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BIOLOGICAL AND MICROBIAL CONTROL Potential of Trichogramma ostriniae (: ) for Biological Control of (: Crambidae) in Solanaceous Crops

THOMAS P. KUHAR,1 VONNY M. BARLOW, MICHAEL P. HOFFMANN,2 SHELBY J. FLEISCHER,3 ELEANOR GRODEN,4 JEFFREY GARDNER,2 RUTH HAZZARD,5 MARK G. WRIGHT,6 2 5 SYLVIE A. PITCHER, JOHN SPEESE III, AND PAM WESTGATE

Department of Entomology, Polytechnic Institute and State University, Eastern Shore Agricultural Research and Extension Center, Painter, VA 23420

J. Econ. Entomol. 97(4): 1209Ð1216 (2004) ABSTRACT We assessed the ability of Trichogramma ostriniae (Peng & Chen) to locate and parasitize Ostrinia nubilalis (Hu¨ bner) eggsin cropsother than corn, and we evaluated the efÞcacy of inundative releases of the in two solanaceous crops, pepper and potato. Despite a greater surface area to search, parasitism of O. nubilalis eggs was consistently higher in than dicotyledonouscropssuchaspepper, snapbean, broccoli, potato, and melon, in choice and no-choice experiments. Nonetheless, in 2002 and 2003, we made four to Þve separate inundative releases of Ϸ30,000Ð50,000 T. ostriniae per 0.02 ha in nine pepper Þelds in Virginia, , and Massa- chusetts and compared O. nubilalis egg parasitization and fruit damage in those plots with spatially isolated nonrelease plots. Egg parasitization averaged 48.7% in T. ostriniae release plots, which was signiÞcantly higher than in nonrelease plots (1.9%). Also, cumulative pepper fruit damage averaged 8.7% in release plots, which was signiÞcantly less than in nonrelease plots (27.3%). In potatoes in 2002 and 2003, we made two releases of Ϸ75,000 T. ostriniae per 0.2 ha in nine Þeldsin and Virginia and compared O. nubilalis damage in those plots with that in nonrelease plots. T. ostriniae releases signiÞcantly reduced the number of tunnel holes and number of O. nubilalis larvae in potato stems. We conclude that thisparasitoidhasgreat potential asa biocontrol agent for O. nubilalis in solanaceous crops.

KEY WORDS Ostrinia nubilalis, parasitoid, pepper, potato, biocontrol

Trichogramma ostriniae (Peng & Chen) (Hymenop- successfully parasitize O. nubilalis eggsthrough most tera: Trichogrammatidae) hasreceived particular at- stages of embryonic development (Hoffmann et al. tention in recent yearsasa biological control agent of 1995) and sustain a relatively high Þtness level after European corn borer, Ostrinia nubilalis (Hu¨ bner), in many generationsof development on factitioushosts corn (Wang et al. 1999; Wright et al. 2001, 2002; Hoff- such as Ephestia kuehniella (Zeller) (Lepidoptera: mann et al. 2002; Kuhar et al. 2002, 2003a). The para- Pyralidae) or Sitotroga cerealella (Olivier) (Lepidop- sitoidisendemic to China where it isan effective tera: Gelechiidae) eggs(Hoffmann et al. 2001). In natural enemy of the Asian corn borer, Ostrinia fur- addition, T. ostriniae iscold hardy and can survive nicalis Guene´e (Hassan and Guo 1991, Smith 1996). prolonged storage (Smith 1996, Pitcher et al. 2002). Laboratory research has shown that T. ostriniae can Field research with T. ostriniae in the has focused on releases in sweet corn in the northeast. Wang et al. (1997) and Wright et al. (2001) demon- Any opinions, Þndings, conclusions, or recommendations expressed strated proÞcient dispersal and host Þnding. In Mas- in this publication are those of the author(s) and do not necessarily Ͼ reßect the view of the United StatesDepartment of Agriculture. sachusetts, Wang et al. (1999) achieved 40% para- 1 E-mail: [email protected]. sitism of O. nubilalis eggswith four releasesof Ϸ34,000 2 Department of Entomology, Cornell University, Ithaca, NY 14853. T. ostriniae per hectare. More recently in , 3 Department of Entomology, Pennsylvania State University, Uni- versity Park, PA 16802. Hoffmann et al. (2002), Kuhar et al. (2002), and 4 Department of Biological Sciences, University of Maine, Orono, Wright et al. (2002) demonstrated that a single inoc- ME 04469Ð5722. ulative release of T. ostriniae (Ϸ70,000 per hectare) 5 Department of Entomology, University of , Am- could provide season-long parasitism of O. nubilalis herst, MA 01003. 6 Current address: Department of Plant and Environmental Pro- eggsand reduce ear damage by 50%. Also,Hoffmann tection Sciences, 3050 Maile Way, University of Hawaii at Manoa, et al. (2002) demonstrated that T. ostriniae persisted in Honolulu, HI 96822. commercial Þelds after insecticide applications, that

0022-0493/04/1209Ð1216$04.00/0 ᭧ 2004 Entomological Society of America 1210 JOURNAL OF ECONOMIC ENTOMOLOGY Vol. 97, no. 4 parasitism of O. nubilalis egg masses was not density Multiple-Crop No-Choice Experiment. In a prelim- dependent, and that T. ostriniae populationswere dis- inary experiment in 2001, we compared T. ostriniae tinctly female biased under Þeld conditions. parasitism in four different crops that were In addition to sweet corn, O. nubilalis isa pest spatially isolated from each other by Ͼ50matthe of other vegetable crops, including beet, cowpea, egg- Cornell University Entomology Research Farm in plant, lima , pepper, potato, snap bean, swiss Freeville, NY. The cropsincluded: sweetcorn (a mix- chard, and tomato (Capinera 2001). In pepper, ture of ÔSprintÕ, ÔDynamoÕ, and ÔBonusÕ planted on O. nubilalis larvae tunnel into and feed on fruit, caus- 1 June with 0.9-m row spacing); potato (a mixture of ing direct damage, premature ripening, and entry ÔAtlanticÕ and ÔSeneca GoldÕ planted in mid-May on pointsfor fruit-rotting pathogens(Hazzard and four-row strips); melon (ÔAthenaÕ cantaloupe set on Ghidiu 2001). If control measures are not taken in black plastic with drip irrigation); and sweet pepper (a pepper, the percentage of damaged fruit can exceed mixture of ÔBoyntonÕ and ÔPaladinÕ also set on black 40Ð60% in (Welty 1995) and Virginia (Kuhar plastic with drip irrigation). Plant surface area was not and Speese 2002, Kuhar et al. 2003b). The is assessed. On 1 August, all crops were producing fruit, difÞcult to control because larvae are only exposed to and we released 1000 T. ostriniae in each of four sep- insecticide sprays from egg hatch until tunneling. In arate 0.01-ha plotsof each crop. Releasecartonswere many regions, effective protection of fruit is only fastened to plant stems in the Þeld by using ßagging achieved with multiple insecticide applications begin- tape. We obtained egg masses of O. nubilalis on wax ning at early fruiting (Welty 1995, Hazzard and Ghidiu paper from a colony at Cornell University and made 2001). sentinels by cutting around a section containing two In potato, O. nubilalis larvae damage the plant by or three egg masses and gluing them to a 2- by 5-cm tunneling near the base of stems causing breakage and strip of wax paper. We pinned 20 O. nubilalis sen- lodging and entry pointsfor stemrot pathogenssuch tinelsto the undersidesofleaveswithin 20 m from as Erwinia carotova (Kennedy 1983). Nault and each release point. We collected sentinels on 3 and Kennedy (1996) showed that O. nubilalis larvae exit 6 August. Collected sentinels were carefully removed and reenter a potato stem an average of 4.7 times from the wax paper, placed in size 00 gelatin capsules, during their development. In most cases, the potato and held in the laboratory at room temperature where plant can tolerate low-to-moderate levelsof insect they were observed daily for parasitism. Because tunneling without impacting tuber yield (Nault et al. plantingsof each crop were not replicated, data were 1996, 2001). However, over the past 5 yr, pest pressure not compared among crops. However, means and from O. nubilalis hasincreasedin potato in Maine and standard errors of percentage of parasitism were cal- other regionsbecausegrowersare no longer ap- culated to show the potential of T. ostriniae to Þnd and plying broad-spectrum foliar insecticides to control parasitize eggs of O. nubilalis in different crops. potato beetle, Leptinotarsa decimlineata Multiple-Crop Choice Experiment. Also in 2001, at (Say) (Coleoptera: Chrysomelidae) (E.G. and T.P.K., the same research farm, we compared parasitism of unpublished data). Potato growers in O. nubilalis among cropsplanted together. Sweet and Virginia routinely apply one to two foliar sprays of corn, pepper, snap bean, and broccoli were arranged insecticides each year solely for O. nubilalis control in four randomized complete blocks, with each sep- (Nault and Kennedy 1996, Nault and Speese 2000). arated by Ͼ300 m to avoid parasitoid movement Given the success of T. ostriniae in sweet corn, there among blocks.Each block was20 rows(0.9 m apart) isinterestin itspotential to control O. nubilalis in by 20 m, and each crop occupied 10 rowsby 10 m in peppersand potatoes.The objectivesof thisstudy a corner of the block. In early June 2001, we direct were to assess the ability of T. ostriniae to locate and seeded a mixture of ÔPrimetimeÕ and ÔSprintÕ sweet parasitize O. nubilalis eggsin cropsother than corn corn and ÔHystyleÕ snap bean. Approximately 2 wk and to evaluate the efÞcacy of inundative releases of later, we set transplants of ÔBoyntonÕ pepper and the parasitoid in pepper and potato. ÔSouthern CometÕ broccoli in the Þeld. On 13 August, we estimated total plant surface area of each crop within a block by measuring leaf and stem area from Þve randomly selected and multiply- Materials and Methods ing by the number of plantswithin the block. Alsoon Before use in these studies, we reared T. ostriniae 13 August, we released Ϸ5,000 T. ostriniae femalesinto for four generationson O. nubilalis and then onto the center of each block at the juncture of the four E. kuehniella for mass production following the meth- crops. On 13, 17, and 21 August, we pinned O. nubilalis ods of Morrison (1985). The were main- egg masssentinelstothe undersidesofleaveson 25 tained at Cornell University, Ithaca, NY, under con- randomly selected plants of each crop per block. After ditionsof 25 ЊC/23ЊC; Ϸ80% RH, and a photoperiod of 3 d in the Þeld, we collected the sentinels and assessed 16:8 (L:D) h with access to undiluted honey (Hoff- for parasitism as described in the previous study. We mann et al. 2001). For all experiments, we used release used analysis of variance (ANOVA) (PROC GLM, containersmade from 150-ml cone-shapedpaper cups SAS Institute 1999) to analyze differences in plant that contained parasitized E. kuehniella eggs. Release surface area and proportion of parasitism. Proportion cartons were stapled shut and perforated to allow parasitism data were arcsine square-root transformed T. ostriniae emergence. before analysis to stabilize variance (Ott 1984). Dif- August 2004 KUHAR ET AL.: T. ostriniae IN SOLANACEOUS CROPS 1211

ferences in percentage parasitism among crops were tested using FisherÕs least signiÞcant difference (LSD) at the ␣ Ͻ 0.05 level of signiÞcance. Evaluations in Pepper. We conducted an experi- ment at sixlocationsin 2002 and three locationsin 2003 (Table 1). Each location represented a replicate in the experiment. We established T. ostriniae release and nonrelease plots (each Ϸ0.02 ha and Ϸ300 plants) of bell pepper at each location. Release and nonrelease plots were separated by at least 200 m. No insecticides were applied to pepper plots. We made four or Þve separate releases of Ϸ30,000Ð50,000 T. ostriniae per release plot (Table 1). Release densities varied some- what on each date because of differences in per- centage of emergence of the parasitoids. Beginning on the day of Þrst release until last harvest, we in- spected 50Ð100 plants approximately weekly in each plot for O. nubilalis egg masses. Egg masses were collected from the Þeld, placed in gel caps(size00), and held at room temperature in the laboratory until release dates Harvest dates O. nubilalis eclosion or emergence of adult parasitoids. Pepperswere hand harvestedand evaluated for damage in August and September (Table 1). At each

T. ostriniae harvest, we inspected a sample of 100 fruit per plot for

17, 23, 30 July, and 6, 22 Aug.11, 24 July, and 7, 14, 16 30 Aug. Aug.15, 26 July, and 6, 13, 29 Aug. 24 July, 7, 14, 21, 27 Aug. and 6, 3, 15,30 10, 20, July, 17 30 and Sept. Aug., 6, and 12 5, and 12, 19 18 Aug. Sept. 15, 25 Aug., and 9insect and 24 Sept. injury. We dissected any infested fruit and re- corded the number of O. nubilalis or other insect larvae present. We pooled data across years to in- crease the sample size for statistical analysis. We used paired t-tests (SAS Institute 1999) at the P Ͻ 0.05 level of signiÞcance to analyze potential treatment differ- ences in proportion of egg parasitism and cumulative proportion of fruit infested at harvest. Proportion of parasitism data were arcsine square-root transformed before analysis to stabilize variance (Ott 1984). Evaluations in Potato. In 2002, we established T. ostriniae release and nonrelease plots (0.2 ha) of potato at four locations: the Eastern Shore Agricul-

Crop production method tural Research and Extension Center near Painter, VA; two University of Maine Research Farms, RogerÕs Farm in Old Town, ME, and Aroostook Farm in

irrigation irrigation irrigation irrigation Presque Isle, ME; and a commercial farm in Presque Isle, ME. We established and maintained potato crops according to standard grower practices. In Maine, we monitored O. nubilalis activity by using wire cone trapscontaining the “E” and “Z” strain phero-

date mone lures. Beginning at Þrst moth catch (early July), release dates for each location of the pepper experiments in 2002 and 2003 Transplant we sampled 50 random plants per plot each week for O. nubilalis egg masses. Additionally, each week from 15 July to 19 August, we installed Ϸ30Ð100 sentinels in each plot by pinning them to the undersides of ran- T. ostriniae domly selected plants. In Virginia, we did not sample for natural O. nubilalis egg masses, but we did install Ϸ30 sentinels in each plot weekly from 23 May to 12 June. On 22 May and 12 June in Virginia, and 15 and 22 July in Maine, we released 75,000 T. ostriniae per plot. We collected O. nubilalis sentinels and natural egg masses weekly and assessed for parasitism as de- scribed above. In 2003, we established T. ostriniae release and non-

Location Variety release plots (0.2 ha) of potato at Þve locations: four

Table 1. Crop information and commercial Þelds near Cape Charles, VA, and Aroos- Eastern Shore 1, VAEastern Shore 2, VATidewater, VA ÔPaladinÕ ÔPaladinÕ ÔPaladinÕ 18 June 18 JuneEastern Shore, VAVirginia Beach, VA GroundSouth 19 with DeerÞeld, June overhead MA irrigation Ground with overhead irrigation ÔPaladinÕ ÔPaladinÕ ÔAristotleÕ Single rowson black plasticwith drip-line 18 June 24 June 4 June 17, 23, 30 Ground July, 17, with and 23, overhead 6, Ground 30 irrigation 22 with July, Double-staggered Aug. drip-line and rows irrigation 6, on 22 black Aug. plastic with drip 16 Aug. and 10 16 Sept. Aug. and 10 Sept. 16, 23, 30 July, 16, and 23, 6 30 Aug. July, and 6 Aug. 14, 21 Aug., and 12, 2 20 Sept. Aug., and 1, 9 Sept. Virginia Beach, VALandisville, PARock Springs, PA ÔPaladinÕ ÔKing ArthurÕ ÔKing ArthurÕ 18 June 3 June 10 June Ground with drip-line irrigation Double-staggered rows on black Double-staggered plastic rows with on drip black plastic with drip 17, 23, 30 July, and 6, 22 Aug. 16 Aug. and 4 Sept.

2002 2003 took Farm in Presque Isle, ME. We sampled for natural 1212 JOURNAL OF ECONOMIC ENTOMOLOGY Vol. 97, no. 4

Fig. 2. Percentage of O. nubilalis sentinel egg masses parasitized (ϮSE) after a single release of 5,000 T. ostriniae Fig. 1. Parasitism of sentinel O. nubilalis egg masses into a 0.02-ha block of four vegetable cropsat Freeville, NY. Ϯ Bars with the same letter are not signiÞcantly different, Fish- ( SE) after simultaneous releases of 1000 T. ostriniae into Ͻ replicated plotsof four vegetable cropsspatiallyisolatedfrom erÕsprotected LSD, P 0.05. each other near Freeville, NY. ϭ ϭ O. nubilalis egg masses by examining 100 plants per occurred among the cropsa t4d(F 4.09; df 3, 15; Ͻ ϭ ϭ Ͻ plot on 3 and 10 June in Virginia and 7 and 30 July in P 0.05),7d(F 4.13; df 3, 15; P 0.05), and 10 d ϭ ϭ Ͻ Maine to assess for parasitism. On 14 May and 5 June (F 8.34; df 3, 15; P 0.05) after T. ostriniae release. in Virginia and 17 and 24 July in Maine, we released Parasitism was signiÞcantly higher in sweet corn than 75,000 T. ostriniae per plot. other crops, followed by pepper, snap bean, and then In mid-June in Virginia and in late August in Maine broccoli (Fig. 2). of both years, before potato plants dried down, we Evaluations in Pepper. In 2002, heavy pest pressure examined 200 randomly selected potato stems per plot from O. nubilalis occurred at all four Virginia locations for signs of O. nubilalis infestation. We dissected any and moderate pressure occurred at the Pennsylvania stemswithtunnelsand counted O. nubilalis larvae locations (Fig. 3). In 2003, low-to-moderate pest pres- present. We pooled data across years to increase the sure from O. nubilalis occurred at all three locations. sample size for statistical analysis. We used paired Very little (1.9 Ϯ 1.6%) parasitism occurred in t-tests (SAS Institute 1999) at the P Ͻ 0.05 level of O. nubilalis egg masses collected from nonrelease signiÞcance to analyze potential treatment differences (control) plots, whereas 48.7 Ϯ 6.8% of the egg masses in number of stemswithtunnelsand number of collected from release plots were parasitized by O. nubilalis larvae per 200 stems. T. ostriniae (Table 2). Thisdifference in parasitization washighly signiÞcant( t ϭ 8.54, df ϭ 8, P Ͻ 0.0001). At harvest, the percentage of fruit damaged averaged Results 27.3 Ϯ 6.3% in nonreleaseplotsand wassigniÞcantly Multiple-Crop No-Choice Experiment. At 3 d after lower (t ϭ 4.17, df ϭ 8, P ϭ 0.0031) in release plots, T. ostriniae were released, parasitism of O. nubilalis egg averaging 8.7 Ϯ 1.6% (Table 2). Of the found masses was low in all crops, and the only sentinel egg in pepper fruit, 95% were identiÞed as O. nubilalis. The masses that were parasitized were collected from the remaining 5% were the noctuid pests, sweet corn plots (Fig. 1). At 6 d after release, parasitism (Boddie), exigua Hu¨ bner, Spodoptera fru- of O. nubilalis egg masses was detected in the sweet corn, giperda (J.E. Smith), and Spodoptera ornithogalli pepper, and potato plots, with sweet corn having a much (Guenee´) or pepper maggot, Zonosemata electa (Say) higher parasitism than all other crops. (Diptera: Tephritidae). Multiple-Crop Choice Experiment. On the date of Evaluations in Potato. In both years, very few nat- release of T. ostriniae, total plant surface area was ural O. nubilalis egg masses were encountered in the different among crops( F ϭ 17.4; df ϭ 3, 15; P Ͻ 0.001), potato plotsand sentinelshadvery little ( Ͻ1%) par- with sweet corn having the greatest surface area asitism. Thus, parasitism data were not analyzed. The (167.6 Ϯ 25.3 m2), followed by snap bean (118.7 Ϯ number of potato stems damaged by O. nubilalis was 6.3 m2), and then broccoli (41.0 Ϯ 2.2 m2) and pepper signiÞcantly less in T. ostriniae release plots (t ϭ 3.00, (32.7 Ϯ 1.8 m2), which did not differ from each other. df ϭ 8, P ϭ 0.0171; Table 3). Similarly, the number of Differences in parasitism of O. nubilalis egg masses O. nubilalis larvae per 200 stems was signiÞcantly less August 2004 KUHAR ET AL.: T. ostriniae IN SOLANACEOUS CROPS 1213

Fig. 3. Total numbersof O. nubilalis egg masses (represented by the black diamond) and egg masses parasitized by T. ostriniae (represented by open square) in release and control plots of pepper in 2002 from the following locations: (A) Landisville, PA; (B) Rock Springs, PA; (C) Tidewater, VA; (D) Virginia Beach, VA; (E) Eastern Shore 1, VA; and (F) Eastern Shore 2, VA. 1214 JOURNAL OF ECONOMIC ENTOMOLOGY Vol. 97, no. 4

Table 2. European corn borer egg parasitization and damage to sweet pepper with and without inundative releases of T. ostriniae

% parasitization of total % cumulative harvested Location collected ECB egg masses fruit damaged by ECB Release Control Release Control 2002 Eastern Shore 1, VA 54.9 0.3 14.0 53.0 Eastern Shore 2, VA 56.7 2.6 18.0 65.5 Tidewater, VA 52.1 0.0 9.0 19.0 Virginia Beach, VA 46.3 0.0 5.5 26.0 Landisville, PA 12.5 0.0 8.5 20.6 Rock Springs, PA 20.0 0.0 3.6 16.7 2003 Eastern Shore, VA 58.1 0.0 8.4 14.2 Virginia Beach, VA 60.9 0.0 8.5 13.3 South DeerÞeld, MA 76.9 14.3 3.2 17.2 Mean Ϯ SE 48.7 Ϯ 6.8% 1.9 Ϯ 1.6%a 8.7 Ϯ 1.6% 27.3 Ϯ 6.3%a

ECB, European corn borer. a SigniÞcant difference between T. ostriniae release and control according to paired t-test (P Ͻ 0.05). in T. ostriniae release plots (t ϭ 2.39, df ϭ 8, P ϭ al. 1982, Keller et al. 1985, Thorpe 1985). Some host 0.0439). plantsprovide volatile cues(kairomones)that arrest and stimulate searching and parasitism in Tri- chogramma (Altieri et al. 1982, Noldus1989). More Discussion research into the environmental cues (visual and Smith (1996) suggested that Trichogramma Þnd chemical) used by T. ostriniae for host Þnding is host eggs by random searching, and authors have hy- needed to help explain these differences. pothesized that parasitism is inversely proportional to Although dicotyledonousplantsmay not be the the size(Ableset al. 1980, Burbutisand Koepke 1981, preferred habitat or most efÞcient habitat for Þnding Wang et al. 1997) and complexity (Andow and hosts, our study showed that four to Þve inundative Prokrym 1990, Gingrasand Boivin 2002) of the host releases of T. ostriniae in pepper resulted in signiÞcant plant. In general, the greater the plant surface area to O. nubilalis egg parasitism and concomitant reduc- search, the lower the parasitism rate. In our multiple- tionsin fruit damage. Pepper fruit damage averaged crop experiments, however, sweet corn had the great- 8.7% in our T. ostriniae release plots, which is compa- est plant surface area, yet the highest parasitization of rable with peppers sprayed up to six times with stan- O. nubilalis egg masses by T. ostriniae. Plant complex- dard insecticides such as acephate, spinosad, methoxy- ity may have been a factor, with corn having a fairly fenozide, indoxacarb, or pyrethroids(Kuhar and simple monocotyledonous architecture with rela- Speese 2002, Kuhar et al. 2003b). Moreover, in pota- tively few connections of leaves, buds, and stems (Gin- toes, two releases of Ϸ75,000 T. ostriniae per 0.2 ha gras and Boivin 2002). Nonetheless, we believe that signiÞcantly reduced the number of tunnel holes and our results suggest a habitat selection or preference by number of O. nubilalis larvae in potato stems. Based on T. ostriniae for corn over dicotyledonousplants.Smith our knowledge of the scientiÞc literature, these results (1996) suggested that Trichogramma species, in gen- demonstrate one of the most efÞcacious uses of a eral, are much more habitat speciÞc than host speciÞc. parasitoid to control O. nubilalis in peppersor pota- Thishasbeen demonstratedin Trichogramma pretio- toes. Working with a similar species, Trichogramma sum Riley and Trichogramma minutum Riley (Altieri et nubilale Ertle & Davis, in sweet pepper in ,

Table 3. European corn borer damage in potato fields in Maine and Virginia with and without inundative releases of T. ostriniae

No. tunnel holes/200 stems No. O. nubilalis larvae/200 stems Location T. ostriniae release Control T. ostriniae release Control 2002 Aroostook Farm, Presque Isle, ME 74 125 62 104 RogerÕsFarm, Old Town, ME 4 28 10 18 Commercial Farm, Presque Isle, ME 31 67 31 67 Eastern Shore, VA 16 12 8 4 2003 Aroostook Farm, Presque Isle, ME 80 100 54 67 Cape Charles1, VA 22 19 13 11 Cape Charles2, VA 10 10 4 4 Cape Charles3, VA 5 46 5 26 Cape Charles4, VA 4 19 3 8 Mean Ϯ SE 27.3 Ϯ 9.9 47.3 Ϯ 13.9a 21.1 Ϯ 7.5 34.3 Ϯ 12.0a

a SigniÞcant difference between T. ostriniae release and control according to paired t-test (P Ͻ 0.05). August 2004 KUHAR ET AL.: T. ostriniae IN SOLANACEOUS CROPS 1215

Burbutis and Koepke (1981) achieved 80% parasitism Andow, D. A., and D. R. Prokrym. 1990. Plant structural of O. nubilalis eggswith a releaserate of 12 females complexity and host-Þnding by a parasitoid. Oecologia per plant. Unfortunately, fruit damage wasnot as- (Berl.). 82: 162Ð165. sessed in that study. Also, T. nubilale waslater found Burbutis, P. P., and C. H. Koepke. 1981. European corn to be expensive to mass produce commercially, unlike borer Ostrinia nubilalis control in peppersby Tricho- T. ostriniae (Wang et al. 1999). gramma nubilale. J. Econ. Entomol. 74: 246Ð247. Tolerance for crop injury playsan important role in Capinera, J. L. 2001. Handbook of vegetable pests. Aca- demic, New York. the level of O. nubilalis control required. Potato can Frye, R. D. 1972. Evaluation of insect predation on Euro- withstand reasonable levels of O. nubilalis tunnel in- pean corn borer in North Dakota. Environ. Entomol. 1: jury without signiÞcant yield loss (Nault and Kennedy 535Ð536. 1996, Nault et al. 2001), but tolerance for O. nubilalis Gingras, D., and G. Boivin. 2002. Effect of plant structure, in pepper ismuch lower becausethe marketable por- host density and foraging duration on host Þnding by tion of the crop isdirectly injured (Hazzard and Trichogramma evanescens (Hymenoptera: Trichogram- Ghidiu 2001). Therefore, combined O. nubilalis mor- matidae). Environ. Entomol. 31: 1153Ð1157. tality rates from parasitism and other factors would Hassan, S. A., and M. F. Guo. 1991. Selection of effective need to be higher in pepper than potato for economic strains of egg parasites of the genus Trichogramma (Hym., control. European corn borer eggsand early instars Trichogrammatidae) to control the European corn borer are attacked by naturally occurring predators, parasi- Ostrinia nubilalis Hb. (Lep., Pyralidae). J. Appl. Entomol. toids, and pathogens (Mason et al. 1996). These nat- 111: 335Ð341. Hazzard, R. V., and G. M. Ghidiu. 2001. European corn ural enemiesalong with abiotic factorscontribute to borer management, pp. 67Ð76. In T. J. Boucher and R. A. a relatively high natural mortality (60Ð90%) of O. Ashley [eds.], Northeast pepper integrated pest manage- nubilalis eggsand early instarsincorn (Frye 1972, ment (IPM) manual. Univ. Conn. Coop. Ext., Stoors, CT. Showers et al. 1978, Ross and Ostlie 1990). In sweet Hoffmann, M. P., D. L. Walker, and A. M. Shelton. 1995. corn, Kuhar et al. (2002) showed that 60Ð80% of O. Biology of Trichogramma ostriniae (Hymenoptera: nubilalis eggsand early larvae perishedfrom natural Trichogrammatidae) reared on Ostriniae nubilalis causes and that increasing egg parasitism to 37% with (Lepidoptera: Pyralidae) and survey for additional hosts. augmentative releases of T. ostriniae increased the Entomophaga 40: 387Ð402. total mortality to Ͼ90%. Thisresultedin a concomitant Hoffmann, M. P., P. R. Ode, D. L. Walker, J. Gardner, S. van 50% reduction in ear damage. Nouhuys, and A. M. Shelton. 2001. Performance of Thus, depending on the degree of pest pressure, the Trichogramma ostriniae (Hymenoptera: Trichogramma- tolerance for injury in the host plant and the market, tidae) reared on factitioushostsincludingthe target host, Ostrinia nubilalis (Lepidoptera: Crambidae). Biol. Con- and the level of natural control, T. ostriniae may pro- trol 21: 1Ð10. vide an effective management option for O. nubilalis Hoffmann, M. P., M. G. Wright, S. A. Pitcher, and J. Gardner. in solanaceous crops. More work is needed to optimize 2002. Inoculative releases of Trichogramma ostriniae for release rates and strategies, as well as compatibility suppression of Ostrinia nubilalis (European corn borer) with other management tactics such as insecticides. in sweet corn: Þeld biology and population dynamics. Biol. Control 25: 249Ð258. Keller, M. A., W. J. Lewis, and R. E. Stinner. 1985. 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