v- .nj':f- 1s? L“ '1; 3; qfiaL ifs-5L -{. ‘ “a I :‘v' ‘5‘! “ ~r~f.? -‘:.- ._ I 'x't' 13:? 1 W: was. ,v ._ w.” 4 ‘f‘r‘..~;-—-v_ _ 3:71; I9“ w“ 3.11%» . 5w- 5': ‘} mg? 5 r o.;'.‘ pr - V”: o- s - . c. t“ m -a f‘ ’5‘; ' a ” LlJERARy-l Will/ill”!!! lIll/ll!!!Ill/Illll.’!//.«'IL’I/l/H/I/l/U/llill “£47 gran Sn: 3 1293 10388 9642 - . '3 . a [r ‘ - :‘C- .1 b. . . " . t. - ...t.7 .4‘ s5 -. ‘03.”. THE-:3-.. This is to certify that the thesis entitled BIOLOGY OF ILLINOIA PEPPERI (MACGJ), THE BLUEBERRY APHID, AND ITS RELATION TO BLUEBERRY SHOESTRING VIRUS DISEASE IN WESTERN MICHIGAN presented by Erwin A. Elsner i has been accepted towards fulfillrnent of the requirements for Masters degreein Entomology A ”AL 2". M; a... / Major professor Date 12 February 1982 0-7639 MSU LIBRARIES RETURNING MATERIALS: P1ace in book drop to remove this checkout from your record. FINES W111 be charged if book is returned after the date stamped below. Bra-0.534197% MWB 1 i I a...— . FEBIQflOZEQUé '2 BIOLOGY OF ILLINOIA PEPPERI (MACG.), THE BLUEBERRY APHIB, AND ITS REEATION TO BLUEBERRY SHOESTRING VIRUS DISEASE IN WESTERN MICHIGAN By Erwin Albert Elsner A THESIS Submitted to Michigan State University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE Department of Entomology 1982 ABSTRACT BIOLOGY OF ILLINOIA PEPPERI (MACG.), THE BLUEBERRY APHID, AND ITS RELATION TO BLUEBERRY SHOESTRING VIRUS DISEASE IN WESTERN MICHIGAN By Erwin A. Elsner The biology of IllinOia pepperi (MacGillivray) on cultivated highbush blueberry (Vaccinium corymbosum Linn.) in Michigan is examined. This aphid is a vector of Blueberry Shoestring Virus (BBSSV) disease, and its relation to this disease in Western Michigan is studied. An analysis of disease control economics is included. Symptomatology and details of the occurrance and spread of BBSSV within blueberry plantings are given. Field biological studies on I. pepperi include an analysis of yellow pan trap catches of alatae, aphid life cycle and seasonal history, and a brief discussion of the predators, parasitoids and other mortality agents of this aphid. The results of a 3 year search for alternate host plants for I. pepperi in.Michigan are given. The development of an optimal sampling scheme for aphid density estimation is outlined and the results presented. Results of laboratory experiments to determine the lower developmental threshold temperature, developmental rate, generation time and fecundity of apterous viviparous I. pepperi are presented and discussed. Dedicated to my parents in appreciation for their 25 years of dedication to me. ii ACKNOWLEDGEMENTS I wish to thank Dr. Mark Whalon, my graduate advisor, for giving me the chance to work on this project; he guided my efforts, saved me from pitfalls and gave the necessary pushes when I slowed down. I thank the members of my graduate committee, Drs. Jim Miller, Frederick Stehr and Donald Ramsdell for their ample support, openness to opinions and ideas, and their swift review of this manuscript. I deeply appreciated the support of the Michigan Blueberry Growers Association, Grand Junction, MI. Their financial assistance made this project possible, and their administrators, employees and member growers helped carry it to completion. Their Director of Research, John Nelson, provided a great deal of information to me and often assisted with field projects, along with their field scouts, George Jaeger and Harold Huizenga. Member growers were extremely cooperative. Terry Davis gave me many days of field assistance on every part of this project, rain or shine. His help with Laboratory experiments made it possible for me to get away when I needed a break. iii The department of Entomology Graphics Laboratory produced many of the figures in this work. My special thanks to Lana Tackett for the excellent aphid illustrations. I thank Kerry Hulliberger for her fine typing service in the preparation of this manuscript. iv TABLE OF CONTENTS INTRODUCTION ............................................ l ECONOMIC JUSTIFICATION .................................. l3 BLUEBERRY SHOESTRING VIRUS DISEASE ...................... 22 OCCURRANCE AND DISTRIBUTION OF - BBSSV IN OTTAWA CO., MI .............................. 26 SEASONAL HISTORY OF ILLINOIA PEPPERI ON HIGHBUSH BLUEBERRYTTTT ............................ 34 ALTERNATE HOST SURVEY ................................... 62 OPTIMUM SAMPLE DETERMINATION .......... ' .................. 67 LABORATORY STUDIES ...................................... 76 GENERAL DISCUSSION ...................................... 93 APPENDIX 1: RECORD OF DEPOSITION OF VOUCHER SPECIMENS .................................... 97 APPENDIX 2: FIELD LOCATIONS AND LAYOUTS ................. 101 APPENDIX 3: 1979 PAN TRAP DATA AND WEATHER INFORMATION .......................................... 106 BIBLIOGRAPHY ..................................... w ....... 122 10. 11. 12. LIST OF TABLES Percent of commercial blueberry plantations infested with Illinoia e eri and Ericaphis scammelli from I96I-I96E EEiIes 1966) .............. 10 Crop utilization and average market prices for Michigan blueberries ........................... 14 Highbush blueberry production costs. 1981 estimates (after Kelsey 1979) ...................... 16 Approximate costs per acre for a removal- replant operation as a solution to BBSSV disease in Michigan, 1981 .......................... 20 Tests of Blueberry Shoestring Virus trans- mission by Illinoia eri (Ramsdell, unpublished data I97 ............................. 24 Differences in BBSSV symptom expression on north and south sides of blueberry bushes. July 23, 1979 ...................................... 28 1979 BBSSV Survey results: number of bushes with visual symptoms on June 28 and August 8 ....... 28 Dates of first and last captured alate Illinoia e eri in yellow pan traps in western MicEigan, 1979-1980 ........................ 39 Directional analysis of alate Illinoia pepperi caught in yellow pan traps in blueEerry plantings Ottawa CO., MI., 1979 .............................. 43 Predator and parasitoid families attacking Illinoia pepperi in Michigan 1979—1981 ............. 57 Populations of Illinoia pepperi on caged and uncaged blueberry bushes, Ottawa CO., MI. Counts made on August 8, 1980 ...................... 60 Observations of Illinoia pepperi on alternate host plants in Ottawa CO., MI. (1979-1981) ................................... 64 vi 13. 14. 15. l6. l7. 18. 19. 20. 21. 22. Actual density counts of Illinoia pepperi on blueberry ('Jersey' cultivar? in Ottawa CO., MI. All counts made on August 30,1979 ........ 69 Actual densities, average densities, sample means and averaged sample means of Illinoia e eri on 'Jersey' cultivar blueberry. Data are arranged by ascending order of actual densities and grouped into levels ........... 70 Regression equations and related statistics for each sample type tested in 1979 ................ 71 20 leaf sample means, predicted densities and actual counts of Illinoia pepperi, August 12-15, 1980 ................................. 74 Mean days per developmental stage of Illinoia pepperi on excised leaf discs at six treatment temperatures (l6L:8D photoperiod) ............................... 79 Regression statistics for Illinoia e eri developmental rate studies in controIIed environment chambers, 1980-1981 .................... 80 Mean degree days (base 3.40C) per developmental stage of Illinoia pepperi on excised leaf discs at six treatment temperatures (l6L:8D photoperiod) .................. 81 Mean ages and mean degree days (base 3.40C) for molt to adult stage, generation time, and age of death of Illinoia pepperi on excised leaf discs...............f ................. 82 Fecundity of apterous viviparous Illinoia pepperi at six treatment temperatures on exc13e blueberry leaf discs with a 16L:8D photoperiod ................................. 86 1979 pan trap catches of alate Illinoia e eri and associated weather statistics EieId #393 ......................................... 107 23. 24. 25. 1979 Pan trap catches of Alate Illinoia pepperi and assoicated weather statistics. Field #7 .............................. 111 1979 Pan trap catches of Alate Illinoia e eri and associated weather statistics. Field #54A ............................. 114 1979 Pan trap catches of Alate Illinoia e eri and associated weather statistics. Field #281 ............................ 118 viii LIST OF FIGURES Life cycle of Illinoia maxima (Mason) on Rubus parviflorus (Gilbert and Gutierrez I973) .................................... 9 Geographical distribution of blueberry infesting aphids in southern Michigan (Giles 1966) ....................................... 11 Observed [*] and extrapolated [I] plants with visual symptoms of Blueberry Shoestring Virus disease in Michigan from 1957-1985 (Ramsdell et. a1. 1980). Y = number of infected plants; X = year .......................... 18 Sections of two computer generated BBSSV infection maps from 1979 survey, Ottawa CO., MI ............................................ 30 Samples of pan trap material for 1979 and 1980 ..... 36 Alate Illinoia e eri caught in yellow pan traps In Ottawa CO., MI, 1979. Arrows indicate the dates of significant rainfalls and pesticide applications ......................... 41 Alate Illinoia e eri caught in yellow pan traps In Ottawa CO., MI, 1980. Arrows indicate the dates of significant rainfalls and pesticide applications ......................... 42 Life cycle of Illinoia pepperi (MacG.) on highbush blueberry (VacEInium corymbosum) in Michigan ........................................ 47 Common morphological forms of Illinoia pepperi: (A) green viviparous apterae; (B) green viviparous alate; (C) red viviparous apterate ...... 49 Oviparous female and eggs of Illinoia pepperi found on December 5, 1981, Ottawa CO., .......... 55 ix 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. Plots of observed (actual) density vs. average sample means for four sample types used for estimating densities of Illinoia pepperi on mature highbush blueberry ersey' cultivar). Ottawa CO., MI, 1979 ......... Relationship between developmental rate (instars/day) and treatment temperature for Illinoia pepperi on excised leaf discs ....... Relationship of degree days per developmental period to temperature for Illinoia pepperi on excised leaf discs. Bars represent i I standard deviation about the means ................ Relationship of adult pre-reproductive period and generation time in degree days to temperature for Illinoia pepperi on excised leaf discs. Bars represent i,1 73 ..79 .84 standard deviation about the means ................. 85 Fecundity of apterous viviparous Illinoia pepperi on excised blueberry leaf dIscs at three temperatures ............................. Mean degree days per stage of Illinoia pepperi on exSised leafodiscs. Tgeatment tgmperatures: (1) 5 8; (2) 10 8; (3) 17 C; (4) 23 C; .87 (5) 26 C; (6) 29 C ................................. 90 Apterous viviparous (A) and alate viviparous (B) forms of Illinoia pepperi (MacG.). Approximately 20X .................................. 94 Map of southern Michigan showing locations of principle study fields .......................... 101 Field #393, Park Township, Ottawa CO., MI, wesley Waldron, owner .............................. 102 Field #7, Port Sheldon Township, Ottawa CO., MI, Allen Devries, owner ........................... 103 Fields #54A and B, Olive Township, Ottawa CO., MI, Vern Brower, owner ............................. 104 Field #281, Polkton Township, Ottawa CO., MI. Frank VenRoy, owner ................................ 105 INTRODUCTION The blueberry aphid, Illinoia (3 Masonaphis) pepperi (MacGillivray) can be found in most areas in which highbush blueberry (Vaccinium corymbosum Linn.) is grown in Michigan. It was a suspected vector of Blueberry Shoestring Virus (BBSSV) disease for many yearsl, but not until 1979 was there substantial evidence for the association of I. pepperi and the spread of BBSSV (Ramsdell 1980a). In recent years, much attention has been directed toward the control of this aphid. BBSSV disease causes extensive economic loss to highbush blueberry plantings by the slow decline and eventual death of infected bushes. Berry production drops dramatically within a few years of the onset of symptoms. This reduction in productivity plus the even- tual stand decrease (from removing bushes) was estimated to cause a $16,000,000 dollar loss to the blueberry growers and the associated industry (Ramsdell et. a1. 1980) in the United States. 1J. Nelson, Director of Research, Michigan Blueberry Growers Association, Grand Junction, Mi. Personal Communication, 1979. Systematics of Illinoia (= Masonaphis) pepperi (MacGillivray) The Classification of the group of aphids to which 1. pepperi belongs has been revised many times in efforts to clear confusion due to synonomy. ‘Wilson (1910) divided the subfamily Aphidinae into three tribes, the Trichosiphini, Aphidini and Macrosiphini. He erected the genus Illinoia in the Macrosiphini based partly on the length of cornicles. The genera Amphorophora, Macrosiphum, and Myzus were also placed in this tribe. Hille Ris Lambers (1939) while discussing Macrosiphum, writes: "This genus (Illinoia) of Wilson was meant for those species of Macrosiphum. . . which have the cauda without a Basal constriction. In this sense the genus Illinoia is senseless, because the closest aIIIed species may show difference in this regard. . . and variation ‘within species is quite common." He then identified Illinoia on the basis of the complete absense of rhinaria on the 3rd antennal segment of apterous viviparous forms of this group. In this same study the genus Masonaphis was erected based on the type species Illinoia rhododendri Wilson, an European species found on Ericaceae. The genus possesses rhinaria on the 3rd antennal segment, distinct reticulation of the apex of the cornicles and 5 hairs on the lst tarsal joint. The last two characters separated Masonaphis from Amphorophora. He then placed Amphorophora azaleae, A, borealis, A, rhododendronia and A, vaccinii in the genus Masonaphis, and suggested that these were likely all synonyms of A, rhododendri. MacGillivray (1958) arranged the genus Masonaphis2 into four morphologically and biologically homogeneous subgenera; Masonaphis "sensu stricto" containing species on Ericaceae; Oestlundia containing species from.Rubus, Amphorinophora containing species associated with Lonicera and the subgenus Ericobium which was associated mainly ‘with the compositae and Ericaceae. Masonaphis pepperi was then described as a new species in the subgenus Ericobium. Her key to this subgenus uses many difficult and variable characters. Relative lengths, pigmentation (difficult with cleared and slide mounted specimens), number of tarsal hairs (admitted to be quite variable in the same work) and whether or not certain tubercles are conspicuous. Many judgements must be made to key a specimen. To add to the problem, she.states: "Mention should be made to the very frequent occurrence in this subgenus of apterous viviparous morphs that in their higher number of rhinaria and presence of vestigial occeli resemble alatae; such alatiform apterae occur simultaneously with normal apterae viviparae." Five morphological forms of M. pepperi were described; an apterous fundatrix, an apterous viviparous female, 2She considered aphids of the "Amphorophora group" with swollen and reticulated cornicles to be in the genus Masonaphis. an alate viviparous female, an apterous oviparous female, and an alate male which she doubted was of the same species (MacGillivray 1958). The nature of the key characters and the frequent morphological variation may be the cause of the taxonomic difficulties experienced with the determination of aphids samples taken in recent years (see page 5 for discussion). Smith and Parron (1978) stated that the genus Masonaphis was synonymous with Illinoia thus placing pepperi in Illinoia since it was the first of the two genera to be established. No mention was made concerning the morphological characters that were originally used to separate the genera, such as the rhinaria of the IIIrd antennal segment (present in Masonaphis, none in Illinoia as originally described). The reason for this change of classification was not given. Historically, the aphids found on cultivated highbush blueberry in Michigan have been determined as l, pepperi. Aphids collected from blueberry near Fennville, Michigan in 1964 were determined to be l. azaleae3. Surveys in the mid-1960's made by Giles (1966) reported A, pepperi and Myzus scammelli colonizing highbush blueberry. Specimens 3J. Nelson, Director of Research, Michigan Blueberry Growers Association, Grand Junction, MI. Personal Communication of Nov. 9, 1964, from E.H. Barnes, Assistant Professor of Plant Pathology, Michigan State University, East Lansing, MI. were collected with a D-VACR sampler and determined by that author with the assistance of Louise RusselA. Marucci5 reported that similar aphids determined by systematists at the National Museum were identified differently in successive years, i.e. Amphorophora vaccinii, Masonaphis azaleae, Fimbriaphis sp. and Masonaphis pepperi. Pepper6 has supplied this author with slide mounted specimens of L, pepperi and E. azaleae, and has never collected the latter on blueberry in Pennsylvania. Aphids collected from cultivated highbush blueberry (Vaccinium corymbosum L.) and caught in plant traps in western Michigan in July of 1979 were determined as l. azaleae by Dr. Monya Stoetzel7, but these specimens were not slide mounted for identification, and the characters for keying the species are very difficult to discern on unmounted specimens. In an effort to clear the taxonomic problems, specimens 4L. Russel, Aphid Systematist, (Retired), USDA Insect Identification Laboratory, Beltsville, MD. 5P. E. Marucci, Research Professor in Entomology, Rutgers University, Chatsworth, NJ. Personal Communication, 1979. 6J. 0. Pepper, Eremitus Professor of Entomology, Pennsylvania State University, University Park, PA. Personal Communication, 1980. 7M, Stoetzel, Systematist, USDA Insect Identification Laboratory, Beltsville, MD. have been sent to M. Stoetzel, M. E. MacGillivray, J. 0. Pepper and V. F. Eastops. Specimens have been returned by J. 0. Pepper and M. E. MacGillivray, determined as Illinoia pepperi. Specimens sent to M. Stoetzel were determined only as Illinoia sp. 8V. F. Eastop, Insect Systematist, British National Museum, London, England. BiolOgy of Genus Illinoia (= Masonaphis) MacGillivray (1958) listed the following host plant families for the subgenus Ericobium; Cupressaceae, Abietaceae, Liliaceae, Caprifuliaceae, Compositae, Corylaceae, Ericaceae, Hydrophyllaceae, Myricaceae, Ronuculaceae, Rosaceae and Violaceae. A preference was noted for the Compositae and Ericaceae. She also stated that the species for which biological data were available were monophagous or oligaphagous. Host alternation was not noted. Sexual forms were found only in autumn, no association with ants existed, and these aphids did not deform the host plant tissues, i.e. cause galls. Extensive biological data are available for I. maxima (Mason) (Subgenus Oestlundia), the thimbleberry aphid. This aphid is holocyclic with all morpholical forms occurring on a single host species, Rubus parviflorus Nutt; plant-aphid-parasitoid relationships have been studied and modeled (Gilbert and Gutierrez 1973; Gilbert et. a1. 1976) The following description of the biology of £,'maxima is taken from Gilbert and Gutierrez (1973). Eggs are laid in leaf litter during the spring and summer, and diapause until the following spring. After hatching, lst instar nymphs walk into the bushes to the tips of the canes, where they develOp into parthenogenic females (fundatrix). These have two types of progeny, termed gynoparae and virginoparae. GynOparae eventually give birth to sexual females; virginoparae give rise to further parthenogenic females and sexual males, as outlined in Figure 1. Sexual forms first appear in the second generation, and continue throughout the grOwing season. Males and gynoparae forms are winged, sexual females apterous, and the virginoparae may or may not have wings. Adult 1, maxima move away from the terminals on which they matured. Sexual females move to the base of the thimbleberry plants, before laying a maximum of 8 overwintering eggs in the leaf litter. Color differences make morph identification easy for I, maxima; males are red, sexual females white, and the parthenogenic forms are green. GynOparae and winged virginoparae are indistinguishable unless their progeny are observed. The base temperature for development of this aphid is 3.30C (38°F). Few studies have dealt directly with l. pepperi. Earlier studies have indicated that this aphid is mono- phagous on highbush blueberry (even limited to certain cultivars) or rarely oligophagous, with no alternation of hosts; winged viviparous forms were generated throughout the growing season, and the overwintering strategy remained under investigation (Elsner and Whalon 1980). Both green and red colored morphs of A, pepperi were found in the study, but the red forms were a color phase of apterous or alate viviparous females, not males as in the case of 3, maxima. .Ammma umuumuau can uumAHHuv mauoamw>hmm.m=nnm no Acomwzv maaxma maoaHHHH mo macho mmwAII.~ .me 2a! 2a: 23¢ 2000:0533 Acooocofiiav 232.2233 2002.65.63 22.2.3.5 I «.3059; H 22.2.3.5 l1. 22.2.3.5 ll. 5.325.. \ \ .1 232.2353 “502.2933 , 23235.03 5.3025533 82.230 9.2.230 82.230 22.055 0.2.5.. 0.25.... 22.3.. now II .I | ll loom III II I loom “05.25230 10 Giles (1966) gave the distribution of blueberry aphids in Michigan (Figure 2) and partially described the biology and behavior of l. pepperi. Table I gives the relative incidence of the species collected in his study by sampling with a D-VACR unit. Table 1. Percent of Commercial Blueberry Plantations Infested with Illinoia pepperi and Ericaphis 'scammelli from 1961-1964 (Giles 1966). Relative Abundance of Species Year I, pepperi E, scammelli 1961 13.0% 6.72 1962 34.22 10.5% 1963 20.02 3.3% 1964 28.0% 12.0% He reported that the preferred feeding site for both of these aphids was the upper surface of leaves at the base of the bush. He found no aphids on the roots of blueberry. Blueberry Shoestring Virus Disease Blueberry Shoestring Virus (BBSSV) disease was first described in highbush Blueberry (y, corymbOsUm, 'Jersey' cultivar) in New Jersey (Varney 1957) which is considered to be its point of origin. Since that time, the most probable mode of dispersal to many other states has been 11 -.._r-___. ....-. ..-. “""_°""“—l’""""' MANISILL' WEXFORO! mswmimomoui OGIMAwi '0 5 c o i . i W-.AT-,._ MASON] LAKE ioscmu! CLARE mrww'j' ‘L MIGOSIA :Ni I IISABILu' "MIDLANO (V ......._..I.__.. c.__r" ' '1]- ruscou ° smnuc ' MONTGALM rmymr' SAGINAW ' I .. L. ...—.... . c .. u RICO}?! I; | . - L [L1 . t-- -- -- - ...... ---- : mt ' tom lcumoulsuumsu" “"5“! F'cwa O 'L'HTJ'T'J ,g?_l_l_fl" F;7 mom I may I (”OH iINcIIAM lumucsmu! “mo ,G-r G-G-T-.4—~G-' .: “3W immune! umcuu I JACKSON lwnsmuuw.‘ III-mu ._.+....l...__r.L.. ' . ' u . CASS iSYJOSLPH! BMNCN iHout-o‘ul LCNAWKE [MONROE .222. .--.i. .--.i.._...i I .1 L.— .——‘- --"" " I Ericaphis scammelli (Mason) E: Illinoia 2223.121 (MacGillivray) FIG. 2.-- Geographical distribution of blueberry infesting aphids in southern Michigan (Giles 1966). 12 through diseased propagation stock. Lockhart and Hall (1962) reported apparent visual and symptomless infection in lowbush blueberry, y, angustifolium, in Canada. Hartman et. a1. (1973) visualized the virus-like particles in plant tissue using electron microscopy. The small spherical (27mm in diameter) virus has been purified and shown to cause the disease (Lesney et. a1. 1978). Ramsdell (1980b) has characterized the virus and adapted the Enzyme Linked Immunosorbent Assay (ELISA) techniques of Clark and Adams (1977) for use in the detection of BBSSV infections in blueberry. The ability of l. pepperi to be a vector of BBSSV was demonstrated in 1978. Successful transmission of the disease occurred only with 2 minute aquisition times and 100 hour inoculation periods only (Ramsdell, unpublished data). No other vectors have been determined. ECONOMIC JUSTIFICATION Michigan ranks first worldwide in highbush blueberry production. The annual yield exceeds 35 million pounds, constituting over 30% of the North American crop. In Michigan, blueberries are grown on organic soils with a pH from 4.0 - 5.5 and a high water table. Few other crops grow well in sites suitable for blueberries. The demand for good blueberry sites has raised the land values of what was previously unused areas. Based on an estimated 1980 crop of 37 million pounds and an average sale price of $0.35 per pound (1980 prices ranged from $0.75 per lb. for roadside sales to $0.35 per 1b. for processing grade fruit), a conservative estimate of the value of last year's crop is nearly 13 million dollars. Current highbush blueberry acreage production in Michigan is approximately 10,000 acres. It is estimated that another 1,000 acres have been planted but have not yet reached bearing age (8-10 years)9.q Highbush blue- berries will continue to be productive for well over 30 years if properly managed. Some fields in New Jersey which were planted in the early 1900's are still in production. 9J. Nelson, Director of Research, Michigan Blueberry Growers Association, Grand Junction, MI. Personal Communication, 1981. 13 14 Many varieties of highbush blueberry are grown in Michigan. All have been bred from natural strains of y, corymbosum. The most popular cultivar is Jersey, which accounts for well over 50% of the acreage. Other common cultivars include Bluecrop (14%) and Rubel (12%)10. Bluecrop is apparently resistant to BBSSV but it is very difficult to propagate. Each cultivar has certain favorable characteristics which make it more applicable to the varied utilizations of blueberries. Blueberries are sold as U-Pick, or harvested by hand or machine for fresh pack and processing grades. Table 2 gives the typical utilization breakdown of a year's crop and the prices received for selected years. Table 2. Crop Utilization and Average Market Prices for Michigan Blueberries . Utilization % of Crop Avergge Price/lb. (Grade) 1980 1970 1972 1975 1980 Fresh Pack 20 . $0.50 Process 75 $0.20b $0.30b $0.25b $0.35 U-Pick 5 $0.50 — 0.60 aSource = J. Nelson, Director of Research, Michigan Blueberry Growers Association, Grand Junction, MI. bAverage price received, all grades. 10J. Nelson, Director of Research, Michigan Blueberry Growers Association, Grand Junction, MI. ’Personal Communication, 1981. 15 Prices are influenced by the size of the crop, environ- mental conditions (frosts, hail, excessive moisture, etc.), market competition with other fruits, and consumer demand. The 1972 crop illustrates the influence of weather and subsequent price variation; the crop was greatly reduced by spring frosts. Prices rose accordingly and demand for quality berries was high. Yield per acre varies due to soil conditions, variety and condition of plants, but averages nearly 4000 lb per acre in well kept plantings. At the average 1980 price of $0.35 per pound, an acre of blueberries would produce $1400 worth of fruit each year. Energy inputs into blueberry production include pe- troleum products (fuels, fertilizers and pesticides). Cultural techniques contribute to the intensity of energy inputs as does the level of weed or pest control utilized. A good deal of human energy is also needed for successful blueberry production, due to manual labor inputs necessary for pruning, hand harvesting and packaging of the product. Table 3 presents a breakdown of the estimated fixed costs per acre per year for blueberry production in Michigan. 16 Table 3. Highbush blueberry production costs. 1981 estimates. Operationa ' Cost/Acre/Yearb Fertilizer $45.00 Herbicide 25.00 Phomopsis Canker control 55.00 Mummyberry control (funginex by airplane) 75.00 Pruning and brush chopping 180.00 Mowing or cultivation 30.00 Bee rental 25.00 Depreciation on plants 200.00 Taxes 50.00 Gasoline 15.00 Pesticide applications (by air) 60.00 Estimated Total $760.00 aTypical operations. Individual grower situations or decisions may increase or decrease the number of pro- duction operations. bSource: J. Nelson, Director of research, Michigan Blueberry Growers Association, Grand Junction, MI. This table does not include the costs of harvest, so this total is underestimated. A grower with a large operation (70+ acres) may pay up to $30,000 per year to employees, mostly during harvest. Custom machine harvesting is avail- able for $0.10 - $0.12 per lb. l7 Extent of BBSSV in Michigan Yearly surveys have been made for plant diseases (mostly BBSSV, and Stunt, a mycoplasma disease) in blue- berry since 1957. In 1976, 5,724 BBSSV infested bushes 'were found on 1576 acres surveyed. If this acreage was representative of the 10,000 acres in production, there were approximately 36,600 infected bushes in Michigan in 1976. Figure 3 shows the increase in visibly infected bushes for the last 25 years (figures were estimated in the same manner as the example above). From Figure 3 it is apparent that by 1985 there could be over 100,000 plants with visual BBSSV symptoms in Michigan. BBSSV may have up to a 4 year latency period before visual symptoms are expressed. Because of this the actual number of infected bushes at any time is much greater than the number of plants showing visual symptoms. It has been proposed that there could actually have been over 145,000 infected bushes in 1976, compared to the visually based estimate of 36,000 (Ramsdell et. a1. 1980). Losses Due to BBSSV Infection by BBSSV reduces a bush‘s production. At some point this declining yield renders a field an economic loss, making removal of diseased bushes and replacement ‘with new plants necessary. Even before production drops significantly, the infected bushes serve as an inoculum source for the infection of other bushes, and should be FIG. 3.--Observed [*] and extrapolated [I] plants with visual symptoms of Blueberry Shoestring Virus disease in Michigan from 1957 - 1985 (Ramsdell et.al. 1980). Y = number of infected plants; X = year. 18 1985 mll/ G1|. [2.]! . / r // r / v / .1 r5 e tn. 2 vi 7 r 2 .. VA 1 ... H 9. Y 7 ”5 9 6 8 I9 _ r1 0 G : r T Y G .5 5 1 d 111 4 d 4 ‘ d 1 d4< 4 d 1 w ooQoo. . ooqns . ooQoo OQQmN o mGzcgm >xmmmm34m QMGummzm .oz YERR FIG. 3. 19 removed for this reason. Currently, removal of infected bushes is the only effective solution to BBSSV problems. The problem.of latent infection renders bush removal practices less than perfect for complete removal of diseased bushes from field. Individual diseased bushes are often removed and replaced if a field is lightly infected. The practice is favored because the entire field does not have to be removed from production. Severe infections call for the rouging out of entire fields and starting over. Costs for removal of diseased bushes is approximately $1,000 per acre. A two—year waiting period is recommended before replanting. The decision must then be made to plant a potentially resistant cultivar such as Bluecrop or one which is more suitable for other reasons. Site preparation starts with the complete removal of plant material when the old bushes are removed, leaving no stumps or roots. Before replanting, soil modifications may be made to favor the new planting and adjust the pH. Two year old plants certified free of disease should be used to replant the field. A typical planting scheme (4 x 10 ft. spacing) takes 1089 plants per acre. Typical costs of replanting with the resistant cultivar Bluecrop are given in Table 4. 20 Table 4. Approximate Costs Per Acre for a Removal-Replant Operation as a solution to BBSSV disease in Western Michigan, 1981. Year Operations Main Inputs Extra Costs Fixed Costsb Totals 1 removal, energy $1000 $200 $1200 sanitation labor 2 soil energy ---—- $200 $ 200 management labor 3 replant energy $2000 $300 $2300 plants labor 4+ management energy ----- $760 x 7 $5320 labor 10 year total $9020 aSource: J. Nelson, Michigan Blueberry Growers Association, Grand Junction, MI bFigures given are modified values from Table 3, as explained in text. Figures given for fixed costs in Table 4 have been adjusted downward from those found in Table 3, since during the first 3 years of the replant procedure, certain operations, i.e., pruning, bush chopping, mowing, cultivation, bee rental and pest control are reduced or eliminated, thereby lowering COStS . 21 Besides the direct costs due to the removal-replant operation itself, revenues are lost for the years that pass before the new bushes become productive (roughly 8 years to full production). On the average, the yield from an acre of blueberry plants is worth $1400 per year. This revenue is lost completely for the first few years, and can be slowly regained as the planting matures. Considering this lost revenue as another cost of the removal-replant operation, the total cost over a 10 year period could approach $14,000 per acre. It has been estimated that if all the known BBSSV infected acreage in Michigan were renovated, the total cost over 10 years would exceed $3,000,000. This would of course be accom- panied by a significant loss of production and allied reductions in support industries, labor, etc. BLUEBERRY SHOESTRING VIRUS DISEASE Symptomatology and Host Range Blueberry is the only known host of BBSSV. The disease has been observed in the cultivars Burlington, Coville, Earliblue, Jersey, June, Rancocas, Rubel and Weymouth (Ramsdell 1980a). The cultivars Bluecrop, Northland and Bluejay appear to be resistant to the disease. Visual symptoms of BBSSV are as follows: 1) Narrow or strap like leaves: hence, the name shoestring; leaves may also be crescent shaped or curled, 2) Elongate red streaks: on current years stems; sometimes visible on older wood, 3) Red vein banding: on young tender leaves; along midrib or in oak leaf patterns, 4) Immature berries with purplish cast: apparently normal when ripe; no quality loss, 5) Twisted appearance to stem growth: also weakened and spindly wood; easily broken in wind or under fruit loading. Symptoms on leaves and stems are most pronounced on vigorously growing tissues, especially near the base of the bush. Environmental conditions enhance or repress the expression of symptoms, even on bushes which were quite obviously infected the year before. Such was the 22 23 case in 1980 when many infected bushes did not express symptoms, or visual symptoms were repressed. True symptomless infections are quite common due to the latency period. Various immunological techniques are available for the detection of symptomless BBSSV infection. ELISA has proved to be reliable and accurate. Several new techniques are currently being tested for use in BBSSV detection in both blueberry tissue and the aphid vector (Ramsdell, unpublished data). Aphid TranSmission Transmission studies by Ramsdell (Unpublished data 1978) produced successful inoculation under very specific conditions; only aphids which had a 2 minute acquisition period and a 100 hour inoculation time transmitted the disease. Table 5 presents the results of these transmission trials. Much work remains to be done to verify these results. From the existing information, the virus appears to be semi-persistant in £,'pepperi. It may be circulative but is probably not propagative in the vector, as virus titre is quite low in aphids. Illinoia pepperi appears to be an inefficient vector in the field. Infection rates are low and the disease spreads slowly through a planting. From 1959-1960, a 0.9% increase in infected bushes was found in one field. Lesney et. a1. (1978) calculated a "compound interest rate - (r)" for observed field spread in 1958 to 1959; the value 24 .mEOuoahm mafizonm mac haao up: .>mmmm How o>fiufimoa amu .muamao coupon mm wow: humonosan .hmmHOH..wo wwcfiuuso vauoou vommomfinn .coaumn aoaumfisoom «Momma use: H um>umum mums mwa3m< .vwma uamHm umou you mufizmm aoam m\o m\o m\o m\o m\o Houuaoo pagan so: m\o m\o m\o m\o m\o Houuaou wanna m\o m\o m\o m\o m\o muse: cm 2o m3 20 So So .8: H m\o m\~ m\o m\o m\o nuances N meu a use: OOH use: «a use: H :Ha 0H mafia mmouow u Adowufimaaoo< .uwaau,wmwvoww cowumasoocH .Awsmu «one vmsmwansna: .Haoumammv mfiummmwm,maoaHHHH an dogmmfiEmcwuu maufi> wafiuumoonm huumnoaam mo momma .m canny 25 was 0.269/unit/year. Other tests showed that infection occurred on a bush to bush basis along rows, and only occasionally across rows. Personal observations have confirmed this. Spread of the disease was determined not to be due to continuous re-introduction from sources outside a field (Lesney et. al. 1978). Because of this pattern of spread, it can be suspected that apterous or immature aphids walking from stem to stem may be the most likely vectors of BBSSV. In most plantings, bushes within a row overlap somewhat so there is ample opportunity for aphids to move from one bush to another. Moving from row to row is significantly more dangerous to an aphid due to factors of distance, terrain, desiccation, starvation and ground dwelling predators. Infrequent transmission by winged forms or far ranging walking indivi- duals may account for the spread of BBSSV to other rows. It would be worthwhile to study the spread of BBSSV in younger plantings, or closely trimmed fields where bushes do not touch along the rows. A different rate or pattern of spread under these conditions would be expected. OCCURRANCE AND DISTRIBUTION OF BBSSV IN OTTAWA CO., MI OBJECTIVES Fields were surveyed for BBSSV infection in order to determine the seasonal and locational differences in symptom expression, spacial distribution and pattern of spread, and the relationship of field location, design and surroundings to the incidence of BBSSV disease. METHODS AND MATERIALS Five plantings of blueberry ('Jersey' cultivar) located in Ottawa County were chosen as the main study fields. Each was owned and operated by member of Michigan Blueberry Growers Association, Grand Junction, and were designated by their field numbers as listed by the Growers Association. The fields, from south to north were: #393, Park Township, Wesley Waldron, owner; #7, Port Sheldon Township, Allen Devries, owner; #54A, Olive Township, Vern Brower, owner; #54B, Olive Township, Vern Brower, owner; #281, Polkton Township, Frank VenRoy, owner; Historical maps of disease incidence were available for field #7. Field #54A and B are adjacent to each other, but have had different histories of disease incidence. Diagramatic maps of each field can be found in appendix 2. 26 27 Field #54B was examined for the effects of exposure to sunlight on symptom expression. Earlier workers sug- gested that symptoms were more vividly expressed on the sunny sides of bushes. Rows in #54B were east-west oriented, so there was a sunny (southern) and shady (northern) face of each row. Each row was surveyed for visual BBSSV symptoms from both sides, and diseased bushes recorded. This survey was made on July 23, 1979. Fields #393, #7, #54A and #281 were examined for visual BBSSV infection on June 28 and August 8, 1970. Infection was determined based on the observation of visible symptoms. Teams of two people examined a row (one on each side) and tagged diseased bushes with plastic ribbon. Tagged bushes were later recorded and mapped. Data was converted to a computer matrix form to be compared and analyzed for rate, direction and proximity of disease spread. It was planned to repeat this survey in 1980, but environmental conditions repressed the expression of symptoms on diseased bushes. RESULTS No significant difference in symptom expression was noted between sunny and shady sides of bushes or rows. As can be seen in Table 6, roughly equal numbers of bushes were expressing visual symptoms on the north.side only, southside only, or both sides at once. 28 Table 6. Differences in BBSSV Symptom Expression on North and South Sides of Blueberry Bushes. July 23, 1979. Bushes examined Healthy SymptOms - North only South only Both- 382 310 23(3l%) 25(34%) 24(32%) These results imply that inspection of bushes from one side of a row only would not accurately determine the state of infection in a field. On the average, a 1.9% greater number of visually infected plants were found on August 8 than on June 28 (Table 7). Table 7. 1979 BBSSV Survey Results: Number of Bushes with Visual Symptoms on June 28 and August 8. June 28 August 2... Field Total Bushes Infected % Infected % % Increase 7 1740 405 23% 431 24.7% 1.4% 54A 680 34 5.0% 47 6.9% 1.9% 543 382 -—- -- 723 19.0743 G—- 281 3454 376 10.8% 458 13.2% 2.4% aFields 54B examined only once on July 23, 1979. 29 Fields #54A and B, although adjacent, Show a quite different infection rate. This can be partially explained by a more extensive diseased plant removal program in #54A. Computer matrices for all fields except #393 were generated with different symbols representing the bush conditions, i.e., normal, expressing symptoms on June 28, expressing symtoms on August 8, and removed. Field #393 had unequal bush spacing, allowing for different numbers of bushes in rows of the same length. It was therefore difficult to convert to a matrix form, and was analyzed by directly examining the field data. Maps generated for the fields were easily studied. A portion of the computer generated maps for fields #281 and #7 are shown in Figure 4. Direction effects on BBSSV infection were evident from these maps. Spread was mainly within rows and occasionally in other directions. These results supported the findings of Lesney et. a1. (1978). Field #393 showed a greater number of infected bushes in the southern half of the field. Field #7 exhibited greater infection in the center and western portions. In #54A and B, greater infection was found in the northern end of the field. Field #281 had a rather even distribution of infected bushes, but increases could be seen in the west and south- east. Since there is no consistent compass direction in which greatest infection occurs, it is likely that field layout and surrounding areas have mmre relation to infection 30 SHOESTRING VIRUS FIELD MAP-- Field 281 . . . . . . . J . . . . . . . . . . . . . . . . . . . . A A . . . . . . . . . . . . . . . . . . . . . . . . . . . J . . . . . . . . . . . . . . . . . . . . . A . . . . . . . . . . . . . J . . J . . . . . . . . . . . . . J . . . J . . . J . . . . . . . . . . . . . . . . . . J . . . . . . . . . . . . . . J J . . . . . . . J . . J . . . . . . . (.4 o Lat-4. La. 2...... L. HOHHOOH>L¢00¢ H0 ‘40 “LOGO. 0 0 H0 HHHL‘O 0 L! h‘d‘d‘d - o LIL-GHQ. L. o o Lgoqu o QHHH Ho (... Rows run north-south Key to symbols: . - bush without visual symptoms J - bush with visual symptoms on June 28 A - additional bushes with symptoms on Aug. 8 * - stump of removed bush with infected shoots ) Space( - removed bush FIG. 4.- Sections of two computer generated BBSSV infection maps from 1979 survey, Ottawa CO., MI. 31 rate, probably due to the influence of these factors on aphid populations. Field #393 is a relatively old field, with a long history of BBSSV problems. Along the western half of the northern border is a small deciduous woodlot with a few coniferous trees. To the east there is a drainage ditch lined with deciduous trees, with field crops beyond this. Until recently, there were more blueberries just to the south, but this planting was heavily infected and removed. It was replanted in 1980. Farther south are more blue- berry plantings. To the west is a roadway, and a coniferous woodlot; beyond this lie more blueberries. The greater infection rate in the southern half of field #393 is pro- bably related to the former heavily infected planting to the south. Field #7 is also an older planting. Records of disease incidence for this field are available as far 11 To the north of the block is another back as 1957. blueberry planting, part of which is very recent (3-4 years old). To the east, west and south are blueberries of similar age. A woodlot is visible toward the west. There appears to be no obvious reason for the distribution of infected bushes in this field. 11J. Nelson, Director of Research, Michigan Blueberry Growers Association, Grand Junction, MI. Original materials and mimeographed reports. 1979. 32 Field #54A is long and narrow, with the long axis running north-south. To the east is an open lot, followed by another blueberry planting. The open lot was once a planting as well, but was removed due to disease problems several years earlier. South of this field is a residence, and a small field of blueberry. West of #54A is field #54B, and some young pines. U.S. 31 lies farther to the west. The north end of field #54A is adjacent to a small pine woodlot, which partially surrounds this end of the field. Beyond the woodlot are more blueberry plantings. Greatest infection was noted in the northern portion of this field, and may somehow be related to the woodlot. The easternmost row was also quite infected, probably due to the former field with disease problems. Field #54B, immediately west of field #54A, has similar surroundings. A pine woodlot is northeast of this field, and it is bordered on the west by U.S. 31. Once again, increased infection seems to be in the area nearest the woodlot. Many open spaces are present in this portion of the field, due to removal of diseased bushes. Field #281 is a relatively younger planting, and is managed as a clean culture system; all other fields had herbaceous ground cover throughout the year. To the north of the field lies another planting of blueberry, the infection status of which is nOt known. A small deciduous woodlot lies to the northeast. Raspberries and strawberries 33 are grown to the east of this field, and farther east lies a residence. The south border of the field is a gravel road, across which lies an open field where some livestock are grazed. A large mixed woodlot lies to the southeast. The west side of the field is bordered by a gravel road, ditch and fence row with trees and bushes. Beyond this is a pasture and dense woods. Although not greatly different in infection rate, the areas closest to the southeast and western woods are more diseased than other parts of this field. DISCUSSION It appears that certain features of the surrounding areas influence the incidence of BBSSV disease within fields; this can be referred to as an "edge-effect". An outside source of inoculum.or vectors often account for such a phenomenon. However, past works have shown that there is likely not to be a significant outside source of inoculum (Lesney et. a1. 1978) and personal observations have not revealed hosts of L, pepperi in areas surrounding the fields, except where more blueberry is presentI I suggest that surrounding terrain and vegetation favor aphid populations in the blueberry fields, and therefore BBSSV spread, by providing protection in the fields from severe weather and other climatic effects. This shall be discussed in greater detail in the section on aphid biology. SEASONAL HISTORY OF ILLINOIA PEPPERI ON HIGHBUSH BLUEBERRY OBJECTIVES Very little information on the lifecycle, seasonal history or behavior of Illinoia pepperi is available from the literature. Because of this, rather than con- centrate on any specific aspects of the life of this aphid, a general biological study was initiated. It was assumed that through the course of such a project, the areas of key interest in future research would be identified. METHODS AND MATERIALS The majority of this work was conducted in fields #393, #7, #54A and B, and #281. Other western Michigan fields were also visited frequently. One central Michigan field12 was of particular interest and often visited since no insecticides are used in the management of this planting. A very natural state exists in this field, with effective biological control of many insect pests. Yellow pan traps were used to monitor the flight of alate aphids in fields #393, #7, #54A, and #281. Plastic dishpans (30 cm x 38 cm x 16 cm) were used for pan traps. 12Eaton CO., MI. 3.5 miles southwest of Charlotte, Lowel Cook, owner. 34 35 These were placed on wood or plastic stands (approximately 30 cm in height) to provide visibility above the herbaceous ground cover. Traps were filled with water to within 3 cm of the brim. Trap color differed in 1979 and 1980; samples of each are given in figure 5. A rather bright yellow trap was used in 1979; low trap catch and difficulty in obtaining the same brand of dishpan led to the use of a darker color (closer to goldenrod yellow) dishpan for traps in 1980. Five pan traps were used in each field; one at each corner (NW, NE,.SW, SE) and one at the approximate center of each planting. These traps were visited every 2-4 days during the activity period of aphids. Captured aphids were frozen in distilled water or a saline solution (.85%NaCl), or preserved in 70% EtOH. Data pertaining to numbers of aphids, location within fields, and date were recorded. Large screen cages were used to enclose entire blueberry bushes in field #54B in 1980. Cages were erected on June 1. Bases of the cages were buried to prevent walking aphids from entering or leaving the cages. The screen mesh was sufficiently small (8 strands/cm) to exclude alate aphids from bushes. Aphid populations on these bushes were ob- served to study the effects of reduced predator populations and climate changes. Numerical data were analyzed using Chi-Square contin- gency tables where appropriate (Gill 1978). 36 1979 material: Rubbermaid Inc. Wooster, OH. # 2970 yellow 1980 material: Fesco Operations of Cities Services Co. # 2412 gold FIG. 5.-Samp1es of pan trap material for 1979 and 1980. 37 Soil, root, basal stem and leaf litter samples were taken in 1979-1981 to locate the possible overwintering sites of this aphid. Soil and root samples were made using a commercial bulb coring tool in September of 1979 and April 1980. Samples were examined in the laboratory or greenhouse. Samples of soil, roots, basal stems and under bush litter were taken in January and April 1981. These were first examined for the presence of overwinter- ing forms of ;, pepperi, and then placed in a greenhouse and observed frequently for the emergence of aphids. On April 2, 1981, halves of 2 bushes were removed from field #54B and transplanted into an isolated bin in a greenhouse courtyard on the M.S.U. campus. The soil around the roots and base of the bush was kept in place; leaf litter was removed, except that which was lodged between the branches at the base of the half bush. These bushes were examined for the presence of aphids as the season progressed. The movements of late season aphids were closely examined in 1981 to determine their over- wintering strategies and forms. In the field, observations on aphid biology, life history, populations and behavior were recorded during each visit to the study fields. Field weather data was obtained from Environmental Data and Information Service Monthly Summaries of the National Oceanic and Atmospheric Administration. Rainfall amounts were obtained from the 38 stations closest to the study fields. The Holland station rainfall records were used for fields #393, #7 and #54A and B. Rainfall recorded at Nunica, MI was used for field #281. Due to the very scattered nature of summer storms in western Michigan, the amounts reported may be signi- ficantly different from actual rainfall at the field site. Only one local station recorded wind speeds. This was in Muskegon, MI which is 22, 27, 30 and 32 km away from fields #281, #54A, #7 and #393, respectively. Hygrothermo- graphs were used to record temperature data for fields #281, #7 and #54A. Greenhouse cultures of l, pepperi were maintained at 20-25°C on 2-3 year old potted blueberry plants ('Jersey' cultivar). Aphids were transferred regularly to fresh plants to eliminate crowding and preserve plant quality. RESULTS AND DISCUSSION Pan trap catches of alate l. pepperi were quite low. A total of 46 specimens were collected from all 4 fields in 1979. In 1980, only 12 alate aphids were captured in pan traps. Results suggest that further work is necessary to determine a more effective trap to monitor winged l. pepperi. Competition as attractive stimuli between the blueberry leaves and traps may influence trap catch. Analysis of the spectral reflectance pattern of blueberry leaves may prove useful in the selection of trap colors. Refer to Table 8 for the dates of first and last alate aphid captures in study fields. .ONGH «Om USS—.1 HHu—ufi Rx» UHQflM GH VUUMHQ HOG mums» QOHHD .ooq.m mo ousumumasou mmmn .H noun: macaw mmmp mmuwmv vmumassooo ad unmade Hummmmm swooHHHH oumadrl.o .lo 41 o>¢o 33 .3. on: 3! .3. =- 02; .fl. 3.33 . _ _ _ _ _ »8_ .§__ _ .31 >5; B. «:3 : 1... fi v 6.... w m s M ..I . 10.6 ... U V d 3 Guam 3. wow OANE 22 com .3 803.. 50.520... 53.4235. ”up u a u a B .3—2. «9—2 8—: 2_28_2 ...—o. uuuwmm 53 {um _ 03¢ _ :2. — 25.. r u»; D u I. if m 3.. 16“ fl aka, m x. 04w: m 10.9 c. I. U :6: an: a 88:33}: 80.5! p a? a. w .w w L... s . <- « .3 a «a .....3..!. B :3 3 p B v8... 3_- 8.! Jo. 00—2 a”. 45 48:3 _ _ :3. _&m_ ..Imms_ mum}. uuulflsa 10.. a V m m 9 rod m p! 333.38 5: 3:3 chap u ”Scar; 35¢ to 04!... v opcoeazolp<§¢8 '3 u mzeiggolgnhupo: :9. use 10.» 90:62.2 3.95! «w... «a: (”a c»: (”a Ea: an» 2.2:... 5 z: a a a .. CONN 00—0. 8—5. .Q_Qp '0—pp QM. J” bfl‘ "“8 .62 Lalufi .81 5:; 95.. ~23 10., i i i .. . m a i . . chap . _ F loo .0. man Dam-.... m 6.. A>UI “av 3 '0‘ 96:32: macs-u. .r c, r r 4P ? by M 5...... B 5 n B . UHh .maouumoaanam ovwoaumoa can maawwawmu unmowmaomwm mo mmuwv mnu ouwoawsm msouu¢ .owma ..«z ..oo wamuuo aw mamuu can 3oaamm aw unwamo mummmomwmfioaHHHH muderl.n .uHm 42 .n .95 34.. >49 00-.- 00—0— pO—Q- hb—pu “fl. NO—O “U53 . 'b—NN vh—Op 00—0. .0—wp QM. bdh p~_0 U898 .23 _ ...54— 5.... _ 0...... - 34¢ .50 _ .....uo _ .34 _ >4... _ 9...... h =49 IOJ rO.p V to.“ M . .3 .- 32.3359 3.. .24.. v coo p m 6.3.39.3: m 3... 3m... . .. on... . to. ..u. 44.54 a» :95 34: ca 04m: 5. u n In! 20.35.434.64 .5 n I 25:40:34 950.3 a 65.. w :3. was ...... u . n w 5.4 4 88:42 :9. 38 4h- » .p 29. we» a 30.52 .m: b. h. b. b. y 30:40:34 4. 4.. 4.. 4.. 35:3; 54.93.4544: a n» B h w» w a” sinusitis. annup ” pumps» “’3 34a 3: 2: 34. .4: no. .3 “Runs on: 3.. :2 22 32.3. 4; .3 34a _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ is. .50 . Haw. — .34 — >42.— uic. 9—40 .50 — is: b .034 _ >42. _ $5.. _ 34: fl # r9. — — ...... 334.55.. 5.. .340 v .zo.»4o.at4 44.304 rod m .65 M 5.! 0» cost 84.. [at n a 2.849: 9.349 a 85.. coop ... on: a s ad... I... m no... 3m... .2 u .. ... 25.. was rod :9. an! ...... squads...“ b. .w a. .r as. .... .33..“an » p a p p . 4. 4o 4.. 4... a 4.. 4o tongs-4: a: u u u a a a B n u a: ......o 23...: B: u u p p u u S p w B: 43 The trap catch for field #393 in 1979 suggests two periods of peak flight activity; one in mid June to early July and another in late July to early August. This pattern was not demonstrated in other fields. Directional differences in the numbers of alate l. pepperi caught were noted. Table 9 presents the directional breakdown of the 1979 trap catches. Table 9. Directional analysis of alate Illinoia pepperi caught in Yellow pan traps in blueberry plantings, Ottawa CO., MI. 1979. Trap _ a Field Location #393 #7 #54A #281 NW 2 l 4 1 NE 17 1 2 0 SW 0 l 1 SE 0 0 0 6 C O 0 0 Totals 29 2 7 8 aNo traps placed in field #7 until July 3. This analysis showed a significant (P i 0.01) relationship between pan trap locations and the numbers of alate aphids caught in 1979. The areas surrounding the fields were examined to develop possible explanations of directional effects, even though the small number of aphids caught may not re- present the field situation accurately. Of the traps in field #393, the southwest and northwest had the greatest 44 visibility range, and was also exposed to a greater amount of wind. The northeast trap was in an area protected from most winds, and closest to a dense woodlot north of the field. Immediately to the east of this trap was a drainage ditch with heavy shrubs and deciduous tree growth. No other plantings of blueberry were close to this corner of field #393. No conclusion was reached as to the reason(s) for the high catch in this trap. Due to the later starting date of trapping in field #7 and the very low number of aphids caught there, a meaningful analysis of the areas surrounding this field is not possible. In field #54A, the majority of aphids were caught in the northern traps. These had less line of sight visibility than the traps at the south end of the field, but the pine woodlot to the north of the field, probably reduced wind speeds thus improving the aphids ability to land in the trap. Aphid pOpulations were also greater in the northern portion of this field. This combination of greater numbers and more favorable flight conditions may have led to the greater trap catches in these locations. It is interesting to note that the northern portion of field #54A has a greater BBSSV infection problem as well. In field #281, the south- east trap produced the most aphids in 1979. This trap was visible from great distances, but was notin an area sheltered from.winds. The trap was closest to the large 45 mixed woodlot southeast of the field. Once again, the same region of the field also had significant BBSSV disease incidence. No single factor, i.e. shelter from wind, BBSSV infection, visibility or nearby vegetation, seemed to be correlated with the greatest trap catch in all fields. These relationships may not be determined until a more efficient trapping technique for alate I. pepperi is discovered. Two other visually similar species of aphids were commonly caught in greater numbers than I. pepperi, making it necessary for close examination of specimens removed from pan traps. These species were Acyrthosiphon pisum (Harris), the pea aphid and Macrosiphon euphorbiae (Thos), the potato aphid. Cornicle morphology can be used as a "quick" field separation of these species using a hand lens. Cornicles of I. pepperi appear swollen while those of A, pisum and g, guphorbiae are cylindrical or tapering. Overwintering, Site Determination -- No forms of Illinoia pepperi were found in soil and root samples taken in 1979 or 1980. Caged bush examinations in 1980 showed the presence of both immatures and adults inside cages at the same time as the rest of the field. This led to the conclusion that I, pepperi did not necessarily overwinter outside the field and re-infest blueberry in the spring; 46 overwintering occurred somewhere on the bush or in the leaf litter below the bushes. No forms of I. pepperi were found in the leaf litter or on the stems collected in December 1980 through April 1981. However, aphids did appear on the succulent basal growth of the half-bushes in the greenhouse courtyard by May 20, 1981. This information suggested that the overwintering form must be closely associated with the basal area of the blueberry bush, as it seemed not to be in the leaf litter or on stems. Close observations in the fall of 1981 led to the discovery of oviparous females and overwintering eggs on the smallest basal shoots. These shoots are usually destroyed by freezing temperatures. 1980 and 1981 stem samples were apparently taken to late in the season for these shoots to be found. The eggs probably fall into the crevices and sheltered areas in the crown of the bush. The oviparous females and eggs are discussed in greater detail in the following section. Biology g; Illinoia pepperi -- A life history of I. pepperi is shown in Figure 8, based on greenhouse cultures, field observations and the literature (MacGillivray 1958; Gilbert and Gutierrez 1973). The first generation apterous female (fundatrix) develops from an overwintering egg in or near the base of a bush. Adults of this morph could be found from.May 19th to June 4, 1981, in the Charlotte field .ammwnomz .5 Agmonguou 6933026 human—039 :25.le so 7336 325% 38:3 .3 393 3.3!... .3... 47 .m .UHm cm02m>oz IcmehOO ouoo octo~c.3..o>o 22:3» ><2 032.2 x3225“. mmmthawm 5:22.00 :34 IPGDGD< souaJ / 0342 .25... v2.4.9.0 : ego-(A (\ou.o.a< V oa.o.a£u~)l\)|--J ' " 398 " 285 289 " 116 54A 272.0 L‘UJNH 281 16.4 m 947 " 474 151 " 219 223.9 «FWNH aRandomly selected and assigned numbers 1-4 for each field. Significant variation in aphid density within fields can be seen. Some of this difference can be explained by varying bush size within fields, but other factors are apparently involved. Field #7 had a denser canOpy of leaves than did fields #54A or #281. This could provide greater protection from severe weather and pesticide applications and therefore allow for greater populations of aphids. 70 Actual densities for each row section were arranged into naturally apparent classes: 1) 0 < density 1 125 per 8.2 meters, 2) 126 < density 1 3) 401 < density i 4) .601 < density i 400 per 8.2 meters, 600 per 8.2 meters, a per 8.2 meters, Values for all sample means, average sample means, acutal densities and average actual densities are presented in Table 14. Table 14. Actual densities, average densities, sample means and averaged sample means of Illinoia pepperi on 'Jersey' cultivar blueberry. Data are arranged by ascending ., order of actual densities and grouped into levels. Actual Sample Means Density/8.2m Leaves Stems 5 10 15 20 5 10 15 75.5 0.00 0.20 0.13 0.00 0.80 0.30 0.13 109.5 0.20 0.00 0.13 0.20 0.20 1.60 0.33 116.0 0.00 0.00 0.20 0.25 0.00 0.80 0.87 average - 100.33 0.07 0.07 0.16 0.15 0.33 0.90 0.44 237.0 0.00 1.50 0.07 0.40 0.60 1.40 1.87 285.0 0.80 0.10 0.07 0.40 0,00 1.00 2.50 289.0 0.60 0.00 0.67 0.15 0.20 0.30 2.00 average - 269.66 0.46 0.53 0.45 0.33 0.27 0.90 2.12 398.0 1.60 0.20 0.27 1.05 1.20 1.30 1.87 411.0 0.20 0.60 0.27 0.70 5.60 7.70 6.20 473.0 5.40 1.30 0.53 0.25 2.20 5.50 5.10 average - 427.33 2.40 0.70 0.36 0.67 3.00 4.83 4.39 603.0 0.60 1.70 0.20 0.35 0.60 0.90 7.50 1010.0 0.40 1.60 0.13 0.40 0.00 3.80 2.30 3375.0 4.00 0.20 6.60 4.35 21.40 29.70 12.90 average - 1662.66 1.67 1.17 2.31 1.17 7.33 11.47 7.42 71 Plots were made of actual density vs sample means, actual density vs averaged sample means, and averaged actual density gs averaged sample means. Straight line regression using the least squares method was used to fit a line through the data points of each plot. The regression values were compared using residual analysis. Plots of actual density XE averaged sample means produced the greatest correlation coefficients and lowest residual values. The regression equations and related statistics for these plots are given in Table 15. Table 15. Regression equations and related statistics for each sample type tested. Sample Type Regression Equationa Statisticsb Y=A+BSZ 2 d r R s STEMS _ 5 Y - 48.6 + 207.3 I .73 .54 6.40 10 Y =-1l.6 + 138.5 X_ .95 .91 8.30 15 Y =---l70.5 + 218.7 x .83 .68 3.61 LEAVES _ 5 Y a 249.8 + 317.6 XI .55 .29 " 7.70 10 Y =-251.8 + 1406.9 X .22 .15 9.96 15 Y s 39.4 + 703.2 x _ .95 .91 1.81 20 Y --109.3 + 1017.0 X .95 .91 1.20 aY-observed density; i=average sample mean; A and B are parameters of the regression equation for the plot of Y vs. X. br=correlation coefficient; R2=coefficient of determination; sd= standard deviation. 72 Samples of 10 stems, 15 stems, 15 leaves and 20 leaves gave the greatest correlation between average sample means and actual densities (Figure 11). The sample technique producing the lowest standard deviations of sample means were 15 stem and 15 and 20 leaf samples. Based on the two criteria of accuracy and precision, the 20 leaf sample was chosen as the most effective sample unit and technique of those tested in 1979. The following method was prOposed for blueberry aphid density determination: 1) take several 20 leaf samples over a distance of 8.2m (25 feet); 2) calculate the mean number of aphids per leaf of each sample, and average these means; 3) use the regression equation Y =-109.3 + 1017.0(X) where X = average sample mean, to calculate Y, the estimate of the aphid population in that section. On August 12 and 15, 1980, four more 8.2 meter sections were counted and sampled in the above manner in an attempt to evaluate this sample technique. Actual counts and calculated values for aphid density are presented in Table 16. Calculated aphid p0pulations averaged 171.2 aphids less (s.d. = 215.1) than the actual numbers present. This result does not support the 1979 findings. 73 10 STE” SRHPLE 15 SIEH SRHPLE' = E g a! 5 a . an I “:0“ 'u u u u u u “I. m “I. ,T 20 LERF SRWLE t i 5‘ ‘fl' g}. 8 ‘§!' 9 0 ”9‘0. 3 . - :1 sg9' :! = - «0311‘. '3' \ ..qfl’ z i...‘ 0 t ‘ g. g o IQ:.. I M . V v f v v '54 u u u u u u FIG.11.-—Plots of observed (actual) density vs. average sample means for four sample types used for estimating densities of Illinois pepperi on mature highbush blueberry ('Jersey' cultivar), Ottawa Co., M1., 1979. 74 Table 16. 20 leaf sample means, predicted densities and actual counts of Illinoia pepperi, August 12-15, 1980. Row section 20 leaf predicted actual difference mean density count 1 0.15 43.3 210 -166.7 2 0.45 348.4 171 +177.4 3 0.35 246.7 620 -373.3 4 0.70 603.0 925 -322.0 DISCUSSION Examination of the field conditions for each year showed that in 1979 favorable climatic conditions and bush growth allowed for a very even distribution of I. pepperi ‘within the bushes. In 1980, harsh weather and fewer succulent terminals near the surface of the bush canopy created an uneven distribution of aphids within the bush; a greater proportion of the populations was in the lower 3rd and inside areas of the bushes. The random selection of terminals or leaves used in the estimation technique were made primarily from the periphery of the canopy. Because of this, most calculated populations were too low. Future attempts to refine the density estimation techniques may be improved by selecting sample units from assigned regions within the bushes; base, interior side of exterior 75 and top of exterior. This change would probably assure a more accurate estimation of aphid populations regard- less of their distributions within the bushes. LABORATORY STUDIES OBJECTIVES The developmental rate, lower temperature threshold for development,generation time, fecundity and life span of I. pepperi are needed to aid in further field studies and the construction of aphid population models. Laboratory experiments were initiated in late 1980 to determine values for these biological parameters of I. pepperi. METHODS AND MATERIALS Colonies of I. pepperi were maintained at 20-24°C on 2 year old potted 'Jersey' blueberry in a greenhouse. All colonies were clones from a single individual, an apterous viviparous female taken in field #54A on July 3, 1980. Laboratory studies were carried out in PercivafE> environmental chamberslB. The food source for experimental aphids was 14 mm circular leaf discs, cut from vigorously growing blueberry leaves on greenhouse plants. Leaf discs were floated upsidedown on a nutrient media (Coon 1959) in 15 x 60 mm plastic petri dishes. The dishes were kept covered to maintain a relatively constant humidity inside. 13PercivalR’model 1-35L, Percival Mfg. Co., Boone, Iowa. 76 77 Mature apterous viviparous females were kept on potted blueberry in a growth chamber at 23°C. Young were removed daily or more frequently, and moved to a leaf disc with a camel hair brush. At this time they were given an identification number and were recorded as 0 days old. Treatment temperatures were 5, 10, 17, 23, 26 and 29°C. Photoperiod was held constant at l6L:8D. Aphids were moved to new leaf discs on a regular schedule to assure quality and uniformity of food source. Observations were made every 24 hours and each aphid's (development noted. The ages at which instar changes, firSt birth of young, and death occurred were recorded, along with notes on behavior and appearance. Progeny were counted and then removed to avoid possible influence of crowding on fecundity. Data obtained from this experi- ment were length and number of instars, generation time, fecundity and longevity. RESULTS Table 17 gives the mean days perndevelopmental stage of apterous viviparous females of I. pepperi as determined in this study. For those treatments in which aphids completed deve10pment, instars per day were calculated and plotted against treatment temperature (Figure 12). Instars per day were regressed on temperature using the least spuares method (Gill 1978). The resulting equation and line (Figure 12) can be used to calculate the development rate of I. pepperi at various temperatures. 78 mono» pausvowm uosu opined mo popes: u mZU ommum wcHuoHano moaned scaumofiflaou ucoaoawmsmcu A coma mo sowumfi>op oncogene ups you owwuu ca show no Hones: some I x «moan mcwuouao engage «a Hones: I as n o o o n o 9 mm m.o q.~. mm m.o o.~ mm umm to n o m.m o.~ OH o.~ m.q um _.H m.m mm m.o m.~ we m.o H.N me com In 0.0 m.~ om c.n o.qH mm m.o s.~ mm c.o o.~ mm m.o a.H mm m.o c.H mm 0mm sq ~.H m.m mm m.w ~.qH No ¢.o o.m Ne n.c m.~ me m.o q.~ cc ..H w.~ me Una In H.H o.HH cm «.0 H.0N oq H.H m.o He m.H m.m we m.H v.0 no o.H _.o «a wad IN «.mH n.~m o n NH m.m m.mH ma m.m m.oH mm. ~.¢ o.mH mm c.c N.ma mu Um 1H mm x on: mm x 2 mm x 2 mm x 2 on x z to x oz musuouoaao QOHMmm aqao< >H HHH HH H new m>HHosaommmm Mot use axon coo: .NH manna .momwp mama pmmaoxo no «summon muoaHHHH mom ousuouomaou ucoaumouu can Ahmp\muwuma«v mums Housmamoao>ov cooSuon nanmcoaumHoMIl.~a.on 79 .Nfi.uHm Aoev wm3h ‘ a A 8 '4 6'3'10'1'2'1'4'1'0'10'23 a: 2'4'2'0 an autumn . untu- 9 '. < a .. . ’ < o i FIG.13, '4 5'0 m'u'u'fc'f. io'u'a'n'io 23': MAR“ “TM I I04 z n I 5'1'0'1'2'I4'1'I'1'a'2'o n 24 2'0 5'50 rsmnm'c NOVA! IV 274'5 a Io'ua'u'u 10 in n 24 u u so unrunuu 'c , .maooa onu uaonm coauww>0p pumpaouo H Muucmmouaou muwm .momap mood pomfiuxo do «smegma mfiocwaaH How ousuuuoaaou ou m>wv woumop :a mafia aowumumcow pom Coupon m>auosvouaouloua uasvm mo awnmaowuoaomnl.¢fl.on 85 .3 .on 8.. 33335.. "rm—55533 2.. ...... on 2 2 3 .... ,9 o m m. a 90-3 3 n... a... 33.. 3 ... a. o. o m P-DPPDDDITDDID-hll I DONF fibbb PDDD Dbl IPFPDII - I d d A. .03 .o« 6! a .8 a. .8. 10h. .0. a e .2: 62 .oo row“ 6a“ .OQN f. .00 .fi .0!“ 50a .4. fl as. 3.5.. .. 3.5332335. 5:9. .2. (0.78 38V” SAVO 338030 '3'.“ NOILVH3N3D "'3" ma: 22.53ng a .2... be... .00“ (00"9'38V8) SAVO 333030 86 Table 21 gives the fecunditv data collected in this experiment. Table 21. Fecundity of apterous viviparous Illinoia pepperi at 6 treatment temperatures on excised blueberry leaf discs with a l6L:8D photoperiod. Treatment TemperatureoC Mean Fec. Sd Most per Female 1 5 2.33 1.21 4a 2 10 6.68 3.60 15 3 17 10.90 7.73 31 4 23 18.67 8.94 37 5 26 _b 6 29 b aaphid had not yet died bno young produced Total fecundity was also greatly affected by the drowning deaths of female aphids which were still producing young. A more useful value to examine was therefore the mean young per day, since this reduces the influenceof sudden deaths. A plot of the mean young per day gs days after reaching the adult stage is shown in Figure 15. Dashed lines in- dicate means for which less than 10 aphids were available for calculations. Production of young by individual aphids appeared to follow a pattern in which young were born at a fluctuating rate. The plots of mean young per day also show this trend. This may be an unnatural effect due to MEAN-YOUNGIDAY 2.0« 1.5‘ ' 1.04 0.5‘ 0.0‘ 2.0 d 1 ...‘id 1 .O'l 0.!5'l 87 TREATMENT lV-23 C W‘WU T I r1 I r v 2 4 3 8 10 12 14 16 18 20 22 24 26 28 3O TREATMENT III-'17 C I‘\ i 0.0 2.0‘ 1 .5. 1.03 0.5‘ '2 ti ‘6 ' 8 '1'0t1'2'1'4'1r611'8'2'0'2'2'24'26'2'8'30 TREATMENT u-1o c 0.0 V V 1 V t V V V i r V I I 8 ' 8 1011'2'1'4'1'6r1t8 20 22 24 26 28 80 DAYS AFTER MOLT To ADULT INSTAR FIG.15.—Fecundity of apterous viviparous Illinoia pepperi on excised blueberry leaf discs at 3 temperatures. 88 the observation scheme, or possibly a physiological system involving timing of births according to light dark periods, and the temperature. DISCUSSION The most intereSting biological feature discovered in this experiment was that I.pepperi raised at 10°C re- quired the greatest number of degree days to complete a given amount of development, while aphids at 5°C required the fewest. Normally, it is expected that within a certain range, the amount of degree days needed to complete a fixed amount of development should be equal at any temperature. This relationship breaks down outside the acceptable range, where extreme temperatures adversely affect enzyme reaction and inactivate or denature proteins. Also, on the whole organism level, desiccation progressively increases at highers temperatures. Previous research indicates that treatments at the highest and lowest temperatures would exhibit lower developmental rates in aphids, thus requiring more degree days per stage or event. The experimental data for I. pepperi fit this scenario at the higher temperature treatments. Development was never completed at these tem- peratures. However, the lowest temperature treatment also did not show a lowered developmental rate: it was actually greater than all the other temperatures. Even more atypical was the very sl w developmental rate found for the aphids kept at 10°C. These aphids required 89 significantly more degree days to develop than aphids raised at the temperatures above or below 10°C. Figure 16 compares the developmental rates, in terms of degree days per stage, for the six treatments. The physiology of the host plant may partially explain the effects observed in this experiment. Many different physiological processes are taking place within living blueberry leaf tissue. Plant tissues normally begin a "hardening off" process when triggered by environmental factors such as water stress, changing photoperiods, and changes in temperature. This process is normally gradual, and in blueberry the leaves become tough, leathery, and dark reddish or purple in color when the process is complete. There is a build up of tannins and other cell products, and such tissues are generally less suitable to insects, slowing their development. Plant tissues kept above this temperature would continue to develop and produce photosynthetic products in a normal manner, and remain suitable for insect development. Normally growing plant tissues suddenly exposed to very low temperatures would be cued to start the hardening off process, but because of the extremely slow rates of enzymatic reaction at the low temperature, hardening off occurs 3251 slowing; the tissue may actually remain very acceptable in terms of changes in texture, nutritional status, and suitability to insects 90 1C") 5 (26°C) 9K) 6 (29°C) ‘3 05 80‘ u n] m 1 ‘l m 10 c) 0 1C p. 00 a 80 U] EL 00 i 50- C: "J . NH 0: 8 40- CD 2 d ‘K “J :2 43(3' .1 I I r U I ~ll Ill l\/ FHREE FIEJ’. STAGE FIG.16.-Mean degree days per stage of Illinois pepperi on excised leaf discs. Tregtment temperatures: (1) 5°C; (2) 10°C; (3) 17°C; (4) 23°C; (5) 26 c; (6) 29°C. 91 feeding upon it. Degradation of cell components would also be very slow at the lower temperatures; at the warm temperatures the breakdown products within plant tissues may affect the food quality of the tissues. The apparently abberant experimental results can be supported using the cell physiology explanations outlined above. At 5°C in treatmentlu the blueberry leaf tissue ‘was at a sufficiently low temperature to eliminate de- gradation of cell contents, but too cold to allow normal hardening off processes to render the leaf less suitable to aphids. These 5°C leaf discs may represent the best in terms of aphid nutrition. Leaf discs at 10°C were actively hardening off and becoming unfit for aphid growth faster than the leaf discs at other temperatures. Leaf discs at 170 and 23°C were not hardening off; they actually grew in diameter while floating on the media. However, due to more waste products and degradation at the higher temperatures. they might actually have been slightly less suitable for growth of aphids. There is a possibility that aphid physiology may have a significant relationship to the lower developmental rate at 10°C. Further experiments using artificial diets would eliminate the variability due to leaf disc quality and resolve this situation. Also similar experiments using leaf discs but changing discs at very short intervals may reveal the reason for the unexpected results at 10°C 92 (more frequent handling of aphids may lead to other problems, if such an experiment were undertaken). NOTES ON BEHAVIOR AND MORPHOLOGY OF I. PEPPERI Behavior -- Through the course of the laboratory experiments constant observation of individual I; pepperi provided some information on the behavior and general appearance of the different stages. I; pepperi is a relatively fast aphid when walking, allowing them to travel significant distances. However, when feeding they are very sessile. This aphid prefers to place its stylets into or as close to leaf veins as possible. All instars remain for a long period of time in the feeding position unless provoked in some manner to move away. Repeated attempts to disturb them with a fine brush are often necessary to cause them to remove their stylets from a leaf. As noted in the section on field studies, there apparently is no alarm.pheromone communication between colony members of I. peppéri. Morpholggy -- A11 aphids in the laboratory studies were apterous viviparous females. The eyes of future progeny become pigmented days before they are born, and can be seen through the cuticle of adult females. Up to 3 embryos could be seen at one time in this manner. The adult stage can be separated from the earlier instars very easily by body size and shape. Adult apterous viviparous I. pepperi have a somewhat flattened dorsum, with depressions and a 93 ridge towards the lateral edge of this surface (see Figure 17). The antennae of older individuals began to curl slightly at the tip. The entire body is covered with. a whitish waxy coating, powdery in appearance. This is formed shortly after ecdysis, and slowly wears off or dissipates in some manner during the instar. In old adults this surface coating is completely absent, giving the aphid a very shiny cuticle. GENERAL DISCUSSION The biology of Illinoia pepperi and the spread of Blueberry Shoestring Virus disease can now be more easily related, and the information to be sought in future research identified. The slow in-row spread pattern of BBSSV is likely due to the rather sessile feeding behavior of all stages of this aphid, and the rather low percentage of winged aphids produced under normal conditions. Analysis of disease incidence has led to the conclusion that the source of inoculum for transmission was within field and not due to constant re-introduction from other sources (Lesney et. al. 1978). I. pepperi are found almost exclusively within blueberry fields, even when acceptable alternate hosts are present in surrounding areas; there 94 FIG.17.-Apterous viviparous (A) and alate viviparous (B) forms of Illinoia pepperi (MacG.). Approximately 20X. 95 is apparently little movement out of or into fields by aphids. These two findings support each other. It is interesting that both BBSSV and I. pepperi have very limited host ranges. The disease is exclusive to blue- berry, and the aphid has few alternate hosts. This suggests a very close ecological relationship between blueberry, BBSSV and I. pepperi. Control strategies involving the disruption of this relationship may only have to impact on one specific feature in order to be effective. Re- sistance of certain cultivars to BBSSV or aphids is known and may be sufficient to significantly reduce transmission of the disease. Before the value of cultivar resistance or other control tactics can be accurately measured, the remaining details of aphid biology, behavior and disease transmission need to be determined. Further refinements of the aphid density estimation techniques are needed. Aphid behavior within bushes in fields needs to be analyzed to determine the factors which induce movement and the directions and distance traveled. Further transmission studies will be necessary to generate an accurate estimation of vector efficiency. With such a value for BBSSV and I. pepperi, aphid populations within fields could be related to a possibility of disease spread. From such information, and economic injury level for aphid populations could be established and used for careful planning of controls. 96 Much of the information generated in this study has potential use in the development of models or simulations of the blueberry-BBSSV-aphid relationship. A preliminary model dealing with aphid population dynamics and movement has been constructed by Cameron et. al. (unpublished report 1981). Future additions to this model may someday produce a management tool for the control of BBSSV disease, once other critical components are develOped. The relationship between populations of I. pepperi, plant or field conditions and vector potential of the aphids at any moment would have to be generated and compared to an economic injury level. Plainly, much information remains to be found before such a model could be adequately constructed and verified. APPENDIX 1 APPENDIX 1 Record of Deposition of Voucher Specimens* The specimens listed on the following sheet(s) have been deposited in the named museum(s) as samples of those species or other taxa which were used in this research. Voucher recognition labels bearing the Voucher No. have been attached or included in fluid-preserved specimens. Voucher No.: '1’; 'A Title of thesis or dissertation (or other research projects): BIOLOGY OF ILLINOIA PEPPERI (MacG.), THE BLUEBERRY APHID, AND ITS RELATION TO BLUEBERRY SHOESTRING VIRUS DISEASE IN WESTERN MICHIGAN Museum(s) where deposited and abbreviations for table on following sheets: Entomology Museum, Michigan State University (MSU) Other Museums: none abbreviations: AL - alate viviparous AP - apterous viviparous 0V - oviparous V} corymbosum - Vaccinium.co;ymbosum Linn. cult. = cultivar Additional specimens are in Investigator's Name (9) (typed) the collection of M. Whalon, Date February 8, 1282 *Reference: Yoshimoto, C. M. 1978. Voucher Specimens for Entomology in Nbrth America. Bull. Entomol. Soc. Amer. 24:141-42. Deposit as follows: Original: Include as Appendix 1 in ribbon copy of thesis or dissertation. Copies: Included as Appendix 1 in copies of thesis or dissertation. Museum(s) files. Research project files. This form is available from and the Voucher No. is assigned by the Curator, Michigan State University Entomology Museum. 97 98 APPENDIX 1.1 Voucher Specimen Data 1 of 3 Pages Page mum: Wm \ euwmuo>esa oumum coquowx man a“ uwmoeop HOuoimu _~mma .aum m 606a How newswooem moaned o>ono osu po>wooom Q1 4»: .oz Hono=o> AaaasuV seesaw .4 nfisum Amvmamz n.uoumwaumo>cn Aeummmooo: ma muoocm Hmaowueppm 002v am: am: am: flm do Mama Hoeaooon n Ham cameo .oaaa>auoaoou .Hz_..ou damage nonnam .m .Hou .homuow._hwwso asmoeawuoo .> no awed nonaouon m Hmu madam .0HHH>muoaooo .Hz ..ou «anuuo A.uaazv “Canada aaoaaHHH A.oomxv auaaada aaoaaaaH A.ouuzv snowmom,oaoawaam Museum where depos- ited Other Adults 0' Adults 9 Pupae Nymphs Larvae Eggs pouamoeop paw pom: no pouooaaoo newswooem How sump Hanna coxmu uozuo no mofiooam "mo Monasz 99 APPENDIX 1.1 Voucher Specimen Data Pages _§__ of _2_ Page some at soumuso New“ nae m dude huwmpm>aca oumum :mwficowz may aw uamoemp one: HoEOucm now mcoEHowam woumfia o>onm osu po>wooox sun .02 uo£o=o> 1N»! Aadassv nonmam .< aezum AmVoEmz m.HOumwfiumo>:H Axummmwooa we muoonm Hmcoauwppm mmav 3m: am: am: A .42! y Hoanam .m .HHou .homuon. .wH:o abnoamNuoo .> no Hmma hash «N m a a «n wedge .u>aHo and: .HS ..oo mamuuo soamam .m .Haoo .homuoh. hmwoo Eamonahuoo .> no amaa 06ama< «a < em paoaw .w>wao “no: .Hz ..ou wsmuuo madman .m .HHou .mnwaaoo. .mwso asmonehuoo .> do Hmma unswsd q 4 en madam o>aao umoa .Hz ..oo msmuuo _ A.oomzv Huumaum.nfioaHHHH A.ooazv auoamda‘aaoaaHHH A.oua:v endgame afloaaaaH Museum where depos- ited Other Pupae Nymphs Adults 0' Adults 9 Larvae Eggs pouwmoeop pom pom: no pouooaaoo mooefiomam now dump Hanna aoxmu amnuo no mowowem “mo sonsnz 100 APPENDIX 1.1 Voucher Specimen Data Pages 3 of 3 Page 318m...” xummuo>wca oumum cmwwcowz ecu cw nemceop uteri—DU $3 :25 w 38 a. 404V .E—mmzz CFC “cu so» measuooam poumwg o>oem ozu pm>wooox 4M... an... .oz uososc> Amwazuv uoamam .< afisnm Amvosoz m.u0umuwumo>cm Azummwwooc we muoocm Hmcofiuuppm 003v ’4 uuwuom\uoomam .Haoo .homuoh. .mHDU abmonahuoo .> no Hmma moon q Aq4 : e .n a 2 a u c e O o 5 a to south: 1979 - Clear Fleld 1980 - 2 year plants set out _— Rows of Blueberrles ...—*- Ditch ’% Trees “ Shrubs m -pan trap FIG.19.-Field If 393, Park Township, Ottawa Co., Mi. Wesley Waldron, owner . .uoan .moabwea a03< 2“: ..oo 96qu .aaeaaaoe aoeaaam spam .5 e camamuu.o~.uam 103 no: can... a 9:233 .093. a .0 So :28: s a. s 22“. “262 339033 3:52.30 T antenna... .o 3.063 3522 >233; I' 339033 possEoo a .3303... 2 - 3.3:. 936» atone—.3 03.2: h 0.5.“. — — U331 Open a.“ 105 FIELD 281 Blueberry plantlng 3.2.325 .stoaaeac house Hayes St. K c o t 0 e .w M .w t n e D o "“3 '- ditch 5.". . ...-e. m - pan trap - "908 .o>< 5'0 ...v. EN at It“. \ wig , 233a . .. 1b...“an 4.7.07, inn-“rs. $5.. Msmflmmu A .43...w..\....aw\n «An/...kamm - driveway .' , In} C v.14— ' , 51.4 FIG.22.--Field # 281, Polkton Township, Ottawa Co., Mi. Frank VenRoy, owner . APPENDIX 3 APPENDIX 3 1979 PAN TRAP DATA AND WEATHER INFORMATION weather data sources: temperatures; in-field hygrothermographs for fields 7, 54 and 281. Field 393 temperatures obtained from NOAA Monthly Summaries, Holland MI. recording station. rainfall; amounts for fields 393, 7 and 54 from Holland, MI. station. Amounts for field 281 taken from Nunica, MI. station. wind speed and direction; data recorded at Muskegon, MI. station were used for all fields. This was the closest station recording such information. 106 107 .ndé a.“ page as: $826 23.3: 03.5 so: 0330—030 euoumuv we use“. 5" caduceus paw: uaeuaseumn .enaa .~ norm: souu pounds-sous Aho~.on enemy shoe cannons m.a an N. as Nana an o N N o x ~.Ha an a. an mass nu a.aa an an as . ewes «N o o o a x m.aa «N ah.o me an 3631 an m.oa n. as is ones on a.na «a a. an sans a3 0 N m a x 1.33 so .a an as men” as “.41 ea we sh sans a” ~.na oN we we Nana as o o o o x a.o_ oN as am aa~a ma o.~a aa a. Na mmua «_ n.s «a me an mama «a a H o o x n.s an o. oh swan «a 6.0 am oa.o a. so chad as o o o o x A.ma nu aa.o as me . ands ca «.3 as mm.o o6 ma mass a. «.9 - s~.H as am amen o o o o o x a.oa as so an ones a n.». nu an a» macs n.a an an an «ad m o H o o x m.a ca 88 am maa . a.» a“ on an oaa n a.a AN ma Na and a o o o o x ~.a mm mm as mam a «can .0 mm am we mm. aaaa> aeoam .uaa . Hague 6.: an: a nu on» on couscous and can“: unseen .mmoe unusuaaasoo< .mmm was?“ 603-«adu- uonueoz voueuuoeee v.3 “Mean 39.3.: one: we eosuuwo noun. cam who." .NN canon. 108 .n.nyl nu vuonu va«D.ouou¢>i «sauna cauu Baum oustuoau uoouuov mo luau nu coauuouav v:«i.ua¢udslona .asmd .H zuuqx_souu concealsoou Abo~.on sunny ohcv Gena-no . o.n NH . 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H.a «N «0 NH «mnH bu o o H o x a.HH «H HH as aHnH ea ~.H oH mm «H mNmH as «can ll fl D am 3m "2 .3333 cam .vuaauuuoo .NN OHAIH ...—.9! a.“ noun- vaw: «@325 393.. 3.3 30.5 033030 000.33 «0 on: a.“ 8.33qu v5: 339:: .22 .H 5.8: as; 32358. 2%.: 8:: .3. can 109 3 :5 mm 8 88 2 H.HH o o o o o x a... .HH cm M: £2 3 H.HH an 3 8 . 8S 3 3: an :6 an S 22 .HH 5:: HH .3 H... 83 2 o o o o o a n; 2 3 2 83 2 9a 8 g 2 33 HH finH 9... SH 8 E 83 2 o o o o o x H23 D 35 8 mm Hmmu o ....n «H S H: a: o HHH «H S no 38 H H o o o o u a; 8 26 an S 83 a o; 3 $6 8 2 88 n ma 2 3 5 33 c 9o 2 on 2 . 88 n o o o H o a 3.. 3 86 S on 83 u ‘ ....m 3 no 2 £2 H .34 .2: on 35 2 2 32 8 o o o o o x 9a. 2 on ma :2 on N; S 2 S 8.; 3 ma an 25 3 E. HEN 3 NH 3 on 3 ”SN 3 o o H H o x 1... on H. mm 3 $2 8 ~12 «a 25 2 3 $2 2 92 2 3 S 3.2 a o o o o o x as ca 25 8 mm 32 2 9n 2 Hm .3 3.2 «H .3... u an .5 m2 32 33> 25% £3 . Hoes 3x .3. a 3 «8 on 8 £8: flOfluIOOA at five—"3 Ing “Uh. dfiflulgonv‘ 63533 . NH .23. 110 5.9.. 3 .62.- HHHHH: undue». £33 3.3 38G c.3030 uuouuov mo .63 .5 90.300qu ...—«3 undone-u.— .aRH .H :93: 693 wounds—Hood Couén 0:3 .53 03:81 n... 2 8 HH. 2:” «H .2: «H an ..m . 82 HH o o H o o u fl: 3 .... i 23 S 92 «H an $ 38 a 06 8 3 H... 23 o «.2 an an 8 23 H o o o o o x 3: on S 2 32 o a... ...H . NH 8 32 n H; 8 mm i 82 c o o o o o n H; mm mm 2 .23 n . 3: «a 2 2 8.; N «.2 2 H... mm 3.; H as a; S 3 8 ~qu Hn a.» 2 .H. an H... 32 8 o o o o o a Q: 2 25 3 9H 3mm 3 ”.... 2 H3. S 2 2mm 2 m; 2 Ho NB 2.2 R a... 2 S H: 3% 3 c o o o o u H.» on ..n 2 «SH .3 m.o ..N 86 3 mo 2% «a ...... 2 SH 3 2 Ham 2 a... HH on HH 3: 2 o o o o o a 3H 2 $6 3 fl HHHm Ha a; 2 2H an $ 88 3 o o c o o x n... HH H. mm a Son 2 a... R 85 on E 38 2 .94 u um 3 Hz 132 33> 2.25 :3: .AHo-umiwwH .8: 2H3 3&8 non Human aoauoooa cum 233 03—25 .mu. «wands-53¢ .— 625.353 . «N 0.33. lll .n.n.l nH voonu va«3.¢u¢u¢>i «Auuoa can» scum oostuoHo uoouwov Ho uaou cu coauuouuv vcwahuunlnuonna .msmd .H noun: aouu vmuuaaasoun Amo~.on ooupv chad oouucna . a.n Nu cc mm mmuu «N n.o «a co mm Howu an o o o o o u ...... 2 mm 8 . 2: 2 o.o on mm on . anN mH o o o o o x H.a an en on quN ha e.oH em on mm QOHN 0H n.o cu mo ma mucm n” o o o o o x n.m «N co mm Hcou «a o.n aH . um om «cow an o.n «N on no mo¢H Na oé mm on ca 22 HH 0 o o o H x m.c HN mm ¢n ommH an n.m as oo om «umH o n.e 5H me we oemH o o o c o o x n.n an H.» an 23 u o.m an an 2 . HEH o H.o an an ox mnnH n «.2 3 3.0 mm K 33 c o o o o o x o.c OH we Hm enhH n m.¢ «n «0.0 no aw ocsH « m.oH an, a an we omcH H hash x o.HH nn mn.H an no eooH an ad 3 Haé Ho fl. 30H as x n.s HH No.o on ma oHoH on H.o «N co us NmmH nu m.HH 0H He as aemH on a.» oH mm as mmmH mu aqua n a... .5 xx 32 33> 33w .uHa .385 an. an: a 3 as. on 8 58: gall nos: .22: a-vouflsflog .n vaHm .auuuufiunum Hogan») vuuuaoouoo van “Hummun «HOGHHHH ouaa< mo amnuumo many can asaa .nN CHAdfi 112 5.9! a.“ coon- vufi. «mung. «5.3a 3.3 393 033—030 noon»... no 33 a.“ 8.300an 255 33160:: .aHmH .H noun: Bonn wound—.500- AMouén once on... .3qu 2 id mm no moon 2 H.HH o o o o o x o.e «H mH HH mmHH oH H.HH mm mm HH . ooHH nH H.HH Hm HH.o Hm cH HnHH «H H.HH HH Hm Ho omHH HH o o o o o a n.H HH on mH HoaH HH H.H He ea mH HHHH HH H.HH on oH..H Ho mm 33 S o o o o o x H.HH HH 86 co «m HmmH a H.n HH . an em HHHH o H.HH HH Ho Hm ooHH H o o o o o x m.H mo Hm.o on em mHHH o o.H oH He.c Ho Hm eHoH n m.m HH mm on mooH c o.m HH mm Hm . HHoH n o o o o o n H.o nH Ho.o «m H» HoOH H n.m Ho Ho HH mHnH H .ua< H.oH on HH.o no mm mHmH HH o o o o o x o.a HH on on HHmH an H.H Hm 03 mm owHH HH n.» Hm mH.o no mm HmHH oH H.H HH oq ow HHHH HH o o o o .H x H.H an H en Hm HHHH oH H.HH HH mH.o no HH HHHH nH H.HH HH «9 Ha HHHH «H o o o o A. x o.o OH HH.o Hm Hm HHHH HH o.n HH 03 Ha mmHH HH HHan u a... am «am . 32 33> 3un £3 . Hog—H 3: an: 8 .3 8 8 fine: 8:38 5H :23: .333 lfloH. $83333 60:33:00 .3 03.9 113 5.9- a.“ coon- vaa: ouuuobq “sauna 3.3 aouu c.3030 uooumov Ho .33 H: 5333.... can! young-nu.— .auaa ..n :93: Baum @3335qu Abouén «one .58. cannon: @— NH 3 2 do an on an so an «N 2 3 an «N 3 S 3 on .HN 3 3 3 o— 3 mm 0 mm 3 Hz 32 33$ .3on .uwn cog-ace an.— 5055 O O O I O O O O O F‘s-i Flt—t 0000.000... o-O GMQQQQO‘NO‘MQMO‘ONG—O—IO\NV\\DQNQM C . «0...: 3: an! u 3 can on co «m HHHH HH Hm Hm . 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Hoaa ca m.e mu mm.o cm as enaa m «.9 «N ¢~.H oo am mofifi m o o o o x a.o~ mg no mm mmofi u m.m m“ “m cm qqofi o m.n mm mm mm afiofi m o o o o x w.m an em «w Nwm e ~.m «N we om mmm n m.c am oq on “Na N o o o o x ~.a mu me on mom a «can 0 mm 3m m2 \mmm ugua> umomw .uga .aauuum sax was many common ”we gang: coauuuoa can nun“: nonunu .mmoa ovuuuaaaauo< .< cm vamfim .uuwuouunuo nonunoa counwuoouu can «nonmwm muosaHHH ouuH< mo nosuuno many can anan .QN vanes 115 .néé a« noun. an“: 3302. 3qu: 0?.5 395 033—030 33qu no «no» a.“ noun-003v v53 unauguuua .33 J no.3: scum amazon—53¢ Couén 0:5 226 oouuund . m.n NN -om em ncNN «N as 2 .2 3 32. ca 0 o o o H N c.c nN me Nw mHNN aa o6 on .3 mm mm: 3 o o H o o x ~.m mm mm Nu NodN he <.o~ an co Nm mqfiN on m.c «N «c on ofifiN mm o o o o o x m.a NN we cm mmoN «A o.m ma No on mmoN nu o.m NN No hm ¢am~ NH m.¢ mN No om Noma ma 0 o o o H x m.o ~N on us QNmH ca m.m mN on us mmm~ a «.0 Na mm cm Osmu m o o o o o x m.m nN N< mm H¢mH h o.n wN oq mm mama o ~.m on oq oh mama m e.N~ do nw.o on on owma q o o o o o x 0.0 Ca Nn cm mnna n m.m Nm No.0 mm on mNhH N n.o~ mm H he no maog A Adan o o o o x m.- mm mm.H Nm no owed On m.m co Hm.o on as Good aN o o o o x n.~ a“ No.0 mm oh Nmod 0N ~.m NN Nm mm hood «N o o o o x Q: 3 co an 2.3 on N.N 0H on mm menu nN «can 0 mm 5 uz 32 :35 Bum—w £3 .335 5: .8: 99:. «8&3 N3 58: ..IF .3333 cam A253 00:05 .mmoe «wounds—nuni .vmacaucou . «N $.33. 116 .3.928 nu vvonn nag: omnuo>u «canon oauu Baum ooaaxooau compact mo oaou nu nouuufiuav vd«3_uauuH:QQMA .asaa .H noun: aouu vouodaaboua AmoN.mn canny uhuv ooumunu hm ~.- ed HH.o «a do Noon o o o o o.e «N on on neon cu ~.H~ an me we omen n" N.e~ unv _q~.o um no moon ed ~.c~ flu co he mwmu n" o o o o n.~ ma mq Nb mo¢~ «A m.a do «e oh «emu Ad ~.m_ on o~.~ we on NNmN o_ o o o o H.HH NH acme do em ammN a a.n aN «a mu mmmu m m.HH - me an mumm n o o o o a.“ mo mm.o mm om mmnu o m.“ cm sq.o co an umuu m m.w ¢~ mm «a «NNN e o.m «N am om “wom n o o o o ~.m nu mo.o mm om oocm N m.» «o No as omom a .u:< «.od on m¢.o no «u doeN an o o o o o.a “a mu «m cmmw on N.“ _n mm «m Hmmu a~ m.» an mfi.o co mm amen a~ «.5 d~ mm «m NOQN «N o o o o H.m on a an on fimcu ow ~.n~ NN mH.o no «u deem nu m.n~ mg “5 mm Humw «a o o o o o.o cu mH.o no mm mmmN nu o.n «N on mm omNN «a bean 0 mm mm Immw zz uuua> amonm «mmmx.n«ooum am: an: mama ummuon mwn nude: acqunuoa dam aqua: nosuaH mmma navy-Haaauod .voanuunoo .eN «Hana 117 .:.n.a aw anon. cues owauo>i “sauce «spa scum onwaxooau ouuuwov mo mama ad nowuuouue wag: unnuaauuan .anma .H noun: Baum vauuaaaauoo AmoN.mn macaw shoe ooumunu a.» «N am ow oNNm NN «.oN NN mm NN . NNNN NN o o o o o x N.NN «N o« NN NNNN oN m.o~ «N N« No mon a «.o No N« No «mom a n.NN mm Nm «« NNom N o o o o o x N.oN on no mN omen o N.« NN " mm NN Ndom n N.N No on NN Nana « o o o o o x N.N mm Nn «N «own N N.oN NN «o NN «mmm N N.o_ mg «0 Na comm N .uaom «.N «N no «N m««m Am a.» «N a No 2. om«m an o o o o o n n.NN NN oN.o no mN NNNN NN N.n «N Nm.o No NN comm NN N.N oN No «« NNNN NN m.« mN m« «N NNNN «N o o o o o x N.» «N Na No NNNN NN a.m «N No.o an oN «on «N «.N «N NN.N «« mN o«NN NN m.m NN om NN «oNN NN o o o o o u M; 2 $6 an 8 22 NN N.N oN NN.N No NN ««_N oN o o o o o x m.« S H. mm 3 38 2 m.« NN mm.o No NN Naom NH .u:< 0 mm 3m n2 :2 uuo«> «moan .uNn .Nwmuum ca: an: «Nae oummwa Nun nmmpz coauuuog cum wads uuzuaH .mmoa ovouodaauuud A .«uaaNuaou .«N «Nana 118 .£.a.a Ga Oummm wafia mmmum>m “sauce wsuu aoum mmH3¥UOHo mmouwmv we mama a“ :oauomuav Oa«3_ucmuH=mmmn .mNaH .H noun: scum OmumHaasoom ANON.Om mummy mNmO omuwmnm O.N mm O« NN N«nH «N O O O O x N.HH mm O« OO HNmH ON N.HH mm on NN «OmH NN O O O O x O.HH NN O0.0 «O NO ON«H HN 0.0H OH H «O ON «««H ON H.nH NH N« «O HH«H OH N O O O x H.HH OO 9 mm «N mOmH OH N.«H ON u OO ON NmmH NH N.mH ON OO OO «NmH OH O O O H x N.OH ON OO OO OONH mH O.NH OH NO NO o«NH «H m.N NH O« ON NHNH OH O O O O x m.N mm Nm NN «mHH NH m.o mN Oo.o N« we HNHH HH O O O O x N.nH nN O0.0 on NN HmHH OH m.« OH OH.O «O «N nNHH O N.O NN O0.0 no mO «OOH O O O O O x ¢.OH OH NO ON OmOH N m.O OH on OO «NOH O O.N mm n0.0 on ON HOO n O O O O x 0.0 ON H Hm mO NOO « H.O «N On NO Nmm O O.« HN N« ON mom N O O O O x N.m ON O0.0 On OO mOO H oaafi 0 mm 3 mz 32 33> Baum £3 .3895 5: an: 99% «9&3 man 58: nouuauog Gum AOGHS mmnuaH.IdmmmmlwwoumH583004 .HON OHmNm .muuumwumum umnuwms Omumauommw vam Npmnmun «HocfiHHH mumH< mo munuuwo amua cum aNmH .mN mHan 119 .s.a.a GH vmomm OGNS mOme>m "canon onuu Baum mmHaxUOHo mmouwwv mo mama aw nowuuwuav Odds uawuHamum A .ONOH .H noun: Baum vmumaaabuum AmoN.OO wmmnv mmmu mmummam 0.0 NN OO OO OOON HN 0.0 NN O« OO ONON ON O O O.« ON O« OO OONN OH 0.0 On O« HO ONNN OH O O H.O mm OO OO ««NN NH «.OH «O OO NO «HNN OH 0.0 «N 9 OO OO NOHN OH O O 0.0 NN . OO OO N«HN «H 0.0 OH «O OO OOHN OH 0.0 NN OO HO OOON NH O.« ON NO OO ONON HH O H 0.0 HN OO NN OOOH OH 0.0 ON HO «O HOOH O O.« NH OO «O NNOH O O O 0.0 ON O« NO OOOH N 0.0 ON O« HO OOOH O H.O «O N« ON ««OH O «.NH HO N0.0 OO ON ONOH « O O 0.0 OH 8 HO OO «ONH O 0.0 NO «O ON NONH N 0.0H Om N0.0 NO NO «ONH H NHah O O.HH Om N«.O OO NN HHNH Om 0.0 OO O0.0 OO ON OOOH ON O O.N HH O0.0 OO HN NOOH ON H.O NN NO «O ONOH NN O O.HH OH OO ON OOOH ON N.N OH O« OO OOOH ON «can 0 mm sz uHmw> Ommmm .uHO .nHuoum aaz_xmz mama muwwwnxwma nude: :owuuuoa cam n vafis mmsuaH .mfimy «OmumHaasuu< .OwaaHucou .ON manna .:.a.a cH woman Oafis mwuuo>m «sync: osuu aoum mafiaxoOHu mmuuwmv «0 «do» nu souuouuwu OaH3.u=uuH:mmmn .ONOH .H noun: Baum woumHsaauuu AmoN.OO mmmnv mzmv mmuwmnm 120 H.HH OH OH.O NO HO OOHO NH O O O O O x O.« «N OO OO O«HO OH H.HH OO O« OO OOHO OH N.«H NO OH.O OO OO «HHO «H N.«H HN . a NO «O NOOO OH O O O O O x O.N OH O« NN ONOO NH 0.0 HO NO «N OOOO HH N.OH OO HO3H OO OO ONOO OH O O O O O x H.HH NH NO NO «OON O 0.0 ON «O ON OOON O O.HH NN «O «O NNON N O O O O O N O.N OO ON.O NO OO HOON O O.N ON ON.O NO OO HOON O 0.0 OH 8 HO «O ONON « 0.0 NN H OO NO «ONN O O O O O O x H.O ON O0.0 OO OO HONN N 0.0 «O NO NN OONN H .w=< «.OH OO O0.0 NO OO HONN HO O O O O O M 0.0 NH OO NO OOON OO N.N HO OO OO «OON ON 0.0 NO OH.O OO OO OOON ON N.N HN OO OO NOON NN O o O O O x H.O OO NO «O ONON ON N.OH NN NO «N NO«N ON 0.0H OH NO ON «O«N «N O O O O O N 0.0 ON O0.0 NO HO OO«N ON 3” 2 on 3 32 2 32. 0 mm 5 mz 32 33> 35% .35 458.8 5: mm: 29.” ammun— E 58: coauuuoa dam Ova“: monunH.IlmmmHIwOmUMHnaauu< .Omaawuaou .ON mHOmH 121 .:.a.a ca Omonm On“: mmmum>w “nukes oauu scum mmwsxuOHu mmmuwmv mo mama ad aoauomuuv Os“? uamqumomn .ONOH .H noananum Omumasaboom omaN.OO mmwnv mOmO mmuwmam 0.0 OH OO OO OOOO NH «.OH NH OO ON NNOO HH O O O O O x N.OH OH OO NN N«OO OH 0.0H OH O« HN OHOO O 0.0 HO N« OO NONO O O.NH OO «O «O HONO N O O O O O x N.OH OO "H OO NO OONO O O.« OH OO HO NNNO O H.N NO OO NN NOOO « O O O O O x H.N OO NO OO OOOO O 0.0H NN OO NO OOOO N N.OH OH OO OO NOOO H .ummm O.N OH HO «O OOOO HO O O O O O x 0.0 ON OO NO «OOO OO O.HH NN O0.0 OO ON OO«O ON 0.0 OH O0.0 NO NN OO«O ON O.N OH HO «O OO«O NN O.« OH O« ON «H«O ON O O O O O x N.O ON NO OO OOOO ON 0.0 «N HN.O OO ON OOOO «N «.O OH ON.O OO ON N«OO ON 0.0 HH OO ON OOOO NN O O O O O x 0.0 OH OH.H OO HO ONNO HN O.N OH HO NN O«NO ON O O O O O x O.« HH «O ON ONNO OH mé Z 86 S 2 .32 m: .92 O OO 3m Oz 32 ”56.; H.003... .HHO .Ofioaum in: nu: EGO mafia Nun nuaoum nowumuoa dam Ovaas mmnoaH.Idmmmmlmvmustauuod .vmanwuuoo .ON oHan BIBLIOGRAPHY BIBLIOGRAPHY Cameron, P., B. Foster, B. Kriegel and F. Petitt. 1981. A Simulation Model of Blueberry Aphid Population Dynamics and Movement. Prepared for Systems Science 843, June 8, 1981. Michigan State University, East Lansing, MI. 28pp. Clark, M.F. and A.N. Adams. 1977. Characteristics of the Microplate Method of Enzyme-Linked Immunosorbent Assay for the Detection of Plant Viruses. J. Gen. Virology 34: 475-484. Coon, B.F. 1959. Aphid POpulations on Oats Grown in Various Nutrient Solutions. J. Econ. Entomol. 52: 624—626. Elsner, E.A. and M.E. Whalon. 1980. Blueberry Aphids and Blueberry Shoestring Virus Disease in western Michigan, p. 175-196 In J.N. Moore (ed.), Proceedings of 4th North American Blueberry Research WOrkers Conference, Oct. 16-18, 1979, Fayetteville, Arkansas. 396pp. Gilbert, N. and A.P. Gutierrez. 1973. A Plant-Aphid- Parasite Relationship. J. An. Ecol. 42: 323-340. Gilbert, N., A.P. Gutierrez, B.D. Frazer and R.E. Jones. 1976. Ecological Relationships. W.H. 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