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Ill!IlllllllzlllljllllllllljlljlllllllIllllllljllll This is to certify that the thesis entitled IMPACT OF REDHEADED PINE SAWFLY, NEODIPRION LECONTEI (FITCH), 0N YOUNG RED PINE PLANTATIONS presented by Robert Dean Averill has been accepted towards fulfillment of the requirements for Ph.D degepin Forestry Major professor Date November 14, 1977 0—7 639 IMPACT OF REDHEADED PINE SANFLY, NEODIPRION LECONTEI (FITCH), ON YOUNG RED PINE PLANTATIONS By Robert Dean Averill A DISSERTATION Submitted to Michigan State University in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY Department of Forestry 1977 ABSTRACT IMPACT OF REDHEADED PINE SANFLY, NEODIPRION LECONTEI (FITCH), ON YOUNG RED PINE PLANTATIONS By Robert Dean Averill The concept of forest insect impact is presented utilizing the redheaded pine sawfly, a serious defoliator of young red pine trees 1 to 5 meters tall. Impact is defined as being composed of two components: (1) ecological--the cumulative net effects of the insect on the total forest site and areas off site, and (2) socio- economic--the value judgments and/or decision criteria established by management objectives. Impact is a dynamic variable, and a function both of change in the forest condition and of the criteria established for particular management objectives. Six intensive study plots ranging from k to l acre in size were established in the Manistee National Forest near Boon, Michigan. Each plot differed in soil, topography and vegetation. Additional red pine plantings in Lower and Upper Michigan, Wisconsin, New York, and Ontario, Canada, were censused for sawfly damage and site quality. Three site classes of resistance to sawfly were identified based on soil development and disturbance, competing vegetation in Robert Dean Averill the rooting zone of red pine, and suitability for red pine growth. Site resistance class I (SRC-I) was most resistant to physical change by the sawfly whereas SRC-III was most susceptible to change and SRC-II was intermediate to change induced by the sawfly. Sawfly egg cluster density was lowest on SRC-I and highest on SRC-III. Survival of larvae was significantly lower on SRC-I than the other two classes; survival was not significantly different between the other classes. Infested trees had egg clusters distributed as follows: terminal 8.6%, terminal and top whorl 36.l%, remainder of tree 63.9%. Tree height varied between 0.l3 and 4.89 m during the course of study. Trees shorter than 0.6 m were not attacked, and in attacked trees over 3.0 m all egg clusters were distributed in the terminal and upper. whorl. The sawfly preferred to oviposite on trees between 1.2 and 2.4 m tall. 0n better soils the sawfly ate more foliage than on poorer soils. Tree mortality occurs with a mean of 96.5% defolia- tion. Growth loss was related to tree height and terminal length. Terminal growth loss from sawfly was significantly different between classes but terminal defoliation was not. Tree survival was 68% on SRC-III lands prior to the sawfly outbreak. The sawfly caused 54% tree mortality during the study. 0n SRC-I and SRC-II lands the sawfly caused tree mortality of 2 and 4%, respectively. Egg parasitism was significant and the larval parasite, Exenterus amictorius (Panzer), was discovered for the first time on this sawfly and was the most significant larval parasite. Robert Dean Averill Impact models were developed showing the relationship of host vigor to both tree growth and sawfly dynamics by site resistance classes. Identifiable physical changes to multiple use management objectives were incorporated into the models to allow calculation of impact to each management objective and to determine if the overall impact is positive or negative. A risk rating guide was developed for use in the field to rate both proposed red pine planting sites and existing plantations to sawfly damage. Equations are presented for red pine growth and determination of future product yield of sawfly attacked trees. Dedicated to Clarence Campbell Averill ii ACKNOWLEDGMENTS The opportunity for this study was provided through the USDA Forest Service, Forest Insect and Disease Management Field Office located in St. Paul, Minnesota. The assistance of their staff and summer assistants was valuable in making the study possible. Appreciation is extended to the personnel of the Manistee National Forest, Canadian Forestry Service, Forest Entomologists in Wisconsin and Michigan, and the private landowners who provided locations on which this study is based. My sincerest appreciation is extended to Dr. Louis Wilson, who has guided and inspired my efforts throughout my graduate program. The invaluable aid of my committee members, Dr. Donald White, Dr. Victor Rudolph, Dr. Stanley Wellso, and Dr. Richard Fowler, in providing helpful suggestions and constructive criticism is appreciated. Finally, special thanks to my wife, Sue, for her encourage— ment and patience during this period of graduate study. TABLE OF CONTENTS LIST OF TABLES LIST OF FIGURES INTRODUCTION Objectives Study Areas . . Definition and Concept of Impact Components of Sawfly Impact . THE INSECT Life History of the Sawfly . Distribution of the Sawfly by ”Site Classes" Distribution of the Sawfly within Trees . Consumption of Foliage by the Sawfly . Factors Limiting the Sawfly . . THE TREE Tree and Stand Dynamics . Damage Effects from Defoliation Competition . . . . THE SITE Soil Structure and pH . Precipitation DISCUSSION . Ecological Model of the Redheaded Pine Sawfly . Population Dynamics Model of the Sawfly Ecosystem Socio— —economic Model Summary RECOMMENDATIONS LITERATURE CITED . APPENDIX iv Page Table l0. ll. 12. 13. LIST OF TABLES Location and tree data of redheaded pine sawfly study areas in Michigan, at the peak of defoliation (spring 1971) . . . . . . . . . . . . . Location of additional redheaded pine sawfly plots examined in red pine plantations in eastern North America . . Number of sawfly egg clusters and larval colonies by plots and years . . . . . . Sawfly egg population for each study plot by site classes at the peak of the outbreak (l97l) Sawfly larval population for each study plot by site class at the peak of the outbreak (l97l) . . . . Partial life tables for the redheaded pine sawfly. in the Boon Tower Plantation in l972 and 1973 Partial life table for the redheaded pine sawfly during the cocoon stage in Anderson Plantation in l972 Life table of red pine trees in the Anderson Plantation plots combined . . Mean apical and whole tree defoliation by year in all study plots in Michigan . . . . . . . Red pine mortality during the sawfly outbreak by study plots in Michigan . . Mean tree heights per each study plot by site classes at pre- and post-outbreak periods . . . . Site parameters of redheaded pine sawfly infestations within plots examined in North America Solum characteristics for plot Al, SC-I (non-attacked) and SC-III (severely attacked) areas Page 20 23 23 34 35 46 49 50 54 62 64 l'hh. Table 14. 15. I6. Solum characteristics for plot A3, SC-I (non-attacked) or SC-III (severely attacked) areas . . . . Future product potential of red pine in study plots and by site class resistance . . . . . . Future product potential prediction statistics for red pine attacked by redheaded pine sawfly vi Page 66 TOT 102 Figure l. 2. 10. 11. 12. 13. 14. LIST OF FIGURES Sawfly infested areas Red pine plot A3 showing distribution pattern of trees defoliated by redheaded pine sawfly larvae in 1971 Red pine plot Al showing distribution pattern of trees defoliated by redheaded pine sawfly larvae in 1971 Red pine plot Cl showing distribution pattern of trees defoliated by redheaded pine sawfly larvae in 1971 Generalized model of impact from an insect Frequency of egg clusters for various locations on trees by tree size for plots A1 and A3 combined Percentage of egg clusters for upper whorl and for all lower whorls on various sized trees for plots Al and A3 combined . . . . . . . . Red pine foliage consumed by sawfly larvae on trees growing on different soil series . . Red pine tree height plotted over age for all study plots combined . Red pine heights plotted over years for each study area . . . . . . . Mean tree height plotted over years by site classes for plot A3 . . . . . . . . . . Relationship of leader defoliation to whole tree defoliation Red pine plot Bl showing mean tree heights, hardwood overstory, and trees attacked by sawflies, by rows in l972 . . . Sawfly populations and Palmer's Index values for the period 1935-1973 for the northeast and northwest regions of Michigan's Lower Peninsula vii Page 10 12 15 25 27 3O 39 41 43 51 56 72 Figure Page 15. Sawfly populations and Palmer' 5 Index values for the period 1935- 1973 for the west and east regions of Michigan' 5 Upper Peninsula . . . . . . 74 16. Relationship of mean Palmer's Index values to popula- tions of sawfly in Michigan by regions . . . . . . 76 17. Ecological model of the redheaded pine sawfly . . . . 81 18. Population dynamics model of the redheaded pine sawfly-- red pine ecosystem . . . . . . . . . . . . . 87 19. Socio—economic impact model of redheaded pine sawfly . . 91 20. Soil-moisture and tree growth relative to site resistance classes . . . . . . . . . . . . . 93 21. Risk rating guide for redheaded pine sawfly impact in red pine plantations . . . . . . . . . . . . 95 viii INTRODUCTION The redhead pine sawfly, Neodiprion lecontei (Fitch), is an important defoliator of young hard pines in eastern North America (Benjamin 1955) where it is particularly destructive to red pine, n- I?» an;- Pinus resinosa Ait., and jack pine, P, banksiana Lamb. It also feeds on eastern white pine, P, strobus L., Scotch pine, P, sylvestis L., Austrian pine, P, gigra_Arn., and to a lesser degree other species of pines planted in the vicinity of the primary hosts. This sawfly occurs in colonies of 100 or more insects and is a voracious feeder that readily strips small (1 to 5 m) trees of all or some of their foliage. Consequently, numerous trees may be killed or deformed during an outbreak. In the Lake States about 11.9 million acres are planted or seeded to red or jack pine, and approximately 44,000 acres of national forest plantations there have received chemical suppression measures in an attempt to manage this insect (Fowler 1973). The sawfly has destroyed thousands of acres of pine on state and private land where suppression measures have not been taken. Severe outbreaks did not occur until the advent of the widespread reforestation projects early in this century. Since then, the most notable Lake States outbreaks occurred in 1936-1940, 1946-1948, 1957-1960, and 1968—1973. Current emphasis on ecological matters and the benefit-cost analyses of forest protection require that the land managers have 1 better data on sawfly impact from which to draw their management decisions. This study was conducted to provide a data base for forest managers to enable them to better understand the impact of this sawfly in young red pine plantations. To accomplish this, data were recorded in red pine plantations infested with the sawfly during the 1968—1973 outbreak. Objectives The major objectives of this study are to: 1. identify and determine the important biological and ecological parameters that are important for the survival of the redheaded pine sawfly and its host; 2. develop a workable model of redheaded pine sawfly impact on red pine using these parameters; and 3. propose guidelines (based on impact data analyses) for managing this sawfly in red pine plantations. Study Areas The Manistee National Forest, Michigan, was undergoing an outbreak of the redheaded pine sawfly during the 1968—1973 infesta- tion at the time this research was begun. Three study areas (Table 1, Figure 1) in young red pine plantations were selected in the spring of 1971 and 1972, based on a survey of sawfly-infested areas (Millers 1971). All areas were open plantings on sandy soils with level to gently rolling topography. Edges were bordered by mixed TABLE 1.--Location and tree data of redheaded pine sawfly study areas in Michigan, at the peak of defoliation (spring 1971). Number Mean Mean Plot Location of Height Defoliation Trees (m) (%) Al . 22 N. 11 W., Sec. 34 NE 364 1.6 20.4 A2 . 22 N. 11 W., Sec. 34 NE 300 1.6 24.2 A3 . 22 N. 11 W., Sec. 27 SE 664 1.5 16.6 81 . 22 N. 11 W., Sec. 28 NE 349 1.4 12.5 C1 . 22 N. 11 W., Sec. 11 SW 594 0.7 1.5 C2 . 22 N. 11 W., Sec. 11 SW 763 0.6 1.5 Figure 1. Sawfly infested areas: (A) study plot A3 bracken fern pocket; (B) study plot A3 bracken fern pocket with dead trees (spring) after outbreak; (C) study plot Bl along hard- woods; (D) highly disturbed sandy site. hardwood stands or open fields. Trees were planted about 6 x 6 ft. apart. Ground cover consisted mostly of grasses and intermittent pockets of bracken fern, Pteridium aquilinum (L.) Kuhn, sweet-fern, Comptonia peregrina (L.) Coult., and bare soil (sand blows). Miscellaneous forbs, lichens, and sedges were a minor component. Six study plots, destined for intensive research, were established in the three plantations. Plot size varied from .25 to 1 acre. A I Iran-n. large private plantation called "Anderson" had three of the plots because Of diversity of terrain. These were designated A1, A2, and A3 (Table 1). A second planting on USDA Forest Service land, located near the Boon Fire Tower contained one plot designated Bl. The two additional plots were established in a Forest Service planta- tion planted by the Daughters of the American Revolution (DAR) and designated C1, and C2. Plots were set up specifically to include trees infested with sawflies, different terrain, and different ground cover. Three plot maps representing all types of field con- ditions encountered are depicted in Figures 2, 3, and 4. To broaden the scope and geographical area represented by this study, additionalplantations with a history of redheaded pine sawfly out- breaks were surveyed in August 1972. Plantations in Lower and Upper Michigan, Wisconsin, New York, and Ontario, Canada, were examined (Table 2). Plantation locations were provided by Forest Service and the appropriate State and Provincial forestry organizations. Examinations consisted of recording data on insect populations, diversity of terrain, and soil profiles. TABLE 2.--Location of additional redheaded pine sawfly plots examined in red pine plantations in eastern North America. State or . Province County Locat1on UNITED STATES MI Benzie Co. T. 27 N., R. 12 W., Sec. 16 NE MI Benzie Co. T. 28 N., R. 13 W., Sec. 35 SW MI Houghton Co. T. 47 N., R. 36 W., Sec. 31 NE MI Houghton Co. T. 27 N., R. 38 W., Sec. 26 MI Houghton Co. T. 47 N., R. 38 W., Sec. 26 EB MI Mackinac Co. T. 43 N., R. l W., Sec. 35 5% MI Mackinac Co. T. 41 N., R. 4 W., Sec. 14 MI Mackinac Co. T. 42 N., R. 4 W., Sec. 31 NW MI Mackinac Co. T. 43 N., R. 5 W., Sec. 3 NE MI Mackinac Co. T. 43 N., R. 3 W., Sec. 20 SW MI Mackinac Co. T. 43 N., R. 3 W., Sec. 20 NE MI Mackinac Co. T. 43 N., R. 3 W., Sec. 18 MI Wexford Co. T. 21 N., R. 12 W., Sec. 18 MI Wexford Co. T. 21 N., R. 11 W., Sec.'s 3,4,9, & 10 MI Wexford Co. T. 22 N., R. 11 W., Sec. 13 SE WI Menominee Co. T. 30 N , R. 16 E., Sec. 26 NW WI Menominee Co. T. 20 N., R. 16 E., Sec.'s 3,4,9, 8 10 NY St. Lawrence Co. Stockhom Township Block 33 NY St. Lawrence Co. near Canton NY St. Lawrence Co. south of Stockhom Center CANADA Ontario Simcoe Co. Vespra Twp. Concession 1 Lots 34 & 35 Ontario Simcoe Co. Flos Twp. Concession 2 Lots 26 & 27 Ontario Frontenac Co. 050 Twp. Concession 3 Lot 26 Ontario Frontenac Co. Hinchinbrooke Twp. Concession 5 Lot 9 Ontario Lanark Co. Bathurst Twp. Concession 4 Lot 16 Figure 2. Red pine plot A3 showing distribution pattern of trees defoliated by redheaded pine sawfly larvae in 1971. White = 0.9% defoliation; spot = 10-90% defoliation; black - 9l-lOO% defoliation. Delimited areas SC—I, SC—II, SC—III are site class divisions. Fern refers to bracken fern occupying SC—III class. SC—I and SC-III areas had grasses and forbs. Lower graph portrays a profile of defoliation pattern and tree heights by rows for a cross section of trees through the midsection of the plot. ... .. .. .. m...... OO© .0000 o 0.0.x 00H\\\\\ll. 000000000 0 0000 0 1000 0000 00009 000 m 00 000000000000000 OOO© 0 0000 00.00 0000.00 00 0000.00000000000000000000 00 00000000 00000 0000000000000 00000 000.0000 00.0 000 00 00000 000000. 0000000000 00 000001 m00000000000000000000 0000 m 00000000000000000000 00000000000000000000000000 0000000000000 0000000000 000 000000000000 00000000000000 C III FERN 1 5 onov ZO_._.<_1_Oumo 2): HIDE: wmmc. ROW Figure 3. 10 Red pine plot Al showing distribution pattern of trees defoliated by redheaded pine sawfly larvae in 1971. White = 0-9% defoliation; spot = 10-90% defoliation; black = 91-100% defoliation. Squares represent jack pine trees. Deliminated areas SC-II, SC-III are site class divisions. Fern refers to bracken fern occupying one SC-III area. Sand indicates a sand blow in the other SC-III area. The SC-II area had grasses and forbs. Lower graph portrays a profile of defoliation pattern and tree heights by rows for a cross section of trees through the midsection of the plot. DEFOLIATION (%) TREE HEIGHT (M) 11 sent scn scm @ ©©®O©O ® O..© 00 00000090000000 O©OOO©© OO©®©.O OOOO OO©OO®O©© .00 000000000. O 0 000000 ©©®OO©©©®©©©© 000 0 000 ® OOOO©OOOOOO @©@.© ©©. 00000000 00 © 0000 O©©©®.©@ ... OOOOOOOOOOOO OOOOOO OOOO.©O©...... 0000 00000000000 000000 .I. .III I 00 0 OOO OOOOOOOOOOO©®©...O...... OOOOOOOOOOO®OOO©OOO®®©. ©©. ...... OOO ©OOOOOOOOOOOOOO© ©.©O®.©®©©.. ©©®©OOOOOOOOO OO®OO®©.©...©©.... ©©@®.OOOOOO C9 O©OO ®©© . .@.. scm scn scm + SCIII ' SCII SCIJI I I 1 l FERN ' l l 5 10 IS 20 25 3O 34 Figure 4. 12 Red pine plot C1 showing distribution pattern of trees defoliated by redheaded pine sawfly larvae in 1971. White = 0.9% defoliation; spot = 10—90% defoliation; black = 91-10 % defoliation. Delimited areas SC-I and SC-II are site class divisions. 13 @300 OO©OOO©O scle OO©OO O 0 0 00000 0 00 0 0/9,,-/”' 0 0 000 0 0 000 0 00000 SCI 0 .O Ofl O OO O O 00 000000 000 OO 0 000 00 000000000 0 000000 000000 0000 0000000000 0 CO 00000 O 0 COO 00000000000 O 0000 OO O OOOO©O 00000 CO 0000 O O 0 000 00000 CO sun 0 CO 000 (MXXXDCKKmOOO COO. OOOOOOOOOCl C) (WW3 000 00000 CMXNWD O©OO @ CKKKXDCNDO COO C)C) CNSOOC> <30 Sui OCKXND OOC>CNDO. OOOOOO© OOO© 00000 000000 000 CO 00000 O O OO 0 000 O O OO CO 00000 OO O OO ©O©O 0000 0000 O 0000 CO OO O 0 000 O 00 OO ©OOOOOO 0000 000 O O 0000 O CO 00000 O 0 000 O O O O OO O 0000 00 O GO 0000 OO 00 O 0 000000 00 0000000 GOO GOO 000 0 00000 000 O O O O 0000 0000 000 CO OO©OO OO©OO 000 CO 00000 O 0000 O C©OCDOOJDCH3XD© :o AEmoazc LmZOFv MPEocz Emzo_ FFm Lo; vcm AEmnE:: Emaasv FLocz Emma: Low mEmpmzro mam mo mmmpcmoema .N mgsmwm QM IQm odltm 2): FIOEI mug. .v.NIm._ 0.. IN._ N._Iw.o 0.010 ¢w .5013 mw>>o.._ ZO o\o u mum—2:2 .5013 Emma: 20 .3. mum—232 29 Larvae in the DAR plots (C1, C2) consumed more foliage per insect than in other plots. The only apparent differences were site class and soil. DAR plots had Kalkaska integrating to Montcalm sand, while all the others had Kalkaska integrating to Rubicon. When regression equations were computed and covariance analyses made on their slopes the differences were significant at the .05 level (Figure 8). An average of 3.02 cm of foliated branch was consumed by each larva in the DAR plots and 2.53 cm for each larva in the other plots. The reason for these differences is unknown but a nutrient deficiency may have been responsible. In terms of colonies this means that the sawfly larvae in the DAR plots ate about one- fifthmore foliage than those in the other plots or 23.5 cm more. Though relatively a small difference this could be important when the trees are small, several sawfly colonies inhabit the same tree, or the sawflies are concentrated on the upper whorl. Defoliation within stands was also measured to determine the amount and location of damage. Estimates of defoliation were made each year fOr each tree in each plot and recorded after larval feeding as percentage of foliage missing (5% intervals) on the terminal shoot (leader) and the entire tree. Whole tree defoliation was distinctly related to site c1asses--the greatest defoliation was on SC-III trees and the least on SC-I trees (Figures 2 and 3, upper graph). In all plots where SC-III trees occurred, defoliation exceeded 90% per tree for about half of the trees (Figures 2 and 3, diagram), and nearly all of these had the leaders fully defoliated as well. Recall that SC-III 30 Figure 8. Red pine foliage consumed by sawfly larvae on trees growing on different soil series. FOLIATED BRANCH CONSUMED (cm) 500 as: a? . .——-487 450- d . O 400‘ ‘ KALKASKA— MONTCALM 0 " Y = -I5.58 + 3.49X I r2 = .889 350— KALKASKA - RUBICON Y = 27.55 + I.89X 300 r‘ = .8IO 250— 200- o . . . . a 'I O . ‘ . l50‘ . . . O o . O O 8 0° 7 . IOO— , , I / . . 006° . . .I . .. . 50" c - . ‘ . 1 . 1 8 0 fl I I r I I I I I I ' I I I ' I T 0 50 IOO I50 200 250 NUMBER OF LARVAE 32 sites also have the bulk of the insect p0pulation and contain the shortest trees on the average within each plot (Figures 2 and 3, lower graph). 0efbliation over 90% rarely occurred on SC-I and SC-II trees. Most trees on these sites were defoliated less than 10% which is insignificant to tree growth unless leaders are defoliated. Of the trees attacked on SC-I and SC-II sites only 3 and 10% of the leaders respectively were injured sufficiently to cause deformity or growth loss during the peak of the outbreak. I Factors Limiting the Sawfly Some of the limiting factors which affect sawfly p0pulations were examined, but a complete population dynamics study was not made because the study was begun at the peak of the outbreak, and shortly thereafter the population began to decline. However, some factors which seemed to modify the sawfly's behavior and survival were noted. Partial life tables were prepared based on the major biological com— ponents discovered in the plots. Egg and larval survival was studied in 1972 and 1973, in the Anderson and Boon Tower plantings. Egg clusters were selected on mean sample trees and followed through eclosion. Numbers of living larvae were tallied at the peak of each instar until the larvae left the host to pupate. Barriers were placed around several trees to contain the last instar wandering sawflies. These barriers were made of strips of 6" wide tin formed into a circle and sunk into the ground. The exposed portions covered with a sticky material kept most of the larvae from escaping. 33 Survival varied considerably between 1972 and 1973 (Table 6). Egg survival was 65% in 1972 and 36% in 1973. The egg parasite Closterocerus cinctipennis Ashm. was the most abundant agent and killed 85% of the eggs in some clusters and was the primary cause of mortality in both years. Larval survival varied also between the two years, but the causes were not investigated. Some of the larvae were parasitized but larval mortality from parasites rarely Occurs because the parasites do not kill the insects until they are in the cocoon stage. Nine species of parasites were reared from cocoons (Table 7). Benjamin (1955) noted 58 species of parasites and predators from N, lecontei. Perilampus hyalinus Say, which is a hyperparasite of diptera such as Spathimergenis spp., was the most common insect emerging from the cocoons. It contributed 16% mortality and the Spathimergenis erecta-aurifrons complex added an additional 3%. Benjamin (1955) also reported Perilampus as being common in 1948 and 1949 in Lower Michigan. Exenterus nigrifrons Roh., E, diprionis Roh., and E, amictorius Panzer were the next most common parasites. E, amictorius contributed 6% mortality. This European ichneumonid was introduced several times into Eastern Canada between 1933 and 1949 to control diprionid sawflies. The first record of it in Michigan was from Emmet Co. in July 1959. Besides being a parasite of N, lecontei, it also is established in N, swainei Midd. (McLeod 1972), N, sertifer Geoff. (Lyons 1964), and Diprion similis Htg. (Mertins and Coppel 1968). The higher rate of parasitization of E, amictorius compared to native Exenterus species suggests that it 34 TABLE 6.--Partial life tables for the redheaded pine sawfly in the Boon Tower Plantation in 1972 and 1973. Number Alive 0x as Survival Age Interval At Beginning Mortality Percentage (%) of Lx Dx of Lx Within x .1922. Egg 113 39 35 65 Instar I, II 74 7 9 91 Instar III 67 3 4 96 Instar IV 64 5 8 92 Instar V 59 - - - 1913 Egg 106 68 64 36 Instar I, II 38 l 3 97 Instar III 37 5 14 86 Instar IV 32 23 72 28 Instar V 9 - - - 35 no. mmFmEmm mum; Fm>w>gam mm. wmpme mum; Pm>w>gam I I I mmm mmamamwu c? mmwpdzmm mm 3 a 8 38353 8:23 22.8 mm 2 3 w? 3833 8:23 302 mm m cm Emcpo em 0 mm Aczocxczv mmmmmwo mm a Fm umcwsemumuczv mw>gm_ mpwmmgma w.mm N.o F mzpwpzuwom magpmmz m.mm N.o _ msumxmpunzm mzmmvcu ¢.mm 0.0 m mzconmmn mszaoFomFE «.mm 0.0 m wwmcmumcmo .m mm — o mmcovgawc .m cm m mm mswgopowEw magmpcmxm mm m my .agm mwcmmwmewspmam em o_ Pm mzcmfimxg msaEmpwEmm Nmm coouou x :Aanz x4 do xo x4 mo xo Low x , Axv mmmpcwuemm xwamquz mcwccwmmm p< m_nwmcoammm Logan; _m>cwp=H Fm>w>gam mm xo m>wp< cmnszz mm< comgmuc< cw mumpm cooooo mg» mcwgav >Fwam mama nmummgume 0:» .Nnm— cw cowpmucmpm Low w—nwp mmwp meugwaII.n m4m

w>L3m ”*chng mam xmmcnpaoIpmoa me am mmm mmm xemgnpzo mm mm omm mom xmmgnpzoImea HHH mm u _m>w>ezm pcmuema m_¢ xmmcnpzoIpmoa mm a mp wma xmmgnwso mm «P _n mmq xemenusoImEa HH mm n ~m>w>ezm CECULwa mmm xmwenpsoImeE mm N _ com xmwcnpso am m mm Nwm xmmgapzoImEa H x cwzpwz xp mo & Axov Axpv x Fm>Ewch mmmpu mama Fm>w>gsm & mm xo xpw_mpgoz pm m>wr< Co cowema mpwm .umcwneoo mpopa cowpmucmpa comgmuc< mcu c? meme» mcwa um; we mpnmu m$w4II.m m4m

_..._ xmmgnpzonEa pm mmmLF m>F4 poFa ”:F umFFFx mmmEF Fo Lamazz .cmmFgqu :F mpoFa acapm Fa xmmgnuso xFFzmm 05F mcFE:u zpFFmpEoE mcFa ummII.oF whmm0hmmm>o 00026de T O 4 d W 80-1 . . A . _ O O O 6 4 2 Fob >I_II_>>m 09.05:? mme. ROW 58 SC-II site. This was consistent with population levels in other plots--the SC-III sites had the most insects and generally the smallest trees. In this instance some very short trees (rows 1 and 2) along the south edge of the planting were free from insects (Figure 13). This is unusual but may have been due to the heavy shading from the hardwoods, or some microclimatic factor. Benjamin (1955), however, reported the sawfly preferred shaded trees for oviposition. Though red maple, Acer rubrum L. and other trees competed with red pine, young black cherry (Prunus serotina Ehrh.) trees scattered among the planting did not appear to do so. Root examina- tions showed that the maple roots occupied the same zone as the red pine while the cherry roots were below the red pine. Further, the cherry roots did not form dense mats as maple roots did. Red pine growth was also noticeably affected from competing ground cover (Table 11) especially in areas where bracken fern formed dense mats within plots such as in Al and A3 (Figures 2 and 3). In these pockets, rhizome and root mats filled the upper horizons of soil in the tree root zone. Tree height differences were usually dramatic at the interfaces where the fern patch ended and grasses, forbs, or lichens covered the ground. Plants other than bracken fern did not appear to have an effect on tree height. Apparently, both hardwoods and bracken fern are competitive to young red pines and growth loss in red pine is likely due to a reduction in available moisture. THE SITE Site, or the location in the environment which the tree and sawfly inhabit, is the modifying component of impact. It sets the constraints or boundaries of the development and interactions of and between the insect and the tree. Certain aspects of the site were examined to seek those parameters important for sawfly impact. The literature suggested that site quality and availability of water to the tree often affects populations of sawflies and other defoliators. For example, Gremal'skii (1961) summarizing the Russian work on the resistance of pine stands to defoliator pests, concluded that mass breeding occurs only in stands containing physiologically weakened trees. He noted causes of nutritional deficiency where survival rates with some insect pests was higher when fed foliage from weakened stands. White (1952) showed that N, lecontei larvae died after briefly feeding on jack pine seedlings grown on fertile nursery soil, whereas larvae on naturally reproduced seedlings taken from the forest and grown on unfertilized soil completely defoliated the host. Schwenke (1962), who studied the sawfly Diprion pini (L.) on trees growing on good and poor sites, found that survival rate and size of larvae was greater on trees from poor sites. He suggested that the unfavorable water balance in poor sites increased the sugar content of the needles which is probably the major limiting site factor for forest growth. He 59 60 further remarked that any suitable measure of site (direct or indirect) is, in effect, an estimate of soil moisture relationships. Soil Structure and pH The soils in the study plots and in other sawfly infested areas were examined to see if soil type or water holding capacity of the soil was related to the development of the tree and the size of the insect population. Two personnel of the Soil Conservation Service1 examined and classified the research plots to soil series. They classified plots Al, A2, A3, and BI as being composed of soil in the Kalkaska integrating to Rubicon phases. Plots Cl and C2 were soils of the Kalkaska integrating to Montcalm phases. Inter- preting from Hannah's (1967) soil classification system, the DAR Plantation (C plots) soils are more productive for red pine than those of the Anderson or Boon Tower plantings. The data agree with this. ' Local soil types were determined in plots Al and C1 by dig- ging soil pits in sawfly attacked and non-attacked areas. A 4-inch bucket soil auger was used to determine the solum characteristics between sawfly attacked and non-attacked sites in the other plots as well as the locations visited during the extensive survey con- ducted in Michigan, Wisconsin, New York, and Ontario, Canada. Varia- tion in soil texture, soil depth, and pH were examined for key differences. The pH was measured using a Hellige-Truog soil reaction test kit. 1SoiI scientists, 503, Cadillac, Michigan. 61 Gross site requirements for red pine are well documented. Wilde et a1 (1964) considers 10% silt plus clay to be the minimum fine particle ratio for adequate growth. On soils heavier than sandy loams, silt and clay have an adverse effect on red pine growth since they tend to restrict permeability and aeration (Van Eck and White- side 1963). In lower Michigan soils formed in deep sands, produc- tivity is also related to soil profile development. Hannah (1967) found a positive correlation between site index and the depth of the A and B horizons. At least 45-50 cm of reasonably permeable, fairly well aerated soil is necessary for normal red pine development. Below that depth, if the soil is compacted, very coarse, or calcareous, growth decreases after 25 years (Van Eck and Whiteside 1963). On the other hand, if the soil below 45 cm is medium-to-fine textured, the growth rate is likely to be rapid (White and Wood 1958). The influence of soil moisture, according to Stoeckler and Linstrom (1950), masks the influence of nutrients, possibly because higher nutrient levels are associated with finer textured soils. Excessive soil compaction can restrict root development (Armson and Williams 1960). Stone et a1. (1954) describe growth and survival of red pine in imperfectly and poorly drained soils. Best growth for red pine is associated with a soil pH of 4.5 to 6.0 (Wilde and Iyer 1962). A recent review of forest site quality evaluations by Carmean (1975) suggests an integrated approach to determining forest site quality. In some locations (Table 12, Appendix A) the sawfly was exploiting sites of low quality for red pine. Red pine growing in 62 TABLE 12.--Site parameters of redheaded pine sawfly infestations within plots examined in North America. P1329“? “2.13;? .5231. .2211... $53212 Appendix (pH) 1 dry coarse Sandblow 2 dry medium 3 moist medium Abandoned farmstead 4 dry medium Frost pocket 5 moist medium dense sod Frost pocket 6 dry coarse 7 dry medium Limestone and rock outcrops 8 wet fine 8.0 9 dry fine braken fern Limestone and rock outcrops 10 wet medium 7.0 11 dry medium 7.0 Frost pocket 12 moist fine dense sod 13 dry coarse 14 dry coarse Sandblow 15 dry coarse Overburden 16 dry coarse l7 moist medium Abandoned farmstead 18 wet ~ coarse l9 moist coarse hardwood edge 20 dry coarse 21 moist medium Compacted soil 22 moist fine 7.5 23 dry coarse Overburden 24 wet fine 25 dry medium A1 dry coarse 6.5 Sandblow A2 dry coarse 6.5 Sandblow A3 dry coarse 6.5 braken fern 81 dry coarse 6.5 hardwood edge Cl moist medium 6.2 Eroded C2 moist medium 6.2 Frost pocket 63 saldblows where the top soil was no longer present and the subsoil lacked a fine textured layer or color bands and red pine growing in poorly drained clay soils with a pH greater than 7.0, represented the extreme ends of the available moisture spectrum in which the trees were severely damaged by the sawfly. In the former situation, the lack of a suitable moisture holding capability and in the latter condition the excessive moisture holding capability represent sites where the establishment of red pine is not recommended (Bell 1971). The more pronounced the soil change between sawfly attacked and non-attacked sites within a plantation the more discrete was the damaged area. Other soil conditions which provided discrete pockets of sawfly activity were composed of soils severely compacted from old road grades and overburden soil (Table 12). In two instances the pocket effect of short trees and sawfly activity was adjacent to abandoned farm building foundations. These were rectangular pockets, suggesting that a prior cr0pping activity left the soil in poor condition. Within the study plots there was a definite gradation of soil characters between the three site classes that were set up (SC-I, SC-II, SC-III). For instance, in plot Al, the solum characteristics (Table 13) in the non-attacked portion of 50-1 suggests a more pro- ductive site by the presence of a leaching or A2 horizon and a some- what deeper soil with narrow texture and color bands than SC-III, which underwent severe sawfly attack. A more strongly developed upper B occurs in SC-I also. Portions of the SC-III upper B horizon were irregularly and strongly cemented in some locations. These 64 000m mmgmou 0.F ¢\F m>0.n +0F 0 scum mmcmou 0.0 w\0 m>0.F 0FIm0 mm FszoFEw> vmpcmsmo .ucmm mmemou 0.0 0\0 m>0.0 mcImm mm 000m mmcmou 0.0 N\N m>0F 0NINN EFm amooF .eeam emceau 0.0 F\m «FOF NNIO a< HHH =00I00 mwcmn CoFoo 0:0 Axopcp emv mucma ogspxmp 000m mmewo0 0.0 0\n 0>0.F +00 0 000m mmemou 0.0 0\0 0>0.m 00-00 mm vacmsmo zFxmmz .0cwm mmemou 0.0 0\0 m>0.n 00I00 N0 anmFEF .mucmm EstmE op 00F; 0.0 N\m m>0.m omem EFm 000m mmsmo0 0.0 N\0 m>0.F mmIom N< mmooF .0cmm mmgmou 0.0 F\¢ 0>0F 0NI0 F< H 000pme :0 CoFo0 F500 :pamo :oNFEo: mmmFu mppm .mmmgm Feexeappa »_acm>em0 HHHIom eea AcaxeappeIEOEV H-0m .F< papa cop moppmpcapeacaee asFom--.mF mgmap 65 -visib1e differences between 50-1 and SC-III within plot Al suggest that water and nutrients would be least available for red pine growth in the SC-III area. The growth response of the trees within the site classes reflect this difference in available moisture. In plot A3 the difference between SC-I and 50-111 was more subtle in soil characters (Table 14). Depth to the C horizon was 13 cm greater in SC-III. Both site classes show a less strongly developed soil profile than in plot Al. The principle difference occurred because there was a thick mat of bracken fern in A3 which competed with trees for moisture on a somwhat poorer site. In plot C1, the major soil difference between SC-I and SC-II sites was the light top soil erosion in the SC-II area. There was a more coarse textured and thinner Ap horizon in SC-II. Plot 81 was atypical in the degree of erosion and compaction. The road through the plot was previously a railroad grade. Just south of the plot the terrain sloped upward with a tree cover of maple. The soil on this slope has a very prominent A2 horizon. About 3 rows (6-7 m) into the planting the A2 horizon ceased and was replaced by an irregular bordered Ap-like horizon over the Bir. In the central portion of the plot, running north and south, is an area of compacted soil. South of the pine stand the compacted layer follows a course up the slope indicative of an old trail. Sawfly damage within the plot was more strongly aggregated within the com- pacted area south of the roadway. The compacted portion within the plot lacked an A2 horizon whereas south of the plot the trail had a narrow A2 horizon. Perhaps the sawfly was showing preference for an 66 0:00 000000 0.0 0\0 0>0.0 +00 0 0:00 000000 0.0 0\0 0>0.0 wmImm 0 0:00 000000 0.0 0\m 0>0.N wNINN 0Fm 0000F .0000 000000 0.0 m\m 0>0.0 NNI0 0< FHF 0:00 000000 0.0 0\n m>0.0 +00 0 0:00 000000 0.0 0\0 m>0.n 00I0m 0 0:00 000000 0.0 «\m m>0.m 0NI00 0Fm 0000F .0000 000000 0.0 N\0 0>0.0 0NI0 0< F 000px0F :0 00F00 F200 cp000 :00F00: 000F0 0me .00000 F00000pp0 >F000>00v HFFI00 00 F00000pp0Icocv HIum .m< p0F0 000 00Fp0F00p000000 EzFomII.0F 000< U] C) E $0 (I u] 2 _l E +3 RHTIFFIIITTIIIIWTIIIIHIIITFWI'ITI'II I935 1940 I945 I950 I955 1960 1965 1970 NORTHEAST LOWER MICHIGAN WIDESPREAD ENDEMIC PALMER'S INDEX +3 ‘1'II[IIIIIIIIIIITIIIIITTIlTlllllllll' I l935 1940 1945 I950 |955 1960 1965 1970 .F i... - 74 Figure 15. Sawfly populations and Palmer's Index values for the period 1935-1973 for the west and east regions of Michigan's Upper Peninsula. SAWFLY POPULATION SAWFLY POPULATION 75 WEST UPPER MICHIGAN WIDESPREAO LOCAL ENDEMIC x LIJ o .2. £0 a: LIJ 2 a' o. +3TTroITIIIllVTIITTIIITIPIIVTrT'lllTrITr 1935 |94O I945 I950 I955 1960 l965 I970 EAST UPPER MICHIGAN WIDESPREAD LOCAL ENOEMIC .4..1 g -3-1 z ’2‘ _|... 5.” a: OFF—FF..-" —— — FFFFFFFF —F_ '9' ET." +I- 0_ +29 +5 IlelTllTll‘T‘ITlrTIIITIIIIII'TWITIVII 1935 1940 I945 I950 I955 I960 1965 I970 78 appears that there is utility in the Palmer's Index for predicting outbreaks of this insect. 68 The data suggest that within plantations of red pine, those trees that are attacked heaviest by the sawfly (site class III areas) are characterized by one or more ofthe following: 1. Depth of parent material is significantly less (t-test P < .01) in attacked than non-attacked sites (mean 51 cm difference). 2. Soil pH in the upper 23 cm of the solum tends to be slightly acid to slightly alkaline on the attacked site (mean 7.0, range 6.5 to 8.0). The non-attacked sites tend to be more acid (mean 6.2, range 6.0 to 6.5). 3. Attacked sites may be composed of overburden soil and/or may be more compacted. 4. Soil texture is coarser on attacked sites and textural banding, when present, is less well developed. 5. On heavier soils attacked sites are imperfectly to poorly drained. Attacks in red pine plantations where there was no discern- able pocket activity,.as occurs in portions of Canada, were limited to those sites which had rocky outcroppings present and where the soil depth varied from 10 to over 75 cm to bedrock. Sawfly attacks on these sites were not as aggregated nor related to tree size or depth to bedrock (Table 12, Appendix A). Precipitation The historical records of sawfly activity and weather records were examined to determine whether sawfly outbreaks were 69 related to annual precipitation. The review of past outbreaks was done cautiously, since no standards exist and interest in the sawfly varied over time as did the number of or quality of reports. How- ever, by piecing together such subjective statements as "increasing," "decreasing," "static," and "widespread" as well as the number of reports filed each year, the relative density of the sawfly was determined over time. When populations became damaging, suppression efforts were conducted. Fowler (1973) provided a review of when and where chemical suppression was conducted against the sawfly on the national forests in the Northeastern Forest Service Region. Reports on file at the St. Paul Field Office2 and by Benjamin (1955) were reviewed for incidence of sawfly in Michigan from 1935 to 1971. Based on these reports, each year's population was classified as endemic, a local outbreak, or a widespread outbreak. The effect of various climatic factors either individually or in combinations is not fully understood. Thus, the Palmer method of drought index numbers was chosen to represent the intensity of drought and wet periods. These index numbers, given by Strommen et a1. (1969), are a function of accumulated weighted differences between actual precipitation and the precipitation requirement, where the requirement depends on: carryover of previous moisture, evapo- transpiration, moisture recharge and runoff that is appropriate for the area being investigated. Palmer's (1965) method is based on monthly departures of the weather from the average moisture of the month. Formulas have been 2U.S.D.A. Forest Service, St. Paul, Minnesota. 70 developed to provide index numbers and thus permit comparing particu- lar periods of interest with the average climatic conditions for the area. The index values are accumulative. Drought severity is usually discussed in four classes: mild, moderate, severe, and extreme by the Weather Bureau and the U.S. Department of Agriculture. Palmer (1965) arbitrarily assigned a drought index value of -4.0 to the accumulated monthly index values for the driest periods on record that he studied and called the class extreme. He divided the lesser accumulated monthly index values equally into drought index values of -l.0 mild, -2.0 moderate, and -3.0 severe. Conversely, values of +1.0 to +4.0 were assigned to describe wetter than normal periods. Michigan is divided into 10 climatic divisions to provide as much climatic homogeneity as possible to the users of the system. The redheaded pine sawfly has historically been a problem in the four northern divisions: West Upper, East Upper, Northwest Lower, and Northeast Lower. Red Pine growth is correlated with precipitation (Neary et a1. 1972). They showed a positive correlation between the amount of rainfall during July-September (the period of bud set), plus the following May and June (the period of water uptake) and annual bud length growth. To correlate both precipitation and sawfly with the host, Palmer Index values were used in the following manner. For each year analyzed, the average value for the months of April, May, and June, the period Of moisture uptake and sawfly oviposition, was added to the previous years average value for July, August, and 71 September, the period of larval activity as well as bud set. These values were then plotted over years along with the population density for each climatic division (Figures 14 and 15). It is evident in viewing these figures that the data fluc- tuates in both directions from the "normal" or 0 Palmer Index values and they generally are associated with population releases. Popula- tions usually collapse when the index values move back towarde. The least amount of climatic variation occurs in the Northeastern Lower Division, and this division historically has been affected by sawfly the least, only local outbreaks are recorded. The mean Palmer's Index values for each climatic division were plotted over broad categories of sawfly population density (Figure 16). Because of the larger variations associated with climatic data and the subjective evaluation of sawfly density, no absolute predictions can be made from the relationship. However, there is a strong relationship showing that endemic (very low) populations occur during moist periods, local (limited area) popula- tions generally occur during wet or near normal years, and widespread (large area) populations occur during drier periods. Analysis of variance of endemic and widespread values on Palmer's Index showed a highly significant difference (<.Ol, F1,100 = 8.5). The historical records did not provide information as to whether a given outbreak was on a wet or dry site. However, based on the extensive survey it appears reasonable to assume that outbreaks during the more moist years were associated with imperfectly to poorly drained soils. It Figure 14. 72 Sawfly populations and Palmer's Index values for the period 1935-1973 for the northeast and northwest regions of Michigan's Lower Peninsula. SAWFLY POPULATION SAWF LY POPULATION 73 NORTHWEST LOWER MICHIGAN WIDESPREAD LOCAL ENDEMIC )< u) C) E S.” a: LIJ 2 2% Q. +3 [I IT 1' I I I I l I I I I I Tfi I I l I I I I I I I I I I I I I I I I I I I935 I940 I945 I950 1955 1960 I965 1970 NORTHEAST LOWER MICHIGAN WIDESPREAD- LOCAL — ENDEMIC - .4.1 >< -3- 8 z ‘2‘ _'_. I” a: 04 u: 2 +I- ...l at. +2- +3 I I I I I I I I I I I I I I I I I I I I 1 I I I I I I I I I T I I I I I I I I I935 1940 I945 l950 I955 I960 I965 I970 74 Figure 15. SawfIy popuIations and Palmer's Index vaIues for the period 1935-1973 for the west and east regions of Michigan's Upper PeninsuIa. SAWF LY POPULATION SAWFLY POPULATION 75 WEST UPPER MICHIGAN WIDESPREAD LOCAL ENDEMIC >< UJ C) Z .9” (I n] E E +3jITfifiTfIII[IIIIIIIIIITfIIIVTIIIIIIIITTT— 1935 1940 I945 1950 1955 1960 I965 I970 EAST UPPER MICHIGAN WIDESPREAD LOCAL ENDEMIC -41 >< - - E: 3 z ’2‘ _'—I 5.0 a: oq-____._--_ _— _ ________ ___ E 2% +1- +3 IITIIITIIIIIIIIIIIITIIIIIIIIIIIIIIIIIT 1935 1940 I945 I950 I955 I960 I965 1970 Figure 16. 76 ReIationship of mean PaImer's Index vaIues to popuIations of sawfly in Michigan by regions. (The northeast Iower Michigan region did not have widespread population densities.) PALMER’S INDEX 77 -.9 WEST UPPER -.8- MICHIGAN -.T- -.6— -.5~ -.4_ MEAN 0F )ALI. REGIONS / "3‘ , ESSERV’EST / / /MICHIGAN -2- / EAST / UPPER / MICHIGAN — l— / / / 0— ———————— — ————— — / ———————————— ‘i / +.|— ) / I \ +.2"‘ / \ / NORTHEAST / LOWER +.3_ MICHIGAN +4— / / +05- / +.6— +.7~ +.8- +.9 I T ' ENDEMIC LOCAL WIDESPREAD SAWFLY POPULATION 78 appears that there is utiIity in the PaImer's Index for predicting outbreaks of this insect. DISCUSSION The Redheaded pine sawfly injures, and may kill, portions Of or all or a tree by removal Of both new and Old foliage. Trees that survive sawfly attack may exhibit crooks, multiple stems or branch deformity. The studies indicate that within a plantation the sawfly is strongly influenced by microsite conditions which the land manager can recognize. The land shows a capability to support various levels of sawfly population which inflict varying degrees of change to an established planting. Tree vigor appears to be the pivotal element on which the insect host—site ecosystem revolves. Stressed red pines are injured much more by the sawfly than are those growing well. The sawfly apparently prefers to attack shorter trees within a planting and tree height is one measure Of vigor as well as an indicator of the relative productivity Of the soil on which a tree is growing. Soil prodUCtivity is influenced by its nutrient content and its ability to hold moisture. When nutrients and/or available moisture becomes limiting to red pine, the trees become stressed. Three different site classes were identified which exhibited increasing susceptibility to sawfly which will henceforth be called site resistance classes (SRC—I, SRC-II, SRC—III) to distinguish them from standard site class terminology. Each site resistance class, because of its soil quality and moisture holding capability, is indicative 79 80 Of the potential to provide stressed growing conditions for red pine which are then subject to sawfly attack. The data Obtained in this study can be compiled in a model of sawfly impact. Ecological Model Of the Redheaded Pine Sawfly Sufficient information is available to construct a basic ecological model Of the sawfly. The model is based on the differ- ences between the three site resistance classes and major inter- relationships between the insect, tree, and the environment (Figure l7). Site resistance Class I (SRC—I) is highly resistant to the sawfly. It contains adequate soils for growing red pine. There the soils are relatively undisturbed or have a visible leaching (A2) zone. Also, these soils frequently have a B horizon which contains texture bands or well developed color bands. Bracken fern, if present at all, is sporadic; hardwood roots are rarely present in the same zone as red pine roots. In other words, there is, in general, little competition for available moisture from other sources. The amount Of water received by the trees is adequate and the soil has sufficient water holding capacity. Overall, SRC-I contributes sufficient nutrients and water for good red pine growth and the trees maintain high vigor as exhibited by their form, color, and annual growth. Even dry periods, which affect tree growth and vigor to some degree, do not weaken these trees enough to make them more attractive to the sawfly. Thus, these sites consistently pro- duce red pine that have a lower attraction for the sawfly. Further, 81 Figure l7. Ecological model of the redheaded pine sawfly. 82 ADEQUATE SOILS \SRC I SUFFICIENT 6000 WATER A r TREE HOLDING GROWTH CAPACITY I HIGH VIGOR POOR ATTRACTION T0 SAWFLY LOW EGG 8 LARVAL SURVIVAL LOW DAMAGE \ PRECIPITATION ADEQUATE sou-S \SRC ]I MARGINAL RELATIVELY WATER A GOOD HOLDING T TREE CAPACITY GROWTH PRECIPITATION POOR SOILS SOILS VARIABLE BRACHE NFERN COMPETITION SRC III POOR GROWTH I SOILS VARIABLE HARDWOOD COMPETITION POOR AVAILABLE MOISTURE \/ I PRECIPITATION MODERATE V IGOR GOOD ATTRACTION T0 SAWFLY HIGH EGG 8 LARVAL SURVIVAL MODERATE DAMAGE UNCHANGED STAND \/ LOW VIGOR EXCELLENT ATTRACTION T0 SAWFLY HIGH EGG 8 LARVAL SURVIVAL SEVERE DAMAGE v LIGHTLY CHANGED STAND (THINNING) \ INSECT — TREE DYNAMICS V HIGHLY CHANGED STAND (POCKETS) 83 the larvae exhibit some anabiosis, as survival is lower on SRC-I trees. Perhaps these trees are insufficient in some nutrient needed for Optimum larval growth. The little feeding that does occur causes only slight damage so that stand change is barely perceptible. There is seldom more than sporadic branch or leader mortality and whole tree mortality is rare. The stand, thus remains nearly unchanged and injured trees rapidly outgrow the effects of the sawfly (Figure l7). Site resistance class II (SRC-II) is more susceptible to the sawfly than SRC—I (Figure 17). The site contains adequate soils for nutrients but the upper solum is usually disturbed. The A2 horizon is only weakly developed and the B horizon lacks the degree Of development found in SRC-I soils. Bracken fern, when present, forms small clumps and hardwoods, at most, compete for only a small portion of the available moisture. On Kalkaska integrating to Rubicon phase soils the subtle difference between SRC-I and SRC-II is Often only exhibited in the degree of development Of the A2 horizon. At best, SRC-II soils have marginal water holding capacity and are sensitive to changes in precipitation. Extended drought can suffi- ciently weaken some of the trees making them more attractive to the sawfly. Normal and moist years, however, provide relatively good growth and moderate vigor. The SRC-II site is transitional between SRC-I and SRC-III but tree growth in most years is more like SRC-I trees. The sawfly is attracted to SRC-II trees more than to SRC-I trees, especially in dry years when the trees are stressed. Foliage appears adequate for high larval survival so damage from each colony 84 is maximized. The sawfly attacks the trees almost randomly or along margins Of SRC-III areas, where there is both a strong edge effect and more marginal soil properties. This attack site is not unusual as other sawflies exhibit the same phenomenon in pine plantations (Wilson l975). This means, however, that damage may be concentrated in certain portions of a stand. Resulting damage is usually moderate; scattered trees or ones along edges are injured. Defoliation occurs on apical portions of the trees and on entire trees. Tree mortality occurs but the degree varies by location and amount Of stress imposed upon the tree during the outbreak. The little damage from mortality modifies the stand slightly as a light scattered thinning of usually the weakest trees. Site resistance Class III (SRC-III) is highly susceptible to the sawfly (Figure l7). Some degree Of resistance occurs only in the most vigorous trees on this site, and these are usually on islands with better site conditions. In certain instances the soils may be poor in nutrients, pH, and water holding capacity due to previous practices. They may be severely eroded (sandblows), highly compacted, or composed Of coarse overburden soils. In other instances the soils are more variable and may even normally be adequate in nutrients and pH, but moisture availability is poor because Of competition from bracken fern on hardwood roots. Both form dense mats of roots in the red pine rooting zone so that any trend toward dryness greatly stresses the trees. Trees in this class are generally stressed in both normal and moist years and persis- tently respond by poor height growth, poor form, and Off-color 85 foliage. Their vigor is always low. The sawfly definitely prefers trees on this category and egg and larval survival is maximal, as there appears to be no anabiotic effect on them. Some attractant, such as a terpene violatilized in abundance when the tree is highly stressed, may be important to adult attraction. Terpenes are known tO attract pine insects (Wright and Wilson l972). Whatever the factor, the sawfly population appears to be released when poor available moisture is further reduced and drought occurs. Damage becomes severe in SRC-III areas. The attacked trees are small with many sawflies on each of them, so mortality is rapid and widespread. Most surviving trees become greatly stunted and severely deformed. The stand becomes highly modified by the end of an outbreak. Rows of trees are missing along hardwood edges and small to large pockets open up where poor soils or competing bracken fern occurs. Stands with larger or numerous areas of SRC-III may be almost completely depleted Of trees. Also, the larger and more numerous the SRC-III areas are in a planting the more SRC-II zones bordering them will be since SRC-II is transitional in nature. Some trees on the SRC-II area will also be damaged or destroyed. The implications Of the impact of sawfly damage for various degree Of site resistance areas in a stand are discussed in the socio-economic model section. Egpulation Dynamics Model Of the Sawfly Ecosystem There are many factors which interact to bring about a sawfly outbreak that results in severe host damage. Some Of these factors can be manipulated so that sawfly populations will be arrested before 86 intolerable damage occurs. Such factors can be examined through an insect-tree population dynamics model (Figure 18). Using host vigor again as the pivotal point Of the system the ecological and dynamics models can be interlinked (Figures l7, l8). Host vigor as noted before, determines the attraction of the female sawfly to the tree, and some degree of survival Of the egg and larval stages. Vigor in turn is regulated mostly by site con- ditions. Thus, any input that improves the site or one that improves the tree so that it is better able to utilize the site, will hamper the sawfly population. Certain treatments such as fertilization or irrigation Of poor sites can improve tree growth and increase vigor but such practices may currently be impractical. However, such treatments will be a part of forest management in intensive culture regimes in the future. Trees can be bred for more efficient site utilization, although red pine has particularly low genetic varia- bility. Even planting practices such as root depth might be modified to improve water availability to the roots. Competitive plants such as bracken fern might be thinned or destroyed prior to planting to provide more moisture to the trees. The sawfly, too, has many constraints or factors that limit its populations in most years (Figure l8). Some of these might be manipulated once a thorough population dynamics and key factor analysis has been made, and key factors, other than host vigor, are isolated. A few of the limiting factors were Observed in this study. For instance, a large portion of the egg population can be destroyed Figure l8. 87 Population dynamics model Of the redheaded pine sawfly--red pine ecosystem. (Host vigor [in circle] links this model to the ecological model.) W = winter, S = Seed, L1 to L5 = larval instars. 88 PREDATORS PARASITES LOW TEMP. PREDATORS PARASITES PREDATORS PARASITES DISEASES WEATHER MIGRATION INSECTS DISEASES ETC. I I PUPA 4 L SITE " FACTORS I II PREPUPA ADULT , I SAWFLY DYNAMICS I II _ PREPUPA A HOST ' EONYMPH EGG ‘ VIGOR II I I = 69*. La : L. : ' I I I I I I -------------- : : SAPLING SEEDLING I-«F—————J I I , __ ________________ __J I TREE DYNAMICS POLE MATURE 89 by an egg parasite, but more parasitization occurs on site resistance Class I. Perhaps parasite populations could be increased in SRC-III areas by habitat improvements. Increased parasitization has occurred following the cultural increase Of adult feeding hosts Of parasites Of the European pine shootmoth, (Rhyacionia buoliana (Schiff.)), (Syme 1966). Similarly, there are many parasites, predators, and diseases that influence the larval and pupal stages Of the sawfly. Rodents, which feed on sawflies in the cocoon stage, prefer certain habitats and are thus more effective in some localities. Low winter temperatures, perhaps during periods of sparse snow cover, could reduce the sawfly population. This, however, would be difficult to regulate. Also, the Northeastern Region Of the lower peninsula of Michigan has traditionally had low populations of the sawfly, even when outbreaks are occurring elsewhere. Site relationships do not appear to be better, yet something appears to be regulating the insect population. Perhaps some factor in the insect dynamics might be revealed in future studies to better understand this phenomenon, and use it to the detriment Of the insect. SociO-economic Model Public and some privately held forest lands are managed for a multiple of uses. Thus, multiple-use management implies managing for more than one purpose, though only one may dominate at a particu- lar location. While disagreement exists between parties practicing and criticizing this concept, it is Obvious and generally agreed upon, that management must consider the whole ecosystem in which 90 they are tasked (Figure l9). Management Objectives, in terms of quantified outputs, are what the sawfly is affecting. Without management objectives then, impact as defined herein, does not exist. Crosby (1977) points out that damage and value protection is goal oriented in his recent guide to the appraisal Of fire in the forest ecosystem. He translated broad USDA Forest Service goals into general Objectives to point out the diverse values that are at risk in fire protection. The same holds true for damage and value protection from the redheaded pine sawfly. Without translating management goals into quantified management objective outputs, it is impossible to calculate with a reasonable degree of precision the socioeconomic effects of an insect in the forest environment. Management Objectives affected by the sawfly are associated- both on the sites where the sawfly is physically present and Off these sites. Timber, wildlife, recreation and visual quality, forage for game and livestock, water and soil are all products of a forest ecosystem which may have management objectives that the saw- fly may effect (Figure l9). The degree Of the effect is tempered by the site resistance class on which the sawfly activity occurs. An impact risk rating guide based on expected physical change to tree form by SRC, was developed. TO risk rate a plantation to impact from this sawfly the percent occupied by each SRC is first determined using soil-site selections in Figure 20 as a guide. All combinations Of site resistance class are possible except SRC-I and SRC—III because SRC—II is transitional between these two classes. Risk is predicted from Figure 2l by comparing the dominent SRC 91 .AFCme Deva umumwszL mo Faces “Dogs? uwsocoum-owoom .m_ aLsmLL 92 CHANGE EXPECTED WITH SAWFLY AT TACK CHANGE EXPECTE D WITHOUT SAWFLY AT TACK I I V Y TIMBER YIELD RECREATION USE FORAGE AVAILABILITY WILDLIFE WATERSHED CHANGE CHANGE CHANGE CHANGE CHANGE SUM OF ON SITE PHYSICAL CHANGES SUM OF OFF SITE PHYSICAL CHANGES MANAGEMENT OBJECTIVE OUTPUTS AFFECTED PROJECTION TO TIME OF USE AND CALCULATION OF NET PRESENT WORTH WITH SAWFLY > WITHOUT SAWFLY NPW NPW POSITIVE IMPACT WITHOUT SAWFLY ) WITH SAWFLY NPW NPW V NEGATIVE IMPACT 93 Figure 20. Soil-moisture and tree growth relative to site resistance classes. 94 N.omra _ N.©Im.e Ia Qm2_4Homumm&2_ _ aomohao MZOAmm2_D _ _ 4.0m 3044o m30wm<04mo _ Azmza04m>mo D_Omm3m _ D_Omm3m _ szzaoUw>wo s_0mm:m ammo mDPP_D IP.3 moz2<04 m4_0m QmKDFXmH mmmH_4_m4Homummmz_ OH >4mooa m4_0m _ QmmDHXmH m4_0m ZD_Qw2 ommahxmk m2_u { _ Homm Hnomm _ Homm _ i: _ _ 28mg 30% 95 .mcowpwHCMFQ wcwa um; cw Dumas? >_w3mm mcwa umummgumg Low muwzm mcwgmL xmvm ._N aLsmLL 96 H 0mm >>aI_ ON Om