- 1973 8 3 (30) 6.4 3 (15) 18.0 -- *( ) = no. sq. yds. sampled. 92 low densities in 1971 (sections 5 and 8) can also be observed in Table 21. This is evident from examination of the numbers of’I, ngI§_trapped during the summer generation in each section from 1971-1973. Also note that CLB densities declined significantly during these three years (see CLB adult production in section 9; Table 21). Production of I, quI§_ never reached densities in sections 5 and 8 comparable to those in sec- tion 9 in 1971 because of the decline in CLB density; but, by the summer generation of 1973, production in the three areas was comparable, indi- cating that parasite dispersal and build-up in the three areas had been accomplished by 1973. Crop age has significant impact on the production of CLB and I, qu13, Table 22 summarizes emergence data taken from crops of dif- ferent ages which were planted side by side. In spring oats, more para- sites are produced from the earliest planted crop, with production de- creasing as the age of the crop decreases. The opposite relationship is true in winter wheat where the later the crop is planted, the higher the production of parasites as well as CLB adults. The complete set of emergence data collected in 1973 is given in Table 23 and Table 24 to show the present densities of I, jBII§_and variability within each field sampled. By 1973, the parasite densities apparently became more unifbrm due to dispersal from the original re- lease site and build-up within each of the sections sampled. Additional infermation on distribution of I, ngI§_at Gull Lake was obtained by sampling soil, extracting the pupal cells of the CLB, and determining the number of'parasites which overwinter. This method of determining population density is useful in that it is an accumulation of the CLB population which completed feeding, and of parasitism at the 93 TABLE 22: The effect of crop and crOp age (early or late) on production* of T. julis (summer generation) and CLB adults. . . 2 I, lUllS/yd Year Crop Age CLB/yd2 n/field Female Male 1971 Oats E 8.7:8.7 1.3:1. 3 1971 Oats M 1.7: .9 0.0 3 1971 Oats L 0.0 0.0 3 1972 Wheat E .7: .4 0.0 1.5: .4 15 1972 Wheat M 3.7:l.2 .5: 8.0:l.7 15 1972 Wheat L 7.7:l.5 .9: 21.3:2.8 15 1972 Oats E 14.5:3.4 2.1: 12.8:2.0 15 1972 Oats M 12.6:3.l 1.1: 12.7:2.0 10 1972 Oats L 4.2:1.8 .2: 8.6:2.2 S 1973 Wheat E 1.8: .4 .8: 1.4: .5 5 1973 Wheat L 7.4:l.6 2.3: 1.0: .2 20 1973 Oats E 13.3:3 3 2.3:1 2.1: .8 10 1973 Oats L 2.2: .7 .6: .2: .2 S - 2 *X : SE/yd . 1E = Early planted oats or wheat M = middle planted oats or wheat L = late planted oats or wheat. 94 TABLE 23: Mean number of I, julis trapped from stubble at Gull Lake in different sections during spring emergence, 1973. I, julis/yd2 Stubble No. sq. yds. Section field Crop sampled Female Male 9 12 Wheat (E) 10 1.5: .6 1.6: .8 9 8 Oats (E) 10 l6.8:3.5 4.1: .8 9 18 Oats (L) 10 2.3: .7 0.5: .3 9 10 Oats (E) 10 9.4:1.9 2.7:l.0 S 53 Oats (E) 10 0.2: .l 0.2: .1 5 SS Oats (L) 10 1.1: .5 0.7: .3 5 60 Cats (E) 10 1.4: .6 0.1: .1 5 63 Oats (L) 10 0.8: .4 0.4: .2 8 ll Oats (L) 10 0.6: .2 0.2: .l 8 9 Oats (E) 10 5.4:l.4 1.0: .2 8 13 Oats (E) 10 2.6:1.0 0.2: .2 95 TABLE 24: Mean* number Of I, julis and CLB adults trapped at Gull Lake in different sections during the summer generation, 1973. I, julis/yd2 Field NO. sq. yds. Adult CLB Section no. Crop sampled Female Male /yd2 9 13 Cats (E) 19 5.5:1.4 1.3: .4 1.4: .3 9 15 Oats (E) 10 13.3:3.3 2.3:1.2 2.1: .8 9 9 Oats (E) 5 2.2: .7 .6: .2 .2: .2 9 7 Wheat (E) 5 1.8: .4 .8: .4 1.4: .5 9 11 Wheat (L) 20 7.4:1.6 2.3: .7 1.0: .2 5 54 Oats (E) 5 7.2:3.1 .8: .4 2.2: .9 5 61 Oats (E) 5 10.0:1.5 2.4:l.7 3.4:l.8 5 51 Oats (L) 5 .2: .2 0.0 .6: .2 5 59 Oats (L) S 0.0 .4: .4 .8: .5 S 56 Wheat (L) 5 7.6:3.6 1.2: .8 4.0:l.5 S 62 Wheat (L) 5 4.8:l.2 .6: .4 4.4:2.4 8 7 Oats (E) 5 14.0:5.4 4.0:2.8 5.0:].9 8 ll Oats (E) S 2.4:1.0 .4: .2 6.6:2.3 8 9 Oats (L) s .4: .2 0.0 1.2: .5 8 13 Wheat (L) S 2.4:1.9 1.2: .8 1.0: .6 96 end Of the season. It also provides an estimate Of the parasite popu- lation to emerge the following spring (after overwintering mortality). The soil samples do not account for the number Of cells that were para- sitized early in the season by I, ngI§_which emerge as the non-diapausing component of the parasite population. Attempts were made to categorize cells which had parasite emergence holes tO account for the parasitism during the first generation. This point will be discussed later. During the investigation, several methods Of soil sampling were attempted to determine the best method to use. Also, due to variabil- ity in elevation within some Of the areas sampled, the distribution of the CLB within the crOp would affect soil sample estimates of parasite density. TO test for a difference in CLB density, samples were taken on a hill top, a slope, and in a low area (Table 25). The variation in the numbers Of cells is high due to the small number Of samples taken, but the decrease in density on the slope was indicative Of low plant density due to low moisture in this area in 1970. TO account for these differences it was necessary to sample these areas within a field (if they existed) to account for the distribution Of the CLB. It was also important to examine the difference in crop age on the number Of cells found in the soil, which reflects the production of CLB and parasites (Table 26). More CLB and parasites were produced in the middle (M) aged oats compared with early (E) or late (L) planted oats during high CLB population densities in 1970. Different methods of sampling were tested in 1971 in early and late planted oats to determine which was the best method of sampling. One method consisted Of scOOping soil along the grain row to a depth of about 3 inches in 2 rows fOr 24 inches; the other method was tO drop a 97 TABLE 25: Differences in CLB production within a field depending on elevation differences (1970). Crop Hill top Slope Valley n Winter wheat 35.7: 9.0* 21.0:13.2 55.7:19.3 3 Spring oats 42.7:24.6 12.0: 3.5 58.0: 8.0 3 *Total pupal cells/é—yd2 (7': SE) TABLE 26: Difference in crop age on the number Of CLB and parasites produced (1970). Parasitized Crop Age Total cells cells Total I, julis n Oats E 74.0: 8.6 7.8:2.0 35.3: 9.4 10 M 110.0:12.4 12.4:3.3 55.3:13.3 10 L 25.8: 5.1 9.2:2.3 38.4: 9.4 10 TABLE 27: A comparison of two methods used to remove CLB pupal cells from the soil (1971). Parasitized Crop Method Total cells cells Total I, ngI§_ Oats (E) ScOOp* 30.0:4.8 12.2:l.8 23.2:4.3 1/2 yd2 47.2:2.8 16.2:l.7 29.4:4.6 Oats (L) ScOOp 8.6:l.7 3.4:0.7 ll.0:l.9 1/2 yd2 6.2:2.l 2.6:0.7 9.4:1.9 *Soil SOOOped to a depth Of 3 in. in 2 grain rows for 24 in. 98 1/2 ydz frame at random in the field (Table 27). Although similar production was estimated by the two methods, the more quantitative 1/2 yd2 method was continued fOr population samples. However, since the "soil scoop" method required less effort, it was used to collect parasitized cells for rearing purposes. The difference between the numbers Of CLB and parasites produced in and outside Of the emergence traps was examined to determine if the effect Of the cage was important. Soil samples (1/2 ydz) were taken after summer emergence was completed. Table 28 shows that parasite mortality was significantly affected in 1971 due to the emergence trap because plant growth within the traps was greater than in the uncovered crop, especially during dry periods (June 1971) when the crOp was pro- tected from direct sunlight and therefore less moisture was lost. The relationship between the mean number Of pupal cells recovered per 1/2 yd2 from 24 fields Of oats between 1970 and 1973, and the cor- responding standard error is shown in Figure 24. This relationship indicates that on the average the standard error was slightly above 10% Of the mean. The average sample size for these estimates was 10.2 one-half sq. yds. per field. Table 29 summarizes the estimates Of the number Of CLB pupal cells and the number Of parasitized pupal cells per 1/2 yd2 from oat fields in the areas sampled between 1970 and 1973. In 1969, Stehr (1970) estimated that there were 0.25 parasitized cells per 1/2 yd2 (l per 2 ydz). If this estimate is accurate, the parasite population increased 57 fOld in one year (1969-1970), although the build-up in 1970 was localized around the original release fields in section 9. In 1970, low numbers Of parasites were estimated from section 8 which is 99 .2665 6;» mo Lorre uceccebm ecu use we» r Log mfifimo Penna mo Longs: gems cmmzuma awcmcowpmfimg one .em .mwm «9%.. run. 938 .262 .oz 24m... 8. or oo 6.. om O q 4 d d d V. ( 301 3x, / swaowana )‘3'5 0 hm.uu._ X__.O+Nm. u> 9.‘ 100 TABLE 28: Differences in mean number and mortality Of CLB and I. julis during drought conditions when 1/2 yd2 soil samples were taken inside and adjacent to emergence traps in 1971. Parasitized Live Dead Condition Total cells cells I, julis I, julis Dead CLB Within trap 22.6:5.0 3.4:O.9 12.4:4.1 l.0:0.6 l.8:0.7 Outside trap 18.0:4.1 3.4:0.9 3.4:1.4 11.4:5.7 5.4:2.1 101 TABLE 29: Mean number per 1/2 yd2 Of CLB cells and mean number of cells containing diapausing I, julis larvae in samples taken from representative fields of normally planted oats in dif- ferent years in each Of three sections at Gull Lake. Parasitized Year Section Crop CLB cells cells n 1970 9 Oats 97.3: 5.6* l4.3:l.5 30 1970 8 Oats 109.5:11.0 .2: .2 10 1971 9 Oats 59.1: 8.1 4.9:l.0 10 1971 8 Oats 23.2: 3.8 .2: .2 S 1971 5 Oats 51.7:13.8 1.0: .7 6 1972 9 Oats 31.6: 4.0 8.4:l.3 10 1972 8 Oats 24.6: 3.3 1.3: .5 9 1972 S Oats 7.4: 1.6 1.8: .6 9 1973 9 Oats 5.1: .9 2.5: .6 14 1973 8 Oats 8.0: 1.3 2.8: .5 14 1973 s Oats 12.3: .9 4.1: .9 l4 *Y : SE / 1/2 ydz. 102 about 1/4 mile from the release site. An increase in parasite densities was expected in 1971, but estimates of diapausing I, quI§_larvae showed that the population decreased from 14.3 to 4.9 per 1/2 ydz. Earlier, Table 16 indicated the effect of high temperatures on I, ngI§_and CLB survival in the soil. Increases in the other sections were not signifi- cant fOr the same reason. In 1972, the diapausing parasite density nearly doubled even though the CLB pOpulation decreased by 1/2 in the release area (59.1 to 31.6). Parasite densities also increased in 1972 in the other sections and by 1973 the proportion of the cells which were parasitized in each of the three sections was high. Table 30 shows fields which were sampled in the three sections in 1973. The number of total cells produced is low, but the proportion parasitized is generally high compared with the total number of CLB per field. In 1973, the soil samples were taken in seven pairs down the field strips. These pairs were tested (paired—t) for significant dif- ferences of pupal cell density per 1/2 yd2 within each field. Only two fields of 14 oat fields sampled were significantly different at the 5% level. The same test was performed on the numbers Of diapausing I. fill—1.1.5. larvae and there was no significant difference at the 596 level within these fields. The impact of I, julis on the CLB population. The increase in denSlty of I, quI§_between 1969 and 1970 was very rapid in the original release site. Optimal conditions prevailed during this period due to high CLB populations which provided abundant hosts. In 1970, CLB densities were measured in the parasite release area and larvae were dissected to determine percent parasitism. Similar population density 103 TABLE 30: Densit; of CLB cells and density of parasitized cells per 1/2 yd sampled in July, 1973 in three sections at Gull Lake. Parasitized* Section Field Crop CLB* cells cells n/field 9 9 Oats (L) 1.3: .4 .6:.2 14 9 l3 Oats (E) 5.1: .9 2.5:.6 14 9 15 Oats (E) 7.7:l.4 2.4:.6 14 9 25 Oats (E) 6.9:1.0 1.3:.5 l4 8 7 Oats (E) 8.0:l.3 2.8:.5 l4 8 9 Oats (L) 1.9: .S .4:.l l4 8 11 Oats (E) 2.7: .6 .9:.3 14 8 32 Oats (E) 12.1:3.2 1.1:.4 14 8 34** Oats (E) 3.6: .7 .9:.3 l4 5 51 Oats (L) .9: .2 .2:.1 l4 5 59 Oats (L) 2.0: .5 .9:.3 l4 5 61 Oats (E) 12.3: .9 4.1:.7 14 *Y : SE. **Sprayed. 104 estimates were obtained in the primary release area in 1971 and, in addition, estimates of CLB densities and percent parasitism were made in sections 5 and 8 (see Figure 4). In 1972, similar estimates were made but an effort was placed on examination of the effect of crap age on CLB density and percent parasitism in section 9, rather than sample specific fields in sections 5 and 8 using the weekly foliage collection method. To examine CLB density and parasitism in these areas, a survey was conducted which allowed estimates of the above from several fields rather than concentrating on one or two fields in each section. In 1973, detailed population density estimates were obtained in section 9 in 2 wheat and 2 oat fields of different ages, as well as conducting an extensive survey in the 3 sections. A summary of within-generation CLB egg and larva population data collected at Gull Lake in section 9 is given in Figures 25a and 25b and in Tables 19a and 19b. Fields in which parasitism was estimated by larval dissection are considered in this section. Two aspects concerning parasitism by I} ngI§_became evident. First, parasitism was variable from year to year because of the changing state of the CLB population and I, jEQI§_densities; second, point estimates of parasitism within a season by I, ngI§_was not useful because of the dynamic interactions between the host and parasite. For example, percent parasitism reaches near 100% during the second generation of I, julis, At this point, larval densities are low and effective parasitism can only be reflected by examining the number of larvae parasitized per ftz. To determine the within season impact of I, quI§_on the CLB population, the area under the total CLB larval curve must be compared to the area under the parasitized CLB larval curve. 105 500' WINTER WHEAT o---o E068 N 400 x—x LARVAE L". E 300 CL C5 2 200 I00 500' SPRING mm b ‘;‘_ 400- :1: 53$er 0. ’ \ E 300- I ‘. CL. I, \\ I’lk C5 I ‘ I" ‘\ Z 200* ” X\ I ‘\ Ioo- 4' \x ‘6 Ky/x \x\‘~ . . . . .\‘3 I967 I968 I969 I970 I97| I972 I973 YEARS Fig. 25. Total incidence Of cereal leaf beetle eggs and larvae in winter wheat (a) and spring oats (b). 106 The dynamics of parasitism by I, 12:12.15 best illustrated by population data collected in 1972. This data set provides infOrmation on the temporal attack of CLB larvae by I, quI§_in different ages of wheat and oats planted side by side (see Figure 4d, section 9 fields 12-13). Figure 26 shows the effect of crop age on population levels of the CLB as well as the prOportion of the population parasitized by I, quI§_in each crop. Population measurements of CLB eggs, larvae, associated parasite densities, and the proportion of the larvae para- sitized were made in three ages of winter wheat, one age of mixed winter wheat and spring oats (Figure 26; oats a), and 2 ages of spring oats. Associated plant biomass infOrmation was also collected (Appendices I-VI). In the wheat-oat mixture, accomplished by disking a late-planted winter wheat strip and replanting to spring oats, CLB eggs on wheat and oats were counted and kept separate. The temporal occurrence of the populations of larvae and para- sitism by I, igII§_in different ages of winter wheat and spring oats is shown in Figure 26. Several features can be observed from this series of figures. First, the peak larval densities in wheat increase as crop age decreases. Also, in wheat, only the first generation of I, quI§_parasitizes CLB larvae. This is due to the drop in larval densities between 800-900°D and the initiation of the second genera- 48 tion of I, julis which occurs at 900-950°D Second, peak larval 48' densities in oats tend to decrease with a decrease in crop age. Para- sitism by I, julis adults occurs in oats during both generations (Figure 26). Percent parasitism in oats increases rapidly at the end of the larval population. The significance of this increase is not related to the number of larvae that are parasitized because the actual 107 WHEAT OATS 2.4 (I IOO :20 80 - i LG 60 - 1.2 I 408 ; «08 O I zo~ ; 404 l I 0‘ .CII/IIIIIIIIIIIIIIIIOIII. . , ~ 0 200 400 600 800 I000 I200 200 400 600 800 IOOO I200 I O x 2 X E; «50 I2 . 7 P- 'H I) 1) IL I: IooI «40 I00} «I0 5; 2 .o (3 80» ~ 8 El : -< 3.0 l U) 4 60~ 4 6 w m '. g 4 ~ 2.0 K 0- 40» ~ 4 q '2 . " w d "0 2° _ . I I) 7 2 3 E I In . MI 1 a 0 6II II I I IIIIIIIIIIIII ‘ 0- 200 400 600 800 I000 1200 200 400 soo 500 I000 I200 .4 6 “ '2 c C I00» 43 I00} «IO ‘\ BOI- « 4 80 ~ 60»- - 3 60~ 40 E a 2 40 P 20* «I 20» o 1 w I 1 I I l 2.0 400 600 800 I000 I200 200 400 600 800 IOOO I200 I400 DEGREE-DAYSI48‘FI Fig. 26. Total cereal leaf beetle larvae per ft2 in three ages of wheat and oats in 1972. with corresponding percent pargsitism by 1, Juli . Hatched areas indicate parasitized larvae per ft . PARASITIZED CLB LARVAE PER 50, FT, IIIIIIIIIIIIIIIIIIIIIIHIIIIIIIIIIII 108 number parasitized is small when compared to the total density per sq. ft. The importance is that the larvae parasitized during the second generation constitute a significant component of the parasites produced which enter diapause and overwinter. Figure 26, oats b represents the characteristic trend of parasitism by I, iuII§_in normally planted oats. The level that parasitism reaches depends on the adult parasite density searching fOr and attacking CLB larvae in the crop as well as the density of CLB larvae. The manage- ment plan at Gull Lake optimized the spacial arrangement of the crops with respect to the distance that I, iuII§_had to travel from its over- wintering site to the crop. TherefOre, I} quI§_females began to attack larvae in oats soon after initial emergence of the spring generation. Also, attack by the first generation of I, quI§_was most important because of the number of hosts available during the first generation attack phase (400-700°D) (Figure 26). The emergence of the second parasite generation does not occur until the CLB larvae attacked by the first generation have pupated and the parasites within the cells develop. Second generation emergence begins at about 900°D and may not be completed until 1200°D. By 1200°D almost all larvae in oats have completed feeding and have pupated. Peak CLB larval density occurs between the two parasite generations. Adult parasite densities were monitored using a D-vac to define the period when adults are searching in the crop and to establish the number of individuals searching. Adults are fOund searching in the crop as soon as they emerge from oat stubble. This situation was 109 optimized at Gull Lake by planting crops in strips adjacent to the over- wintering sites of I, quI§_(oat stubble). The period of peak density of adult I, quI§_during the first parasite generation in oats occurs just as CLB larvae are increasing; but, adult I, igIIs densities decrease prior to peak larval density. Adult I, iuII§_densities increase again due to second generation emer- gence as indicated by the curves of percent parasitism in Figure 26. In 1972, adult parasite density estimates were taken daily during the first and second generations of I, iuII§_in a field of mixed wheat and oats and in late wheat (oats "a" and wheat "c", Figure 26). The other two wheat fields were sampled only during the first parasite generation for adult I, quIs, and the late oat field was not sampled until the second generation (wheat "a-b" and oats "c", Figure 26). In each field, adult I} ngI§_densities were estimated from twenty ft2 samples. Density estimates of I, quI§_sampled on a particular day were averaged and plotted over °D48 (Figure 27). In each case, I, igII§_ adults were already in the fields when the first sample was taken, as sampling was done just prior to peak emergence from the soil. The dotted line in Figure 27 depicts the average incidence of larvae in oats and shows that the first generation of I, iuII§_Occurs prior to peak larvae and the second generation attacks only late CLB larvae. This compares with percent parasitism curves shown in Figure 26. The mean maximum I, iuII§_density in each field sampled in 1972 and 1973 is shown in Tables 31a and 31b. Note that peak parasite densities were higher in 1972. However, CLB larval densities were lower in 1973; so, to place adult I, iuII§_density in perspective, the ratio of CLB larvae to I, julis adults was calculated at peak parasite density to 110 00?. (°"'°) EAHOO "IV/\HV‘I 81C) .me>.ep oFHomn meow Femcmo mo mocmcgauoo come one .muoo newcqm use poms; Lopes; :2 up: Log Aopmcmo p_:om mr~3n .h apron coo: .nm .mwd An. omoAv m>gap mpgmmn 466— Pmmgmu co amass: mg» :mmzpmn awcmcowumFm; ace .mm .mwd ammgm \ m<>m<4 .Oz 0.. m. m. ¢. N. o 1 q q q N .O o _ .1 V no A V 3 om / 4.. . I. o hwhu. Z Nm.uu._ xm.~+m~.ou> 120 The most useful method of summarizing the data was to determine the number of CLB larvae and parasitized larvae per sweep per season by integrating the area under each of the pOpulation curves, as was done for the weekly population estimates. In cases where not all larvae were dissected, percent parasitism was used to estimate the number of parasitized larvae per sweep. Table 36 shows the CLB larval density, parasitized larval density, and effective parasitism fOr each of the fields sampled in 1972. In 1972, the numbers of I, igli§_collected during the spring emergence period indicated that few I} igli§_adults were produced in sections 5 and 8 (Table 21). This was substantiated by estimates of low overwintering densities of I, igli§_determined by soil samples in July 1971 in these areas (Table 29). The relatively high levels of effective parasitism shown in Table 36 suggest that a significant move- ment of I, juli§_adults took place from fields in section 9, which pro- duced as many as 20 I, igli§_adults per yd2 during the spring genera- tion, to sections 5 and 8. In addition, during the period when para- sitism began to increase in sections 5 and 8 (June 22-July 10) large catches of I, luli§_in flight traps indicated that dispersal of adults to these sections was occurring. In 1973, a similar survey was conducted, but this survey was expanded to include stubble fields from the previous year as well as other field classes of interest to other workers on the project. In comparing densities of CLB larvae in oats and wheat in 1972 and 1973 (Tables 36 and 37 a-b) a general reduction in population density is apparent. I, igli§_was removing significant numbers of larvae from the pepulation in 1972. Adult CLB immigration into the Gull Lake 121 TABLE 36: Density in different ages of spring oats and winter wheat per sweep per season of CLB larvae and larvae parasitized by I, julis (total area under seasonal curve % developmental time) and effective parasitism by I, julis in three different sections at Gull Lake in 1972. Larvae Parasitized % Parasitism CrOp Section Field /sweep* larvae/sweep (effective) Oats (E) 9 8 44.3 13.3 30.0 (E) 9 10 57.3 13.0 22.7 (L) 9 18 2.3 1.1 47.8 Oats (E) 8 9 88.9 21.1 23.7 (L) 8 11 13.7 2.4 17.5 (E) 8 13 53.4 6.6 12.4 Oats (E) S 53 11.2 1.1 9.8 (L) 5 55 6.1 2.3 37.7 (L) 5 63 0.84 0.36 42.9 Wheat (L) 9 9 3.4 0.33 9.7 (L) 9 15 1.9 0.34 17.9 Wheat (L) 8 7 3.2 0.29 9.1 Wheat (L) 5 51 4.7 0.19 4.0 (E) S 54 0.07 0.03 42.9 (L) 5 59 2.1 0.21 10.0 *Estimates based on 100 sweeps/field/sample date. 122 TABLE 37a: Density in different ages of spring oats per sweep per season of CLB larvae and larvae parasitized by I, julis (total area under seasonal curve % developmental time) and effective parasitism by I, julis in different sections at Gull Lake in 1973. CLB larvae Parasitized % Parasitism Crop Section Field /sweep larvae/sweep (effective) Oats (L) 9 9 0.24 0.21 87.5 (E) 9 13 1.31 0.74 56.5 (E) 9 15 2.16 1.27 58.8 (E) 9 17 3.97 0.53 13.4 (E) 9 25 5.30 1.99 37.5 Oats (E) 8 7 3.52 0.56 15.9 (L) 8 9 0.85 0.20 23.5 (E) 8 11 4.35 0.56 12.9 (E) 8 34 1.89 0.21 11.1 Oats (L) 5 51 0.06 0.0 0.0 (E) S 54 1.15 0.36 31.3 (E) 5 61 5.63 1.40 24.9 123 TABLE 37b: Density in different ages of winter wheat per sweep per season of CLB larvae and larvae parasitized by I, 'ulis (total area under seasonal curve % developmental time and effective parasitism by I, julis in different sections at Gull Lake in 1973. CLB larvae Parasitized % Parasitism Crop Section Field /sweep larvae/sweep (effective) Wheat (E) 9 7 0.20 0.06 30.0 (L) 9 11 0.46 0.29 63.0 (E) 9 19 0.34 0.16 47.1 Wheat (E) 8 8 0.70 0.31 44.3 (L) 8 13 1.32 0.75 56.8 Wheat (E) S 52 0.29 0.06 20.7 (L) 5 56 0.67 0.24 35.8 (E) 5 58 0.41 0.03 7.3 (L) 5 62 1.58 0.33 20.9 124 region was obviously not a factor between 1972 and 1973 because this would have been reflected in increased larval densities in 1973 but emigration could have been a factor. The increased removal of in- dividuals by I, juli§_from the population in 1973 further reduced popu— lation levels and, unless immigration into the area becomes a factor, populations should be extremely low in 1974. The impact of I, 12115 on the CLB population can best be sum- marized by examining the information contained within data collected from soil samples after CLB pupation occurred: Table 38 shows the ratio of cells containing diapausing I, luli§_larvae to total CLB cells per 1/2 ydz sampled from normally planted oat fields from the 3 sec- tions examined during this investigation. In 1969, Stehr (1970) re- ported a density of .25 parasitized cells per 1/2 ydz, and Helgesen (1969) estimated a density of 34.3 i 3.6 CLB pupal cells per 1/2 yd2 in an oat field where Stehr's samples were taken (section 9). Using these estimates, the ratio of parasitized cells to total cells is .007 fOr that field. The estimate fbr 1970 in section 9 (Table 29) shows a 21-fold increase in the proportion of cells parasitized by I, 13113_ between 1969-1970. Mortality of non-diapausing and diapausing I, igli§_ as well as CLB prepupae, pupae, and CLB adults caused by high soil temperatures in 1971 showed a decrease in the proportion of CLB cells parasitized between 1970-1971 in section 9. Parasitism by I, 13135 has been increasing at different rates in three sections because of differences in CLB densities in the fields sampled, and because of the dynamics of the crop. For example, the total number of CLB cells in 1972 was 7.4 in normally planted oats in section 5, compared to 31.6 and 24.6 cells per 1/2 yd2 in sections 9 and 8 respectively (Table 29). 125 TABLE 38: Ratio of CLB cells parasitized by I, julis to the total number of CLB pupal cells per 1/2 yd , determined from soil samples taken in early planted oat fields. Percent CLB cells parasitized % 100 Year Section 5 Section 8 Section 9 1969 NS NS .007* 1970 NS .002 .147 1971 .019 .009 .083 1972 .243 .053 .266 1973 .333 .350 .490 NS = not sampled *See text. 126 The total number of cells parasitized by I, luli§_in sections 5 and 8 (1.3 and 1.8) was similar; but, because CLB densities were greater in section 8, the proportion parasitized was much lower. In 1973, the proportion parasitized continued to increase, whereas CLB density con- tinued to decrease. The mortality attributed to different factors, including parasitism by I, julis, is shown in Table 39a and b where Table 39a shows the numbers per 1/2 ydz, and Table 39b the percent mortality attributed to each component. I, luli§_actually contributes twice to mortality because more than one generation may be produced during a season. The contribution to mortality attributed by the non- diapausing generation was estimated by counting cells with I, 13113. emergence holes, even though this estimate is difficult because some cells are broken during pupal sampling. In these oat fields, about 30% of the mortality caused by I, igli§_can be attributed to the non— diapausing component of the parasite population. The non-diapausing parasites continue to attack CLB larvae and contribute to the non- diapausing mortality. Soil sampling also revealed that Diaparsis sp. and Lemthagus curtus have been operating at a low but relatively con- sistent level. Density estimates (Table 39a) reveal that although the populations of these parasites have not increased as rapidly as I, 12113, relative mortality caused by these parasites has increased due to the decrease in CLB density. These two ichneumonids have been included together. Detection of these parasites by methods other than soil sampling has not been fruitful because densities have been too low to adequately monitor the populations at Gull Lake. Changes in total mortality caused by these ichneumonid parasites are shown in Table 39b. In 1973, the contribution of I, julis amounted to 74.5% of CLB pupal 127 TABLE 39a: Classification of CLB pupal mortality due to undetermined death and parasitism between 1970-1973 from oat fields in section 9 at Gull Lake. Density estimates are for 1/2 yd2 samples. I, julis D, carinifer Mean no. Dead Non- and Year cells CLB Diapausing Diapausing .L. curtus n 1970 97.315.7 l3.2:l.2 (6.81) 14.311.5 .03: . 30 1971 59.1i8.l 12.9:2.6 1.9: .5 4.9:1.0 .l i . 10 1972 31.614.0 3.5: .8 4.7: .7 9.5:2.0 .4 t 10 1973 5.1i .9 .1: .1 1.3: .3 2.5: .6 .4 i 14 TABLE 39b: Percent mortality % 100 due to each of the components from density estimates given in Table 39a. 31212 D, carinifer Dead Non- and Year CLB Diapausing Diapausing L, curtus Z M % T.j. 1970 .135 (.070) .147 .0003 .352 61.6 1971 .218 .032 .083 .0017 .335 34.3 1972 .111 .149 .301 .013 .574 78.4 1973 .020 .255 .490 .078 .843 88.4 () = estimated. 128 mortality or 88% of the total mortality for the combined effect of these components. Diaparsis sp. and A, curtus contributed 9.3% of the combined mortality. The distribution, density, and mortality attributed to these factors in 1973 are shown in Table 40a and 40b. Interaction of I, julis with A, flavipes. A, flavipes, a mymarid parasite of CLB eggs, was the first biotic agent brought to North America for the purpose of biological control of the CLB. Its establishment in the U.S. was reported by Maltby §t_§l, (1971). Early in this effOrt, Anderson and Paschke (1968) noted that the numbers of A, flavipes did not build up within a season until late in the CLB egg population. This observation was confirmed in Michigan by Morris and Moorehead (1971). Gage and Miller (unpublished m.s.) showed this to also be true in south- western Ontario in 1973. The significance of this delay in build-up, due to low overwintering densities of A, flavipes, and the subsequent rapid increase in parasitism of CLB eggs by A, flavipes at the end of the CLB egg population, has led to potential interaction between A, flavipes and I, iflliis This interaction is best illustrated by data collected from normal oats during the course of this study. The sequence of events, derived from population samples of CLB eggs, and the percent parasitism of CLB eggs by A, flavipes shows that egg parasitism builds up after peak egg density (Figure 29). The effectiveness of A, flavipes as a method for biological control of CLB populations is reduced due to this slow rate of increase during peak oviposition by CLB adults. The sub- stantial increase in parasitism by A, flavipes after peak CLB egg density indicates that this mymarid is removing CLB eggs and, subse- quently, larvae from the population within the same season. This 129 TABLE 40a: Classification of CLB pupal mortality due to undetermined death and parasitism in 1973 from oat fields in three sections at Gull Lake. yd2 samples per field. Density estimates are from 14-1/2 I, julis D. carinifer Mean no. Dead Non- —' and Section-Field cells CLB Diapausing Diapausing A, curtus 9- 9 1.29 0.0 .43 .64 0.0 9-13 5.29 .07 1.29 2.57 .43 9-15 7.71 .29 2.86 2.50 .57 9-25 6.79 .21 3.14 1.29 0.0 8- 7 8.00 .71 2.00 2.86 0.0 8- 9 1.93 .07 1.00 .36 0.0 8-11 2.71 .29 .93 .86 0.0 8-32 11.79 1.29 3.21 1.21 .07 8-34 3.64 .07 .24 .86 .07 5- 2 6.50 0.0 1.29 1.14 0.0 5—51 .86 .07 .36 .21 0.0 5-54 2.14 0.0 .57 1.14 0.0 5-59 2.00 .14 .57 .77 0.0 5-61 9.21 .07 .64 4.00 0.0 KRE* 6.80 .10 1.40 1.30 0.0 *A field 1/2 mile outside the boundary of the Kellogg Farm. TABLE 40b: 130 density estimates given in Table 40a. Percent mortality % 100 due to each of the components from D. carinifer Total Section- Dead Non- —' and Field CLB Diapausing Diapausing L, curtus Z M % T.j. 9- 9 0.0 .333 .496 0.0 .829 100 9-13 .013 .244 .486 .081 .824 88.6 9-15 .038 .371 .324 .056 .789 88.1 9-25 .031 .462 .190 0.0 .683 95.5 8- 7 .089 .125 .358 0.0 .572 84.4 8- 9 .036 .109 .187 0.0 .332 89.2 8-11 .107 .133 .317 0.0 .557 80.8 8-32 .109 .272 .103 .07 .554 67.7 8-34 .019 .236 .236 .07 .561 84.1 5- 2 0.0 .198 .175 0.0 .373 100 5-51 .081 .419 .390 0.0 .890 80.9 5-54 0.0 .266 .533 0.0 .799 100 5-59 .070 .285 .244 0.0 .530 99.8 5-61 .008 .069 .434 0.0 .511 98.4 KRE* .015 .206 .191 0.0 .412 96.4 *A field 1/2 mile outside the boundary of the Kellogg Farm. 131 100- O 1971 A “I60 -120 -eo -40 A % EL. 7 Z 2 I .. .1 I00' t) on 11- 1972 . v E N :3 ecv- ‘140 1— 5; 2 u” ‘9 a) “ 99 :2 60' ‘ 30 a) 1n _. (9 (2 (D D a: 40- -20 w 1'3 < m _ a 20’ 1 I0 -' t o (D '— < Z I E 2; ‘ n. a: 11.1 CL 10% C 1973 8C>- ‘ 4 6C>* ‘ 3 40- ‘2 20» . ' I . ..\\\\\\\\\\\\\\\\\\\\\\\\\\\ \. 0 200 400600 800 100012001400 DEGREE-DAYS (> 48°F) Fig. 29. The relationship between cereal leaf beetle egg density per ft and percent parasitism by A, flavipes. The hatched area is number of parasitized eggs per ft . 132 population reduction caused by A, flavipes is not likely to be signifi- cant as a mechanism for controlling damage caused by the CLB population because of the delay in population build-up by A, flavipes. The re— moval of eggs laid late in the season by A, flavipes will produce the effect of fewer late CLB larvae. This will not reduce damage signifi- cantly; but, because I, igli§_has a partial second generation which is not optimally synchronized with the CLB larval population (Figure 29), the removal of eggs laid late in the season reduces the potential number of hosts available to the searching second generation I, igli§_adults. Since it is largely the parasite's second generation progeny which enter diapause and serve as the source population of the fellowing spring, the removal of late larvae by A, flavipes reduces the numbers of I, luli§_which will be produced. This may have important consequences with respect to the numbers of CLB larvae parasitized during the first generation of I, jgli§_which is, at present, the most effective genera- tion for CLB population reduction. A, flavipes will undoubtedly reduce the response rate of I, juli§_to changes in CLB densities, and may also induce sufficient selection pressure against the second I, igli§_genera~ tion to eventually cause I, igli§_to have a single generation. Carl (1972) indicates that I, igli§_has only one generation in Switzerland, though in other European countries I, juli§_has two generations (Hodson 1929). It is unknown whether or not these differences in the number of I, igli§_generations are caused by pressure from A, flavipes, but it is important to investigate this possibility. DISCUSSION Some general management considerations. To place these quantita- tive descriptions of the interaction of parasites with the CLB in per- spective, it is useful to represent these interactions in a conceptual framework. Figure 30 shows an initial attempt by members of the CLB research group to depict these interactions and some of the important parameters associated with them. Not all of these interactions have been fully evaluated, but sufficient understanding of the system has begun to evolve such that management of the CLB on a regional basis can be initiated while results from these preliminary efforts are further evaluated. The dark arrows in Figure 30 indicate specific locations where man-induced management strategies are feasible. For example, within the I, igli§_component, control of overwintering parasite sur- vival depends on the degree of control over the disturbance of oat stubble prior to spring emergence. If stubble is plowed and disked, survival will be reduced significantly. The application of insecti- cides for control of CLB larvae feeding on the host plants will also determine whether or not I, igli§_will become an important factor in CLB management strategies. If CLB larvae are sprayed during peak parasitism, I, igli§_populations will be drastically reduced. In addition to representing the CLB ecosystem in block diagram (Figure 30), it is essential to develop a general conceptualization of the time domains when specific interactions are occurring. When 133 134 .mpcroa Fogucou vapcmpoa meow use mgmpwsmgma aurpmugos me_sau_eca 1.100.. .0551.“ _IIL.. a 3:93 “Oh—€014 . .53.“ I co..aEE:m H r3236 5:22.... G OS 5.2.5 2.3m H #0 <0 >2oclo ooh—’11. riot!“ 3.006 80 cud—w 2.1.3 Mn. cozovusk DA 0.0.3.693; _ b.3354. .I I_uotouozl Ann «I... .. (OZ-:30vem .1 Osa‘elfoh .P :10... .. . Empmxm mcwp mppmma mmmF megmu esp co covpmacmmmgame uwmemgum < an. 02% .‘O Du .auufila . . DD — z I > 3 =3: 2.... 4 design r!_32 mD=o~g<¢E .5994 5588 g .30 ZQPFvep co mgmnEDc ecu 302m memes nmsopm: .mw_:n 2H ucm mmmw>mFe am mwgcou use mmwuwmcmv Fm>em_ new mom mfipmmn eumF _mmemo mo mm>g=u Fmgmcww .Hm .mwu E om: m>85° F: Table 43), one can detect the importance of low rain and high heat in determining the low oat yield experienced in 1971. Although this analysis is not intended to be an explanation of the variability of oat yield, similar environmental parameters (rainfall and high temperatures during June) are important indicators of grain yield and CLB and I, igIIs mortality. The variability in levels of precipita- tion in Michigan for 10-day intervals during June for 1971 and 1972 is shown in Figure 38 (a-f). The increasing intensity of the overprint in Figure 38 indicates higher precipitation in each 10-day interval. Rainfall during mid-June best illustrates differences between 1971 and 1972 (Figure 38c and d). This technique helps lead to some understanding of the various factors that may unfbld within a season in a region, although there is little that can be done to manage rainfall or high temperatures that affect cr0p yield or CLB and I, quI§_mortality. However, these illustrations show that infbrmation derived from a detailed research program in a particular locality can provide some insight into what is occurring regionally. Of course, these extrapolations must be carefully examined. 153 TABLE 43: Total rainfall during May and June, 0085 during June at Gull Lake, and average oat yield (bu./acre) in Kalamazoo Co. from 1967 to 1972. Year June May + June May-June rain Kalamazoo Co. (°D ) Rain (in.) oD June (bu./acre) 85 85 1967 2 8.46 4.23 48.4 1968 3 9.84 3.28 55.0 1969 2 8.39 4.20 53.9 1970 3 7.10 2.36 48.0 1971 23 3.96 .17 32.9 1972 0 6.49 6.49 52.6 Ill.‘ 51.11. 154 |97| MAY 3| - JUNE 9, DAYS l5l-l60 MAY 30 - JUNE 8, I972 DAYS l5l-I6O JUNE 9 - JUNE IB, I972 DAYS I6I-l70 JUNE IO — JUNE I9, I97I DAYS I6I-I7O JUNE 20 - JUNE 29, |97I DAYS l7l-I80 JUNE I9 - JUNE 28, I972 DAYS I7l-l80 Fig. 38. Precipitation during ten-day intervals in June in 1971 and 1972. Darker areas represent increased amounts of rain. 155 One interesting feature was the cyclical nature of the CLB popu- lation measured in section 9 (Figure 23). I, iEli§.W35 obviously in- flicting significant mortality on the population at Gull Lake (Table 40a and b), but regional surveys (Haynes, personal communication, and Wilson, 1974) indicate that CLB densities have been declining. The parasite release program in Michigan began in 1971 and although re- coveries of I, jEAI§_were obtained in about 40% of the release sites after one year (Stehr, personal communication), parasites did not have sufficient time to initiate the regional CLB decline which was first detected in 1970. The CLB larval population densities measured in oats at Gull Lake are compared with a regional estimate of the CLB population measured from about 30 oat fields in Jackson County (Table 44). The trend is similar in both populations. At Gull Lake, attempts were made to provide optimal conditions for the CLB by providing side-by- side plantings of different aged crops. Another factor, which cannot be discounted, is the effect of pesticides on the population in Jackson County. Indications are that the CLB population is increasing again in Berrion County where the original infestation started (Webster, personal communication). From these indications it is not clear what role parasites will play in regulating CLB populations on a regional basis. If I, jEII§_builds up regionally as it has at Gull Lake, this parasite will obviously have an impact on the rate of build-up and decline of CLB p0pu1ations. The reasons for the present cycle are not yet clear, but Haynes (personal communication) has suggested that genetic changes in the CLB population could account for the cycle. 156 TABLE 44: A comparison of CLB larval population densities per ft2 at Gull Lake and in Jackson County. CLB larval incidence/ft2 Year Gull Lake Jackson Co.* 1967 19.4 11.8 1968 77.1 19.8 1969 197.9 115.6 1970 164.8 65.9 1971 58.8 16.2 1972 42.4 5.0 1973 3.6 5.7 *Peak larvae/sweep corrected to total incidence using §wo cor- rection equations: one to correct larvae/sweep to larvae ft , (y = .26 + 2.6x) and the second to correct peak larvae/ft to total incidence per season (y = 1.63 + 1.51x). 157 It is hoped that researchers will use information from this study to continue examining the role of I, 12113.1“ the population dynamics of the cereal leaf beetle on a regional basis, and to develop manage- ment plans to optimize natural enemies like I, julis. CONCLUSION This study has been an attempt to piece together some of the bio- logical phenomena that occur within and between two interacting insect species, a herbivore and one of its predators (parasites), within a three season interval in a limited area. There are drawbacks to limited area investigations because extrapolations to regional inferences about population behavior are often unwarranted. However, without detailed studies in some location, it is unlikely that realistic questions about host-parasite dynamics and regulation potentials could be asked, let alone answered, by regional surveys. One might argue that regulation would or would not occur whether or not such detailed studies were done. This may be true, but many of the observations were made around manipu- lation and this aspect of management must not be discounted. The par- ticular manipulations attempted, and the results, have helped in the understanding of CLB-I, ngI§_interaction and have also assisted in the guidance of the release program which resulted in considerable success, and may inevitably be a principle factor in the future reduction of CLB populations. One of the major limitations encountered was the lack of informa- tion about the biology of I, ngIg, Although some initial surveys and observations were done by Dysart g£_§I, (1973) on I, ngI§_in Europe, these observations were limited. Until this study little was known about seasonal dynamics, behavior, diapause, fecundity, mortality, etc., 158 159 of I, iEII§_or whether or not it could potentially regulate CLB numbers, even in a limited area. Fortunately, this study is not an isolated investigation, but an integral component of a project which also encompasses detailed, dynamic investigations of CLB adults, the host crop, and additional parasites as well as regional and international studies which will eventually be compiled as a model study of the understanding of an introduced pest. There are several points which warrant specific comment. Bio- logical investigations of the behavior of I, ngI§_should be continued. In particular, it would be useful to quantify attack by I, jEII§_females under field conditions and deve10p an attack model for this parasite. Diapause of I, ngIs was described but, because of conflicting informa- tion in Europe concerning the number of generations of I, igIIg, the proportion of I, ngI§_entering diapause through time should continue to be measured. There may be possible shifts in the diapause curve re- sulting from pressure from A, flavipes and other factors. Work should also continue on monitoring CLB and I, quI§_popula- tions at Gull Lake. The cyclical nature of the CLB population at Gull Lake indicates that the CLB species is dynamic, and specific experiments should be conducted to determine the cause of the changes in density when food is not limited. Several procedures_have been suggested for optimizing sampling of parasite populations and management of CLB populations with specific reference to I, ngI§_populations. This information was extrapolated from Gull Lake data to Michigan. Although the principles are sound, the suggested procedures should be carefully evaluated under field 160 conditions to test projected parasite population synchrony in order that sound management procedures may be put into practice. L ITERATURE CITED LITERATURE CITED Anonymous. 1972. Releases and recoveries of cereal leaf beetle larval parasites 1967 - 1971: a summary of releases and recoveries of imported parasites of Oulema melanopus (L.) indicating species, release and recovery sites and countries of origin. Animal and Plant Health Inspection Service, U.S.D.A. 16 p. Andersen, R. C. and J. D. Paschke. 1968. The biology and ecology of Anaphes flavipes (Hymenoptera: Mymaridae). an exotic egg parasite of the cereal leaf beetle. Ann. Entomol. Soc. Amer. 61: 1-5. Andersen, R. C. and J. D. Paschke. 1969. Additional observations on the biology of Anaphes flavipes (Hymenoptera: Mymaridae), with special reference to the effects of temperature and superparasitism on development. Ann. Entomol. Soc. Amer. 62: 1316—21. Barr, R. 0., K. Y. Lee, A. N. Kharkar and S. H. Cage. (in preparation). Formulation of a systems model for insect pest control--the cereal leaf beetle problem. Bejovic, P. 1967. Meigenia mutabilis Fall. (Diptera: Tachinidae) as a parasite of Oulema melanopa L. and its relation to Leptinotarsa decimlineata Say. Zast. Bilja. 18: 93-100. Boucek, Z. and R. P. Asken. 1968. Index of paleartic Eulophinae (excl. Tetrastichinae). In Index of entomaphagous insects. Le Francois, Paris. 254 p. Carl, K. P. 1968. Investigations on the cereal leaf beetle, Oulema melanopus (L.). Internal report. Commonwealth Institute of Biological Control, European Station, Delemont, Switzerland. 14 p. Carl, K. P. 1972. Investigations on the cereal leaf beetle, Oulema melanopus (L.). Internal report. Commonwealth Institute of Biological Control, European Station, Delemont, Switzerland. 20 p. Casagrande, R. A. and F. W. Stehr. 1973. Evaluating the effects of harvesting alfalfa on alfalfa weevil (Coleoptera: Curculionidae) and parasite populations in Michigan. Can. Entomol. 105: 119-28. Castro, T. R., R. F. Rupple and M. S. Gomulinski. 1965. Natural history of the cereal leaf beetle in Michigan. Michigan State Univ. Agr. Sta. Quart. Bull. 47: 623-53. 161 162 Clark, L. R. 1970. Analysis of pest situations through the life systems approach. In Concepts of pest management. Rabb, R. L. and F. E. Guthrie, eds. North Carolina State Univ., Raleigh, N. C. pp. 45-58. Clausen, C. P. 1956. Biological control of insect pests in the con- tinental United States. U.S. Dept. Agr. Tech. Bull. 1139. 151 p. Corbet, P. S. ed. 1971. Biological control programmes against insects and weeds in Canada: 1959-1968. Technical Comm. 4. Commonwealth Institute of Biological Control, Trinidad. 266 p. Debach, P. ed. 1964. Biological control of insect pests and weeds. Chapman and Hall, London. Debach, P. 1972. The use of imported natural enemies in insect pest management ecology. In Proceedings, Tall Timbers conference on ecological animal control by habitat management. No. 3. Tall Timbers Res. Sta., Tallahassee, Florida. pp. 211-33. Dysart, R. J., H. L. Maltby and M. H. Brunson. 1973. Larval parasites of Oulema melanopus (L.) in Europe and their colonization in the United States. Entomophaga. Finney, D. J. 1971. Probit analysis. Third edition, Cambridge Univ. Press, Cambridge. 333 p. Fulton, W. C. (in preparation). Computer mapping in entomology. Fulton, W. C. and D. L. Haynes. (in preparation). Summary of the data from the annual cereal leaf beetle survey 1967-1973. Gage, S. H. 1972. The cereal leaf beetle, Oulema melanopus (L.), and its interaction with two primary hosts: winter wheat and spring oats. M.S. Thesis, Michigan State Univ., East Lansing, Michigan. 105 p. Gage, S. H., R. O. Barr, P. C. Cota, D. L. Haynes, A. N. Kharkar, H. E. Koenig, K. Y. Lee, W. G. Ruesink and R. L. Tummala. 1972. Ecologically and economically compatible pest control. In Insect studies in population management. Geier, P. W., R. L. Clark, D. J. Anderson and H. A. Nix, eds. Ecol. Soc. Aust. (memoirs 1): Canberra. _pp. 241-64. Gage, S. H. and C. D. F. Miller. (in preparation). The occurrence and distribution of Anaphes flavipes (Foerster), an egg parasite of the cereal leaf beetle, in southwestern Ontario. Geier, P. W., L. R. Clark, D. J. Anderson and H. A. Nix. eds. 1973. Insects: studies in population management. Ecol. Soc. Aust. (memoirs 1): Canberra. 295 p. 163 Haynes, D. L. 1973. Population management of the cereal leaf beetle. In Insects: studies in population management. Geier, P. W., L. R. Clark, D. J. Anderson and H. A. Nix, eds. Ecol. Soc. Aust. (memoirs 1): Canberra. pp. 232-40. Haynes, D. L., R. K. Brandenburg and P. D. Fisher. 1973. Environ- mental monitoring network for pest management systems. Environ. Entomol. 2: 889-99. Hassell, M. P. and D. J. Rogers. 1972. Insect parasite responses in the deve10pment of population models. J. Animal Ecol. 41: 661-76. Helgesen, R. G. 1969. The within generation population dynamics of the cereal leaf beetle, Oulema melanopus (L.). PhD Thesis, Michigan State Univ., East Lansing, Michigan. Helgesen, R. G. and D. L. Haynes. 1969. The rotary flight trap in insect sampling. Proc. North Central Br., Entomol. Soc. Amer. 24: 20-1. Helgesen, R. G. and D. L. Haynes. 1972. Population dynamics of the cereal leaf beetle, Oulema melanopus (L.): a model for age specific mortality. Can. Entomol. 104: 797-814. Hilterhaus, V. 1965. Biologish - bkologische untersuchungen an blattafern der gattungen Lema und Gasteroidea (Chrysomelidae, Col.) (Ein beitrog zur agrarbkologie). (English Translation). 2. Agnew. Zool. 52: 257-95. Hodson, W. E. H. 1929. The bionomics of Lema melanopg L. (Criocirinae), in Great Britain. Bull. Entomol. Res. 20: 5-14. Huffaker, C. B. ed. 1971. Biological control. Plenum Press. 511 p. Huffaker, C. B. and C. E. Kennett. 1969. Some aspects of assessing efficiency of natural enemies. Can. Entomol. 101: 429-47. Juillet, J. A. 1964. Influence of weather on flight activity of parasitic hymenoptera. Can. J. Zool. 42: 1133-41. Lloyd, D. C. 1960. Significance of the type of host plant crop in successful biological control of insect pests. Nature. 187: 430-1. Lyubenov, I. 1956. Einfluss der dUngung und aussaatzeit auf die defallsstarke von Lema melanopa. Selskostoponska misl. 9: 37-48. Maltby, H. L., F. W. Stehr, R. C. Anderson, G. E. Moorehead, L. C. Barton and J. D. Paschke. 1971. Establishment in the United States of Anaphes flavipes (Foerster), an egg parasite of the cereal leaf beetle, Oulema melanopus (L.). J. Econ. Entomol. 64: 693-7. 164 Messenger, P. S. 1970. Bioclimatic inputs to biological control and pest management programs. In Concepts of pest management. Rabb, R. L. and F. E. Guthrie, eds. North Carolina State Univ., Raleigh, North Carolina. pp. 84-102. Miczulski, B. 1971. Studies regarding the bionomics, economic impor- tance and natural control affecting Oulema species in Poland. Agr. Univ. of Lublin, Project No. E21-ENT-l4. 51 p. Morris, A. P. and G. E. Moorehead. 1970. Angphes flavipes (Foerster) dispersion and population development in southwest Michigan, 1970. Proc. North Central Br., Entomol. Soc. Amer. 26: 41-6. Morris, R. F. and W. C. Fulton. 1970. Models for the deve10pment and survival of Hyphantria cunea in relation to temperature and humidity. Mem. Entomol. Soc. Can. 70. 60 p. Pimentel, D. 1963. Introducing parasites and predators to control native pests. Can. Entomol. 95: 785-92. Rabb, R. L. 1970. Introduction to the conference. In Concepts of pgst management. Rabb, R. L. and F. E. Guthrie, eds. North Carolina State Univ., Raleigh, North Carolina. pp. 1-5. Royama, T. 1971. A comparative study of models for predation and parasitism. Res. Pop. Ecol., Supp. 1. 91 p. Ruesink, W. G. 1972. The integration of adult survival and dispersal into a mathematical model fer the abundance of the cereal leaf beetle, Oulema melanopus (L.). PhD Thesis, Michigan State Univ., East Lansing, Michigan. Ruesink, W. G. and D. L. Haynes. 1973. Sweepnet sampling for the cereal leaf beetle, Oulema melanopus. Environ. Entomol. 2:161-72. Ruesink, W. G. and D. L. Haynes. (in preparation). A model for the abundance and dispersal of the cereal leaf beetle, Oulema melangpus (L.). Sailer, R. I. 1972. Concepts, principles and potentials of biological control by parasites and predators. Proc. North Central Br., Entomol. Soc. Amer. pp. 35-9. Saunders, D. S. 1964. Diapause of maternal origin. Proc. 12th Int. Cong. Entomol., London. 182 p. Simmonds, F. J. 1946. A factor affecting diapause in Hymenopterous (parasites. Bull. Entomol. Res. 37: 95-7. Smith, R. F. 1970. Pesticides: Their use and limitations in pest management. In Concepts of pest manggement. Rabb, R. L. and F. E. Guthrie, eds. North Carolina State Univ., Raleigh, North Carolina. pp. 71-83. 165 Southwood, T. R. E. 1966. Ecological methods with particular reference to the study of insect p0pu1ations. Metheun and Co., London. 391 p. Southwood, T. R. E. and M. J. Way. 1970. Ecological background to pest management. In Concepts of pest management. Rabb, R. L. and F. E. Guthrie, eds. North Carolina State Univ., Raleigh, North Carolina. pp. 6-29. Stehr, F. W. 1970. Establishment in the United States of Tetrastichus julis, a larval parasite of the cereal leaf beetle. J. Econ. Entomol. 63: 1968-9. Stehr, F. W. 1972. Assessing the potential of the biological control component of a pest management system, with a brief review of the philosophy involved. Proc. North Central Br., Entomol. Soc. Amer. pp. 47-53. Stehr, F. W. and D. L. Haynes. 1971. The establishment in the United States of Diaparsis carinifer, a larval parasite of the cereal leaf beetle. J. Econ. Entomol. 65: 405-7. Stehr, F. W., P. S. Gage, T. L. Burger and V. E. Montgomery. (in preparation). The establishment in the United States of Lemophagus curtus, a larval parasite of the cereal leaf beetle. Stern, V. M., R. F. Smith, R. Van den Bosch and K. S. Hagen. 1959. The intigrated control concept. Hilgardia. 29: 81-154. Tummala, R. L., W. G. Ruesink and D. L. Haynes. (in preparation). A discrete component approach to the management of the cereal leaf beetle ecosystem. Turnbull, A. L. and D. A. Chant. 1961. The practice and theory of biological control of insects in Canada. Can. J. Zool. 39: 697-753. Varley, G. C. 1970. The need for life tables for parasites and predators. In Concepts of pest manggement. Rabb, R. L. and F. E. Guthrie, eds. North Carolina State Univ., Raleigh, North Carolina. pp. 59-70. Venturi, F. 1942. La Lema melanopa L. (Coleoptera, Chrysomelidae). Redia. 28: 11-88. Woods, C., A. Budge, E. Kenyon, Y. Frohm and K. Turnbull. 1972. Michigan county statistics: field crops 1959-1972. Michigan Dept. of Agr., CrOp reporting service, Lansing, Michigan. 109 p. Wellso, S. C., J. A. Webster and R. F. Rupple. 1970. A selected bibliography of the cereal leaf beetle, Oulema melanopus (Coleoptera: Chrysomelidae). Bull. Entomol. Soc. Amer. 16: 85-8. 166 Wilson, M. C. (in preparation). 1973 Report of infestation of oats by the cereal leaf beetle. Purdue Univ. Agr. Exp. Sta., Lafayette, Indiana. APPENDICES Oven dry wt. Wet weight .3 16 tillers No. i29.| Total larvae 0.0 Instar IV 0.0 0.0 0.0 I.iixO3 0.0 0.0 0.0 Instar T-WHEAT (E) R-WHEAT (E) Instar 0.0 l .3 .3 .li..I .2+ .2 Instar 0.0 .91 .71 .E NI‘OONINN'I Eggs Density per ft.2 of cereal leaf beetle life stages in wheat with associated crop biomass information (I97I). Lyn? DD48 I64 235 332 422 49I 660 793 976 Appendix I Date 5/ 4 S/ll 5/I8 5/25 6/ l 6/ 9 6/l5 6/22 167 —-n 13% 225.01I3.2 48.7 0 I02.9+7.7 0.0 00 OO 00 OO COO 000 i. .i |2.6i2.6 I64 235 332 5/ 4 S/il 5/I8 o~—--——-~i fiflfififl U\W\ -—- c: (1040\u3a) G)()P~P~¢) o1m>-—ouc> 0\o~mx—-m> +i+I+I+I+I G)O\F\P~a) a><»w1-o1 U\P~()C>O\ 04040101- o~o~uxc> - Q- a C 0v HDDQH «\m\—-—-c> m)u1r~n1—- a1e~e~m>m> ()G)¢)F\C) c: C) +IH - -—<> c>c> --:c> c>c>gj44c> C) (3 ~ +Ifi +I- c>—-v1—-c> 04F) c>c>c> +'-H - o o m1e-c>c>c> r~c>cvcv C) + I 63440 <-a> oa—-c>~i¢> oao~m>o~n~ VVOI‘O K\—-O\U\OJ o1 —-oa \\\\~\\\\\ 1n\0\o\0\o B-WHEAT (E) “500N000 _ N (\m “Dnfififiuu ODOh'flVNV I" NNI‘CDQ N “WI-“NB 3| 34 4 vnmmom—m ()GJCJOJN\¢JC)OJ ._ m... HHHHHHHH - ovvm QOVM—NO— —VV\ON\OOU\ —-—-—-o¢o¢—-oe- h-fi’P-OJ—-F~¢)P~ Lntnmom vv HHHHHmHH h @500 MONIOOHV— mVO‘I‘C’ONOO‘O ooovv——o oo o c>c>c3c3 o ..'+l+‘+l. c>c>c>c>—-—-—- c>c>c>c>-:c> -<> <3¢3<3<3 +h3£§k3 00000000 00000000 04— V O i i. i 0.0 I‘VO‘OQMM - c: + + - 04403000 Q’U\9404—-C>N\() m>ririouosm>oah~ —-0¢F\fl’fl’¢)h~o\ <~-—a1ux-—¢>1noo om * P~N1c><-n1riwi mnN—— H H++ 440a " hmomm mm— NN—omov nmooono MQVOFO— mm—mmmo -—N --NN \\\\\\\ mm©\0\0\0\0 R-OATS (E) I 4 8 W3 %. Ni o1ou~i ° +l:)+l+l+l:) Nioxm>m>—- o~m>o~—-c> v-wxm1m1mx 34.0:3.8 4I.9 0.0 .8 26.3:3.2 I3.QLI.9 2.5+ 0.0 i \ommmv O NN— - +I+|+l+l+l OO‘IDV’VLD 0.0 -—MV\O —-n:c>«1r:—- 440344 O'tOBN N 0.0 “(ONO—fin MNVO’IIOM "garage [‘00 24I 4|.9 332 I5l. 422 I33. 49I 0. 660 793 976 5/i2 5/I8 5/25 6/ I 6/ 9 6/15 6/22 B-OATS (E) -NVIOOO +I+|+I+l+l+l (DOVOV— Nth—VOL“ N LON—0mm N?Q\OI‘ + +l + +I+ mlmgdnd “\VVI’IMO N'GINQO vw—cncuoeaa (\IIMNNN— + +I+I+I+I+l NlfiV—FO MMflO‘O‘O NVV'MNM r~-c> o — - + + c>c>c>wdéioJ «Susq- -l.nNQ OO -- . - +I+i+l+l OOH—0") CDVN —mm—1n -+I+I+I+I+I c3— (DON—m— “VON—- wwyuug GSQMZ6N 332 422 49I 660 793 976 S/IB 5/25 6/ I 6/ 9 6/I5 6/22 (n=I5) + S.E. b< Grass wet weight Crop wet weight Total larvae IV Instar Instar Instar WHEAT (A) Instar Density per ft2 of cereal leaf beetle life stages in wheat with associated crop biomass information (I972). Eggs (grass) Eggs (crop) Appendix III 0048 Date 1639 K)P~-C)OJ N\0\—-M\—-<-oarx —-—-oivwnxnin-—vn ——_—— N _— +l+l+l+l+l+ + +l +I+l+l+l+l+| l+l+l EIEIEIEIE) C)U\<3P~P~-J:}C) —-v~mxc>—-V\33a)—. 01010404 fi'flWO\0(D wxv-M\h-v-h~M\- —-w\a>N\-c><~vin K\O\N\—-- NNOJO\V\01—-OJOJ -N\w\vwnu§c5r:c> v w\I)C>C)Odu;st o:m:rx<~c>a>h~c>r~ «>N\a)a>K] <>m>m>a)0\a)a)a) -—Io\oc>—-<-V\a) c>c>m>vxa3uxa3oa C>c>V\—wnrn<3c> oa c>c> —-o¢—-—- C):>—-C>C>C> P~ c>c>c>c>m>v--—- C>C> ~1Lnrnljrq-j _ N —NMN— OOONMV’NNO OOO ‘ ' 000.. c on no. on o o I+Io+' no 0+I+J+I .f' o ooH-H+'+|+|o c>c>c>- «x c>c>c>—-h-h- —- C>c>c>vwnl\tnrn<3 (D U c3c>c>__ -. :2 c>c>-N‘F‘N‘.-c> E; C>-—-N\ c>c>ux<>w\—-V\c> C>C>-:K>V\O:-:-:C> O _—n —'°J_-F‘ c: -'_'—'c>—' c)c) c>-c>-c>c>c>c>c> o o o o o o o '0 o o H+lcfl+lo o “H“.H... o+|o o. o O. _n O _._._o._ooo O O—OOOOO * “”‘“N” ”000*” 9%? .N i 00 —— 00 + + + + + + + - . +l+l+l+l+l+l- --H «ISI_JGIJqu OJUJ-thgigiCDC) "2"}OIW3 .U)C>C>-: _._._. _. ° '_1 ' nI—-—-w\u\ v-w\r\ 04- :n\0\0\om>m>c>—-—-C) WxK)()K)C>-—-C)U\ O\P~P~fl‘h-O\ O‘P‘P‘v'h-O\C)F\ O‘P~vat\h-0waoIq) C>F~OJW\OI¢)<‘- C>P~°4W\“J¢><”—‘D (:QQ\\ :“QN “Q (:QQ\\oI—-c>0I —-—Nf’\u‘\-- +I Cassia F\V’h~V’d)—- F\ w\-c> a) —- F\ V l\ V — N (V-—ln O - + <3 Iflifl In O LhMO - + c; MJJIéI N (I) u\ 0\oq- a! :Idiéi —- UN (0 O —M\O +l +l+|+ ox —-h~h— N i\ N m - c: c: +| o o «I c: C) O‘lnl‘rfinfi v- (V -— +I+l+l+l +| —-—-0\c> ux 04r~—--— \o v- (V I I I I I I I I I I I I 23<323<322<3 (0 c3 —- V f‘ 0‘ v- In Io Ln (V cm N \\ \\ ‘\ uw \0 I0 .3i..2 lf70 ox U\ a) 04 + x A d J —— — u" N u>w\m><-h--a30\ NQMOU’NNMQ + dfifiid£fi_ <--b~h-—-h~oIv- -0\—-N\cvcu-Io a) h— ox C) F\ - c: u) NI--—- - c: + H - Ii .J..:I c, CD _ NO NO 0 34A +l-«H - c> NIC:~\ c: m um ._ _ c: C) + +I- - Rd c,:5 c: _m _ ._ c: C) H +l- - _# .03 o C) c: C) C) c3 c3 c3 c: _m m __ c3 c: C) .+ .+| . ii$Ic>ch>vw c: I I l I I I I I I I I I I I I I :3<3:z<3:z<3:z<3 —- C) U\ a) C) F\ 04 Ex «I ox c> —- v- - a) U\ - pa ow \\ \\ \\ ~\ Io Io I0 I\ OATS (B) —nvvv:~\o—n I43.9iJ9.0 245.6:J5.8 236.6:J8.8 263.0:29.I O I 4.8 9 5 3 9 9 8 OOO OOOUNCDO‘ OONMVQMN— +lfl +l+l+l+l+l OOUWBO‘O‘I‘NM —-N _- VMNONVN +I+I+I+Igd‘flyfl OO 0\ 0‘0 In N——- _n-——— +l+liI+i+l+lo +l: NBBVVVONIN -— N — _ + + +| + + + AADmeaag O‘CDOO‘IAO—‘ON _n—-- oooo——omeo BFVNOBMNm NN'IVIDO O‘C— thva—mm —-NN -NN \\\\\\\\\ LnLnln\O\O\O‘O\Ol\ 7 25.7i5.2 O 9.7 i. 3|.7i] 40.5 l77.9:24.7 l32.9:24.7 l83.6¢20.3 '05 l.3+ I.0:..5 I.IZ.4 .7:.I .03-+04 OATS (C) .5 l.8+ l5) (n 930 I025 I|58 6/28 7/ 5 6/2l * ‘X'+ S.E. 171 Aomucv .m.m + x * ma “Nam: fimmofim «.313 _. .13. one 3A8. o.o 0.0 _3 _NE N.m.Hm.om_ o._+_.mn _.NHB._m _. _:H_. no.+no. o.o pwo o.o w_o m_\o n.__Hm.omN WANT: n._HN.mn m._ _..«¢. .13. N.Hm. _.H_. moMmo. m: NCO o.o.Ho.mo_ m._+m.ov m._mwxoo o. mozflmo. _eHN. _.mw. _.+_. _.+N. _vo n \o _.o.Hm.m__ o._+N._m v. 0.0 0.0 no.+no. _sz. n2“... mov _m\m v.v.Hm._o m..Hm.Nm no. 0.0 0.0 0.0 neaflmo. Na“... oov mm\m on F.nm o.NH;.oo_ _. mOaHmo. mezflmo. meaHmo. 0.0 0.0 n_o m_\o o.v_.flo.mnm m.NHv.ov m._Ho.mo_ N._ THN. NIflm. N.Mm. _.H_. 0.0 m: NCO _.n_Mm._mN 0.30.3 o. 0.0 THN. _.+m. .53. TH? 30 K. \o m.m_+m.mom v.:flo.cn _. 0.0 0.0 0.0 _afl_. N.+o. mac _m\m 0.0 H6.mm_ N.fiHo.mv no. 0.0 0.0 0.0 mo.Afio. NzHN._ oov mm\m n.m_ud.m__ 0.0 0.0 0.0 0.0 0.0 *mzfin. new o_\m “mo FLm_ >_ Lm+mc_ ___ Lm+mc_ __ Lm+mc_ _ Lm+mc_ mmmm mvoo o+mo +cm_d _m+0F .Amno_v co_+mEL0+c_ mmmeo_n coco um+m_o0mmm c+_3 +mocz c. mmmm+m o$__ o_+ooo +mm_ _mocoo +0 N++ Lou >+_mcoo u> ancmaa< 172 Aonncv .w.m.u.m . m.a.Hm.om_ o.MMm.mv N.fifla.oa 0.0 0.0 0.0 0.0 0.0 0.0 nav. N_\a m.m.fla.no_ m.m+o.mv n.<fia._o 0.0 0.0 0.0 0.0 0.0 N:#m. Nam. m \n n.w.Ho.v__ a.NH¢.hn N.fifl..mv _. _2H_. 0.0 0.0 neaflmo. msfla. a___ aN\o m.m_uN.no m.N\© m.ofiMw._m_ a.eHo.av _.NHv.av a. _afim. _aHm. _Ifl_. moaflmo. Nzflo. .aa _N\o N.o_+m.om_ v.qum.om m.fiHm.a¢ o.N Nafim. Njfla. mafia. _IHN. NIH... n_a m_\o o.m2fim._a m.NHv.nm o.fiwm.vm m.m moaflmo. waflm. Njflm._ _zflv. ozflv.n man N_\o 5v No.3 m._HN.om a. Hmém a. 0.0 noflmo. _.Hm. N13. mefi :E a \c 0.. .«a.NN m. Mma. _. 0.0 0.0 0.0 _.H_. m.+m.N mac _m\m o. .Ha.a v. +v.m_ no. 0.0 0.0 0.0 noaHmo. NaHm. woe nm\m v. .Hv.~ 0.0 0.0 0.0 0.0 0.0 *_au_. hem o_\m Amy mkcm_ >_ Lm+mc_ .__ Lm+mc_ __ Lm+mc_ Lm+mc_ maam mvoo o+mo +cm_a _m+o» .Amwa_v co_+mEL0+c_ mmmeo_n aoLo oo+m_00mmm c+_3 m+mo c. moam+m o+__ m_+moa cam. _mocoo +0 N+$ Log >+_mcmo HH> ancmaa< l‘IICHIGQN STATE UNIV LIBRRRIE 93llll lllll loll I III III