Proceediuqe of the 7th International Working Conference on Stored-product Protection. - Volume 2

Decrease in population size of Rhyzopertha dominica (Coleoptera: Bostrichidae ) at two temperatures in different wheat cultivars by the parasitoid (: ) *

Michael D. Toews", Gernt W. Cuperus, and Thomas W. Phillips

Abstract mcreased mterest m usmg entomophagous , such as A laboratory study was conducted to examine the role of the the parasitoid Theocolox elegans (Westwood) parasitoid Theccolax elegans in decreasing quantity of F1 (Hymenoptera: Pteromahdae ) , m managing pests such as Rhyzopertha dominica progeny. Expenments were Rhyzopertha dominica (F.) (Coleoptera: Bostrichidae ). conducted at two temperatures, 27.0 and 34.0°C, and in Rhyzopertha domuiica IS one of the most damaging and frve divergent cultivars of U. S wheat. Wheat stored in abundant pests of stored gram m the southern Umted States (Cuperus et al. 1986, Vela-Coiffier et al. 1997). ThIS glass Jars was infested with R. domuuca for four days and then the parental generation was removed wlule the progeny msect feeds m gram both as a larva and as an adult. were allowed to complete their life cycle Theocolax Detection of the species ISdifficult because larvae and adults tend to remain hidden inside the kernel (Fargo et al. 1989, elegans were released into half of the Jars and their progeny Vela-Coiffier et al. 1997). Females feed extensively and were allowed to develop. Adult progeny of pest and then lay eggs singly or in small clusters extenor to the parasitoid were collected and analyzed to access efficacy of kernels (Golebiowska 1969). The first instar then bores into the parasitoid at suppressing Its host. the kernel where It continues feeding on the endosperm, Increased suppression of the pest was detected at the molting 3 - 5 times before pupation The complete hfe cycle lower temperature when compared with the upper takes approximately 25 days at 34.0°C (BIrch and Snowball temperature. More parasitoids completed their life cycle at 1945, Howe 1950) Optimal developmental temperatures for the lower temperature, thus mcreasmg the potential for this species are 32.0 to 35. O°C (White 1995) but control m future generations. Analysis of interactions among development can be slowed by cooling the temperature of the the three trophic levels indicated that wheat cultivars did not gram (Howe 1950) significantly enhance the reproductive capacity of the Theocolax elegans IS a sohtary ectoparasrtoid that parasitoid. parasitizes beetle larvae within the kernel Sharifi (1972) provided an extensive list of possible hosts of T elegans. Potential SItes for oviposition are determined through mechanical detection using the antennae (Van Den Assem Introduction and Kuenen 1958) Dunng oviposition, the female inserts an egg into the kernel placmg it on the exterior body surface of the host larva. The larva of the parasrtoid continues to Biological control is an Important part of integrated pest develop extenor to the pest larva while both are still management (IPM) methods for stored grain. Parasitoids confined within the kernel. Theocolox elegans can complete and predators occur naturally m bulk stored grain facilrties one generation m approximately 25 days at 25. O°C (Van (Nilakhe and Parker 1990, Vela de Garza 1993, Gates 1995) Den Assem and Kuenen 1958). The developmental time for and are known to attack most msect pests of stored gram T. elegans is approximately one-half that of ItS hosts (Flmn (Hagstrum and Flinn 1992). In 1992 the U. S Food and et al. 1996). After emergence, the adult parasitoid bores Drug Admmistration (Anonymous 1992) exempted benefICial out of the kernel. msects from tolerance standards m stored gram. This has Few studies have been conducted utIhzmg augmentation of T elegarus to suppress R. dominica populations. Fhnn et

1Oklahoma State UruversIty, Department of Entomology and Plant al (1996) conducted expenments m steel gram bms m Pathology, 127 Noble Research Center, StIllwater, Oklahoma 74078 whIch thIS parasitOld speCIes was able to suppress R -3033 USA dominica populatIOns m excess of 90 % for two years * MDT WIll be presentIng trus paper compared to the unparaslhzed group In addItion, R 1231 Proceedrnqs of the 7th lnternatumal Worktng Conference on Stored-product Protection - Yolume 2 dominica populations were suppressed well below the existing infestations Gram was then cleaned by multiple Federal Grain Inspection Service (FGIS) standard of two passages over a seed cleaner (Clipper model M2B, Bluffton hve insects per kg for the' sample' grade designauon. Flmn Agncultural Industnal Corp , Bluffton, Indiana) and then (1998) also demonstrated that augmentative releases of T tempered to 13 ± 0.5 % moisture by either adding water or elegans were more efficacious when coupled with lower by ambient drying Whole wheat flour was added to each temperatures sample of wheat at a rate of one percent by weight to Ecologists use the term trophic or feedmg level to stimulate oviposition by R. donuruca . Wheat moisture delmeate an organism's place m the food cham (Lmdeman contents were determined using the ASAE standard dry 1942) The management system of concern m this paper weight method (Society of Agncultural Engineers 1996). includes the wheat cultrvar as the first trophic level, R Experiments were conducted WIth 75.0 ± 1.0 g of wheat dommica as the second, and finally T elegans as the tlurd in 0 2366 liter round glass cannmg jars. Forty, 2 - 3 week trophic level. Interactions among these three trophic levels old unsexed R dominica adults, from OSU stock cultures are collectively termed 'tntrophlc mteractIons' An reared on the hard red winter cultrvar '2163' , were added Important consideration among tntrophic mteractions IS that to each jar for a four-day oviposrtional penod All Jars were members of the first and third trophic levels may act m a kept at 30.0 ± O. 5°C in an environmental chamber mutuahstic manner (Pnce 1986) Starks et al. (1972) (Percrval-Scienufic Corp., Model 1-35 LVL) durmg the studied relationships in a cereal field crop ecosystem and mitial oviposrtional penod m order to begin With an quantified Important observations pertinent to other approximately equal number of eggs in each jar. Followmg ecosystems Of primary concern m their study and several the ovipositional penod, gram was gently sieved over a 1.40 others was the concept that the pnmary trophic level, I E. mm standard dockage SIeve. Beetles were collected below the host plant of the herbivore, could influence development that SIeveon a 0.21082 mm SIevewhile the dust fell through and survivorship of a carnivorous species at the third tropluc both SIeves to be collected m a bottom pan. Wheat and dust level (Starks et al. 1972, Reed et al 1991, 1992, 1993, were returned to the jars for the duration of the expenment. Reitz and Trumble 1996). A second Important aspect of Ventilation was permitted through filter paper held m place these studies was that activIty of parasitOids at the thIrd by the cannmg nng. Samples were mamtamed at eIther trophIC level can mfluence the extent of feedmg damage to 27.0 ± 0 .5°C or 34.0 ± 0 .YC and 70 ± 5% rho Completely the plant speCIes Fmally, biOlogIcalcontrol and host plant dark condItions were utilIzed throughout the expenment resIstance can be hIghly compatible m the development of Hygrothermographs were mamtamed mSIde each successful pest management programs (Salto et al. 1982). envIronmental chamber to momtor any changes m Objectives of thISstudy were to (1) evaluate the effects of temperature or humIdIty wheat cultIvar, temperature, and the parasitOid T elegans, Expenments were conducted m a splIt plot arrangement m on the number of adult R dommica progeny, (2) WhICh the mam plot was temperature, arranged m a determme percent suppreSSIon of adult R. donnmca completely randomIzed deSIgn, whIle the subplot treatments progeny due to T elegans, (3) compare the abIlIty of T. were cultIvar and presence of the parasitOId, arranged m a elegans to complete ItS lIfe cycle under the mfluence of the randomIzed complete block. Subplot treatments were dIfferent temperatures. blocked across the envIronmental chambers from left to nght because an earlier umformlty tnal mdlcated dIfferences m a Materials and Methods chamber Each envIronmental chamber represented one applIcation of 'temperature' while subplot treatments were FIve cultIvars of wheat (Tntwum aestz1mm 1.) were each replIcated four times wlthm each chamber. The procured from commercial seed producers and vanous expenmental umt at the subplot level m thISexpenment was foundation seed stocks across the Umted States. Wheat a jar of wheat mfested WIthR donumca. Wlthm a subplot cultIvars represented dIvergent genetIc lmeage and replIcatiOneach wheat cultivar was represented two times, resistance to common field pathogens and msects. Selections once m the absence of the parasltoid and once WIth the mcluded the hard red wmter cultivar '2163' (Oklahoma parasitOid present. Each expenment mcluded two Foundation Seed Stocks, Inc , Stillwater), soft red wheats replIcations of temperature (two chambers at each 'Coker 916' (NovartIs Seeds, Inc., Bay, Arkansas) and expenmental temperature), eIght replIcations of each 'WakefIeld' (Arkansas Agncultural Expenment Station, cuItIvar WIth parasltOids per temperature, and eIght FayettevIlle), the durum wheat 'Mumch' (North Dakota replIcations of each cultIvar WIthout parasitOids. Seedstocks Project, Fargo) and a whIte spnng wheat, TIme of beetle and parasitOid mtroductIon and removal , WawawaI' (Washington State Crop Improvement times are summanzed m Table 1. All adult T elegans were AsSOCiation,Pullman) Followmg receIpt wheat samples less than three days old when released mto the gram. were frozen for one week to elImmate the poSSIbIlItyof ParasitOidswere reared m stock colomes on R donunica m 1232 Proceedwgs of the 7th lnternational Workzng Conference on Stored-product Proteciuni - Yoiume 2

'2163' wheat FIve male and 10 female parasitoids were expenmental temperatures were estimated With a degree released at each release time. Previous research (Toews, day model developed by Subramanyam et al. (1990). The unpublished) indicated that generation time for R model used a threshold temperature of 13.2°C for egg to dommica vaned among wheat cultivars Due to the adult development of R dominica., All msect mtroduction possibility of a smgle parasitoid release bemg optimally and removal times were calculated to occur at the same timed for a given cultrvar contammg the appropnate host degree day mtervals m both temperature treatments. Data stage, two parasrtoid releases were utilized. ThIS method analysis was performed only on the total number of progeny msured that live parasitoids were present when their hosts collected and not broken down by mdrvidual collection reached the optimum age for parasitism DIfferences in R mterval domuuca developmental times at the two different

Table 1. Introduction and removal times for R domiruca and T elegans T. eleqou« T. eleqans T elegans R. domuuca and R domtnica and Temperature Released Released Removed T. elegans removed T elegans removed DIY DD Day DD Day DD Day DD Day 343.2 24 453.6 32 564.0 40 771.0 55 978.0 70 337.6 17 441.6 22 566.4 28 774.4 38 982.4 48 a Degree Days based on a model by Subramanyam et al (1990) b Actual Calendar day of expenment startmg WIthadult R domnuca release when all Jars were held at 300°C for four days accountmg for the first 67 2 degree days m this table; after the four-day ovipositional penod the adult R domuuca were removed and Jars moved to their respective temperatures If 24 actual calendar days are shown m this table then the first four days were at 300°C and the other 20 days are at the expenmental temperature

Data were analyzed using SAS (SAS Institute Inc 1994). Before statistical analysis progeny counts were transformed Results using a square root transformation while percentages were transformed usmg the arcsme transformation (Zar 1984) to Temperature was not a contnbutmg factor to vanabihty in correct for heteroscedastic data Treatment means were the number of R. domiruca adult progeny recovered m compared at the a = 0.05 level usmg the LSD method (PROC gram WIthout T elegans (F = 0.24; df = 1,2; p = GLM, MEANS LSD LINES) (Steel and Torne 1980) o .6733) At 27. O°C, a mean of 358.7 ± 29.6 beetles Parasitoid counts were analyzed usmg PROC GLM; emerged, while at 340°C, 398.1 ± 26.6 beetles emerged however, tlus method does not account for vanabilrty at the per Jar of wheat Numbers of R. dorniruca progeny in first trophic level from a cultrvar that harbors only a few gram WIthout T elegans sigmficantly vaned due to wheat beetles and consequently only a few parasitoids, To relate cultrvars (F =6.52; df = 4,56; p = 0.0002) (FIg. 1) the number of parasitoids emerged to cultrvar effects, a Total numbers of adult progeny by cultrvar ranged from "parasitotd progeny mdex ' was created. ThIS mdex was 248.9 ± 27.5 beetles to 487.4 ± 51 .4 beetles per Jar. The determmed by drviding the total number of parasitoids cultrvars 'Wawawai ' and 'Mumch' harbored fewer numbers emerged from each treatment Jar by the total number of of R domuuca than the remammg cultrvars beetles emerged from the control Jar of the same cultivar in The higher temperature had a significant mfluence on the the same replication ThIS mdex was needed to fully suppression of adult R dominuxi by T elegans when quantify the tntrophic nature of the study When usmg the compared with the lower temperature (F = 17.78; df = 1,2; parasrtoid production index, numbers of T eleqans are P = 0.0519) At 27°C the number of R dommca suppressed related to the number of emerged beetles ill the wheat were 81.5 ± 3 1% whereas 51.3 ± 5.7% were suppressed WIthout parasrtoids and therefore the effect of cultivar on at a higher temperature. The were no differences in percent beetle numbers ISadjusted appropnately ParasltOld progeny suppression of R danwuca progeny attnbutable to the mdex data were analyzed usmg PROC GLM (SAS InstItute dIfferent cultlvars (F = 1.72; elf = 4, 55; p = 0.1580) Inc. 1994) and were not transformed Values for percent ( FIg. 2) SuppreSSiOnof R elanL~lIwa ranged from a suppreSSiOnof R donwZlca caused by T. elegans were mmlmum of 56.9 ± 8.2 % m 'Wawawal' to a maXImumof obtamed by dlvldmg the number of R domlnlca adults 73.3±8.5% m '2163' from the Jar WIth the parasltOlds present by the number of Temperature had an Important effect on the recovery of adults from Jars WIthout the parasltOlds m the same adult parasltOld progeny (F = 9.94; elf =1,2;p = replication. The resultmg number from that calculation was 0.0876) WhIle a mean of only 24.2 ± 5.3 T. elegans then subtracted from one and multiplied by 100 emerged from wheat samples held at 34. O°C, a mean of 1233 Proceedings of the 7th International Working Conference on Stored,.p"·od'uctP1'Otection- Volume 2

200,- ""] 206.5 ± 16.0 parasitoids emerged from grain held at 27.0'C . Fewer T. elegans progeny emerged from 180

'Wawawai ' than from the remaining cultivars (Fig. 3). 160

This was expected since this cultivar also harbored the 140 fewest number of R. dominica. >. 120 e The parasitoid progeny index was significantly higher at & 100 27.0L: than at 34.0'C (F = 19.93; df = 1, 2; p = ~ 80 0.0467). At the higher temperature the mean parasitoid progeny index was only O. 11 ± 0.03 while at 27. O°Cit was 60 0.69 ± 0.09, This index was not influenced significantly by '0 wheat cultivar (F = 1.80; elf = 4, 56; p = 0.1416) 20 ( Fig. 4). Values for the index averaged over both o 'Waker~d' temperatures ranged from a minimum of 0.27 ± 0.07 Cultlvar parasitoids per available host in 'Wawawai ' to a maximum of n = 16;F = 10.52; dj = 4,56; p = 0.0001. Means followed 0.58±0.20 parasitoids per available host in 'Munich'. by the same letter are not significantly different (p >0.05;

0.8 ,---- ~-----,

0.7

0.6

zoo ~ 0.5 E ~ 0.4 100 ~

~ 0.3 o .. Wabfteld' '2183' "Coker.1" 'Munidl' 'Wawewai' 0.2 Cultivar n = 16; F = 6.52; dj= 4, 56; p = 0.0002. Means followed 0.1 (p by the same letter are not significantly different >0.05; 0.0 Fishers LSD Test). 'Wakefield' '2163' 'Coker 916' 'Munich' "Wawawai' Cultivar dominica Fig. 1. Mean± SE R. adult progeny from wheat n = 16;F= 1.80;df=4,56; p = 0 .1416. without T. elegans present. Fig. 4. Mean± SE T. elegans progeny production index. 100 I~~ __ ~~ ~~ __ ~~_ Discussion 80

The functional response concept is a useful tool to help explain differences in beetle suppression between these temperatures. The functional response is defined as the change in the number of hosts consumed or parasitized (stung) by individual predators or parasitoids as the density

20 of the prey/host changes (Solomon 1949, Holling 1959). Later, Mack and Smilowitz (1982) suggested that search o rate, a component of the functional response, decreased in 'Coker 916' 'Munich' 'Wawawai' relation to increasing temperatures above 30.0°C for the Cultivar predator Ccleomeqilu: maculata (DeGeer). (Coleoptera: n = 16;F= 1. 72;df=4,55;P=0.1580. Coccinellidae). In this experiment, the functional response Fig. 2. Mean percent ± SE suppression of recovered R. describes the number of R. dominica stung by T. dominica adult progeny when parasitized by T, elegans. An increase in the search and handling time due to elegans, the higher temperature, could have caused the lower rate of 1234 Proceedmqs of the 7th Internatwnal Working Conference on Stored-product Protection - Volume 2 suppression of the host, smce there were not enough (gram). HIgh temperature sigmficantly decreased T. parasitoids to stmg the number of available hosts. At the elegans progeny recovery. Efficacy of the parasitoid and the lower temperature, the parasitoids were able to attack their number of parasitoid progeny were both mcreased at the hosts more quickly and hkely parasinzed a higher proportion lower temperature, potentially mcreasmg the opportunity of the pest population These data Imply that temperature IS for successful control. The first trophic level, wheat an important component of the functional response for T. cultrvar , did not SIgnificantly affect the parasitoid production elegans. mdex but did affect the recovery of R. dominica progeny In this expenment , the 34. O°C temperature sigmficantly in wheat Without T. elegans. There were no differences decreased the recovery of adult parasitoid progeny. attnbutable to temperature m the number of R. dominica Possibly, the high temperature prohibited a certam progeny recovered in grain WIthout T. elegans. physiological event from occurnng in the hfe cycle of the parasrtoid, Another hypothesis IS that hosts at the high References temperature are bemg stung, thus paralyzmg the beetle larvae, but adult female parasrtoids are not depositmg eggs; Anonymous. 1992 Parasrtic and predaceous insects used to tlus behavior has been shown with another species of stored control pests: Exemption from a tolerance. Federal grain parasi toid (Flmn 1991) Register 57, 14644 - 6. Solomon (1949) described the numerical response, BIrch, L C. and Snowball J. G 1945. The development of defined as a change m the number of predators, as a function the eggs of Rhyzopertha donunica Fab. (Coleoptera) of prey density from generation to generation Aust. J. Exp BIOI. Med. Sci. 23, 37 - 40. Entomophagous msects in biological control studies usually Cuperus, G. W. , Pnckett C. K. , Bloome P. D. , and Pitts control pest populations through changes m the numencal J. T. 1986. Insect populations in aerated and unaerated response (Huffaker et al. 1968). The current expenment stored wheat m Oklahoma. Journal of the Kansas does not mclude conclusions on the numencal response of Entomological Society 59, 620 - 627. the parasitoid because these conclusions would require data Fargo, W. S. ,D Epperly, G. W. Cuperus, B. C. Clary, from several generations. However, m both of these and R Noyes 1989. Effect of temperature and duration of experiments, sigmficantly more T. elegans emerged per trapping on four stored gram msect species. Journal of available host at the lower temperature than at the higher Economic Entomology 82, 970 - 973 temperature Assummg that host density IS not a lmutmg Flinn, P. W. 1991. Temperature-dependent functional factor and that more parasitoids are able to parasitize an response of the parasitoid Cephalanomia waterstani mcreased number of hosts, the potential for a numencal (Gahan) (Hymenoptera: Bethyhdae) attacking rusty gram response should mcrease at 27. O°C, compared to 34. O°C. beetle larvae (Coleoptera: Cucujidae ) . Environmental Addrtional research targetmg the numencal response for this Entomology 20, 872 - 876. parasitoid IS needed to address these possibilities. Flmn, P. W. 1998. Temperature effects on efficacy of Cultivar played a hmited role m the association among Choetosptla elegans (Hymenoptera: Pteromalidae ) to trophic levels. DIfferences m T. eleqams progeny recovered suppress Rhyzopertha dominica (Coleoptera: among cultrvars were hnked to the mcreased number of R Bostnchidae ) m stored wheat. Journal of Economic dominica hosts m those same cultivars. The parasrtoid Entomology 91, 320 - 323. progeny production index provides more information on the Flmn, P. W., Hagstrum D. W., and McGaughey W. H. influence of the wheat cultrvar on the parasitoid A higher 1996. Suppression of beetles in stored wheat by parasitoid production mdex value, such as that calculated for augmentative releases of parasitic wasps. Environmental 'Munich' suggested that the first trOphIC level IS poSItively Entomology 25, 505 - 511. mfluencmg the third trophic level. More parasitOlds Gates, M. W. 1995. Population dynamics of lesser grain emerged per potential host on the cultIvar 'Munich' than in borer, rusty gram beetle, and Cephalanornia waterstani , Wawawal " however cultIvar was not a statistically in commerCial elevators. M S. thesis, Okla. State U. , SIgnificant factor contributmg to differences in the mdex Stillwater. value m either expenment. Golebiowska, Z. 1969. The feeding and fecundity of Sitophil1J.Bgranari1J.B (L.), Sitophil1J.Boryzae (L.), Conclusions and Rhyzopertha domintca (F ) m wheat grain. Journal of Stored Products Research 5, 143 - 155 T. elegans played an important role m suppressing progeny Hagstrum, D. W. and Flinn P. W.. 1992. Integrated pest of R. domin'tCa. SuppresslOn of the second trophic level management of stored-grain insects, pp 535 - 562 In D. (R. domintca) by the third trophic level (T. elegans) B. Sauer [ed. ] ,Storage od cereal grains and theIr product. will prevent exceSSIve losses at the fIrst trOphIC level American AssoCIation of Cereal ChemIsts, S1. Paul, MN. 1235 Proceedmgs of the 7th International Worknl{} Conference on Stored-product Protection - Volume 2

Hollmg, C S 1959. The components of predauon as Salto, C E., Eikenbary R D and Starks K. F. 1982 revealed by a study of small-mammal predation of the Compatibility of Lusiphlebus teetacerpes (Hymenoptera: European Pme Sawfly Canadian Entomologist. 91, 293 - Brocorudae ) WIth green bug (Homoptera: Aphididae ) 320. biotypes 'C' and' E' reared on susceptible and resistant Howe, R. W 1950. The development of Rluzopertha oat vaneties Environmental Entomology 12: 603 - 604 domuuca (Col. , Bostncludae) under constant conditions SAS Institute 1994 SAS/STAT guide for personal The Entomologist's Monthly Magazine 86. 1 - 5 computers, version 6 10 ed. SAS Institute Cary, North Huffaker. C B., Kennett C. E.,. Matsumoto B, and Carolma. White E G 1968. Some parameters m the role of Shanfi, S. 1972 Radiographic studies of the parasite enemies m the natural control of msect abundance pp 59 Choetoepda elegans on the maize weevil, Sitoplut us -75 In Symposia of the royal entomological SOCIety of zeanuuze Annals of the Entomological Society of London: number four, Insect Abundance Ed TRE. Amenca, 65: 852 - 856 Southwood Blackwell SCl. Pub Oxford. Society of Agncultual Engineers 1996 ASAE standards: Lindeman, R L 1942. The trophic-dynarmc aspect of standards, engmeenng practices and data adopted by the ecology Ecology 23, 399 - 418 Amencan Society of Agncul tural Engmeers Procedure Mack, T P and Smilowrtz Z 1982 Usmg temperature- S352 .1. 31st ed The Society of Agncultural Engmeers. mediated functional response models to predict the Impact St Joseph, MI of Coleomenlla maculata (DeGeer) adults and 3rd-mstar Solomon, M E 1949 The natural control of ammal larvae on green peach apluds Environmental Entomology populations The Journal of Ecology, 18: 1- 35. 11, 46 - 52 Starks, K., Mumappan, Rand Eikenbary R 1972. Nilakhe , S. S. and Parker R D 1990 Implementation of Interaction between plant resistance and parasrtism agamst parasites and predators for control of stored-products the green bug on barley and sorghum Ann Entomol Soc pests, pp. 241- 250. In Proceedmgs, 3rd National Stored Amer. 65: 650 - 655 Gram Pest Management Trammg Conference, October 20 Steel, R G D and Torne J H 1980 Principles and - 25, 1990, Kansas City, MO. procedures of statistics 2nd ed. Mcflraw-Hrll , Inc. New Pnce, P W. 1986 Ecological aspects of host plant York. resistance and biological control: mteractions among three Subramanyam, B H , Hagstrum D Wand Harem P K . tropluc levels, pp 11 - 30 In D J. Boethel and R D 1990. Upper and lower temperature thresholds for Eikenbary [eds J, Interactions of plant resistance and development of SIX stored-product beetles, pp 2029 - parasitoids and predators of insects Ellis Horwood 2037 In Proceedings of the fifth mternational workmg Lmu ted, Chichester, U K conference on stored - product protection Boreaux, Reed, D K, Burd, J. D. and Elhott N C 1993. France. Sept 9 - 14, 1990. Aspects of tntropluc interactions of RUSSIan wheat aphid, Van den Assem, J and D J Kuenen 1958. Host fmdmg 109 - 113. In ACS conference proceeding senes , pest of Choetoepila elegans Westwood (Hym Chalcld) a management: biologically based technologies. ed R D parasite of Snophilu« qranarius L (Coleopt. Curcul ). Lumsden and J L Vaughn Amencan ChemIcal SoCIety Entomologla Expenmentahs et Apphcata 1, 174 -180. Reed D , Kmdler S , and Spnnger T 1992. Interactions Vela de Garza, E L 1993 RelatiOnships among fhght of RUSSIan wheat aphId, a hymeropterous parasitOld and trap, pItfall probe trap, gram tner and deep cup probe reSistant and susceptible slender wheatgrasses methods m samplmg stored wheat msects M S theSIS, Entomologia Expenmentahs et Apphcata 64, ,239 - 246. Oklahoma State Umverslty, Stillwater Reed, D , Webster J ,. Jones B, and Burd. J 1991 Vela-COlffler, E L, W S Fargo, E 1. BonJour, G Tn trophiC relationshIps of RUSSIan wheat aphid W , Cuperus, and W D Warde 1997. ImmIgration of ( Homoptera: Aphldldae), a hymenopterous parasitOld Insects mto on-farm stored wheat and relatiOnshIps among (IJuwretlella rapae McIntosh), and reSistant and trappmg methods Journal of Stored Products Research 33, susceptible small grams. BiOlogIcal Control 1,35 - 41 157 -166. ReItz, S R., and Trumble J T. 1986 Tntrophlc WhIte, N D., 1995 Stored Gram Ecosystems. ed D. S mteractiOns among lmear furanocoumanns, the herbIvore Jayas, N D G WhIte, and W. E. Mmr Marcel Dekker, Tnchopl usia n'/, (Lepldotera: Noctmdae), and the Inc New York polyembryomc parasitOld Copzdosoma floridanum Zar, J H 1984 BlOStatlstlcal analYSIS. 2nd ed. Prentlce- (Hymenoptera: Encyrtldae). EnVironmental Entomology Hall, Inc Englewood Chffs, New Jersey 25,1391 - 1397.

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