Compatibility of Insect Growth Regulators with Eretmocerus eremicus (Hymenoptera: Aphelinidae) for Whitefly (Homoptera: Aleyrodidae) Control on Poinsettias: I. Laboratory Assays

The compatibility of five insect growth regulators (IGRs), buprofezin, pyriproxyfen, fenoxycarb, pymetrozine, and kinoprene, were tested in the laboratory for compatibility with the whitefly parasitoid Eretmocerus eremicus Rose and Zolnerowich (Hymenoptera: Aphelinidae). The survivorship of adult parasitoids foraging on poinsettia leaves with residues 6, 24, and 96 h of age was determined. The toxicity of Bemisia argentifolii Bellows and Perring (Homoptera: Aleyrodidae) patches treated with IGRs presented to female parasitoids 24 and 96 h posttreatment was quantified. Survivorship of immature E. eremicus developing within B. argentifolii nymphs was determined by treating whitefly nymphs with IGRs 5 and 13 days postoviposition by female parasitoids. Finally, behavioral observations of female parasitoids foraging on IGR-treated and untreated B. argentifolii patches presented simultaneously were quantified to determine whether IGR residues had a repellant effect toward E. eremicus. Averaging ranks for IGRs based on their compatibility with E. eremicus and their ability to kill B. argentifolii nymphs produced the following parasitoid compatibility order: buprofezin > fenoxycarb > pymetrozine = pyriproxyfen > kinoprene. Further work in greenhouses assessing the efficacy of buprofezin with E. eremicus for B. argentifolii control on poinsettias is recommended.     

Effects of selected insecticides on Diadegma semiclausum（Hymenoptera： Ichneumonidae） and Oomyzus sokolowskii （Hymenoptera： Eulophidae）, parasitoids of Plutella xylostella （Lepidoptera： Plutellidae）

Abstract Field doses of six selected insecticides were tested against the immature (pupae) and mature (adult) stages of Diadegma semiclausum (Hellén) and Oomyzus sokolowskii (Kurdjumov), parasitoids of the diamondback moth, Plutella xylostella (L.). Effects of contact toxicity (direct spraying) of the six insecticides on emergence of parasitoids were found negligible on both species except permethrin which caused 37.5% mortality. All adults of both parasitoid species died 24 hours after exposure to chlorfenapyr, emamectin benzoate and permethrin. In contrast, the three insect growth regulators (IGRs), chlorfluazuron, flufenoxuron and teflubenzuron, were found harmless to both species, and adult mortality of both parasitoid species was 0–16.7%. However, parasitism by the females of both parasitoid species was severely impaired when the females were offered the three IGR diluted solutions for 24 hours. Effects of oral toxicities of the IGRs on longevity of both parasitoids after 12 hours exposure were found to be significantly different between males and females. Compatibility of tested insecticides with D. semiclausum and O. sokolowskii and integration of compatible insecticides with these parasitoids in integrated pest management programs of crucifers are discussed.     

Effects of pirimicarb,buprofezin and pymetrozine on survival,development and reproduction of Coccinella undecimpunctata (Coleoptera: Coccinellidae)

The effects of pirimicarb (a neurotoxin), buprofezin (an insect growth regulator) and pymetrozine (an antifeedant) on Coccinella undecimpunctata were assessed by studying the survival and development of all immature stages and the survival and reproductive performance of adults. Insecticides were sprayed at doses recommended by the manufacturers for the control of aphids and/or whiteflies. None of the three insecticides had a significant effect on the survival of C. undecimpunctata eggs. When sprayed on larvae, buprofezin significantly reduced survival to adulthood to <33%, compared to >45% for the control and other insecticide treatments. Rates of adult survival, fecundity, and fertility, and the percentage of egg hatch, were not significantly different between control and insecticide treatments. Thus, larval stages were more susceptible to insecticides than were adults. In general, pirimicarb and pymetrozine had no adverse effects on immature or adult stages of C. undecimpunctata, and hence are suitable for IPM of sucking pests.     

Selectivity evaluation of insecticides used to control tomato pests to Trichogramma pretiosum

The effects of the insecticides abamectin, acetamiprid, cartap and chlorpyrifos on larvae, pupae (within the host egg) and adults of the egg parasitoid Trichogramma pretiosum Riley (Hym.: Trichogrammatidae) were evaluated under laboratory conditions, using three standard tests described by IOBC. When sprayed on the immature stages of this parasitoid, cartap and chlorpyrifos proved to be the most harmful insecticides, affecting both the emergence success and parasitism capacity of this parasitoid, whereas abamectin and acetamiprid were selective. Abamectin was harmful to adults (residue test on glass plates), slightly harmful to larvae, and moderately harmful to pupae (sprayed on the immature stages within host eggs Anagasta kuehniella (Zeller)); acetamiprid was moderately harmful to adults, harmless to larvae, and slightly harmful to pupae; cartap was harmful to adults, moderately harmful to larvae and harmful to pupae; chlorpyrifos to adults, harmless to larvae and harmful to pupae.     

Effects of selected insecticides on Cotesia plutellae, endoparasitoid of Plutella xylostella

Effects of field dosages ofselected insecticides to Cotesiaplutellae (Kurdjumov) (Hymenoptera: Braconidae), a larval endoparasitoidof Plutella xylostella L. (Lepidoptera: Plutellidae), wereinvestigated under laboratory conditions.Emergence of adult C. plutellae frominsecticide-treated pupae was not significantlydifferent from the control treatment. Contacttoxicity to C. plutellae adults variedgreatly among the insecticides in a paperresidue contact bioassay. Threeazadirachtin-based insecticides, Agroneem(4.8 mg a.i.liter^–1), Neemix (20 mga.i.liter^–1) and Ecozin (20 mgai.liter^–1) caused 11.1, 16.7 and 5.6%adult mortality, respectively. Of fourcommercial Bacillus thuringiensis (Bt)insecticides examined (all at 1.2 mga.i.liter^–1), Crymax and Xentari had noeffect on adult parasitoids, whereas Mattchcaused 5.6% mortality, and Dipel caused 11.1%mortality. Indoxacarb (53 mg a.i.liter^–1),-cyhalothrin (28 mg a.i.liter^–1) andspinosad (53 mg a.i.liter^–1) caused 100,88.5 and 50% adult mortalities, respectively.Low adult mortality (0–5.6%) was recorded fromingestion of azadirachtin-based, Btinsecticides and indoxacarb, compared with100% adult mortality in treatments of spinosador -cyhalothrin. Compared with the watercontrol, ingestion of azadirachtin-basedinsecticides significantly reduced parasitismby 50–57%, and Bt insecticides by 8–25%.However, ingestion of these insecticides didnot affect longevity of male and femaleparasitoid adults with one exception; femalelongevity was significantly reduced in theindoxacarb treatment. Insecticide residuescaused considerable mortality of C.plutellae adults, 39 and 44% mortality causedby 10 d old indoxacarb and -cyhalothrin,respectively, and 24 and 0% mortality causedby 7 and 10 d old residues of spinosad,respectively.     

三种杀虫剂对烟粉虱优势寄生蜂海氏桨角蚜小蜂的安全性评价

为评价噻虫嗪、阿维菌素和氟啶虫胺腈对烟粉虱优势寄生蜂海氏桨角蚜小蜂Eretmocerus hayati的安全性,采用琼脂保湿浸叶法分别测定了3种杀虫剂对烟粉虱成虫和海氏桨角蚜小蜂成蜂的室内毒力以及对海氏桨角蚜小蜂蛹羽化率的影响.结果表明,噻虫嗪、阿维菌素和氟啶虫胺腈对烟粉虱的LC50分别为453.76 mg/L、2.00 mg/L和29.47 mg/L,对海氏桨角蚜小蜂成蜂的LC50分别为0.23 mg/L、1.07 mg/L和0.64 mg/L.通过风险系数评估,表明阿维菌素对海氏桨角蚜小蜂成蜂安全,而噻虫嗪和氟啶虫胺腈对该蜂成蜂具有轻微到中度毒性.3种杀虫剂在烟粉虱和寄生蜂之间的选择性毒力指数表明噻虫嗪对海氏桨角蚜小蜂的负向选择性最强,其次是氟啶虫胺腈,阿维菌素最弱.3种杀虫剂均可显著降低海氏桨角蚜小蜂蛹的羽化率,对蛹的毒性为轻微有害,风险等级为2级.本研究结果将为烟粉虱综合治理中协调使用寄生蜂和化学药剂奠定理论基础.     

Yellow sticky trap catches of parasitoids of Bemisia tabaci (Hemiptera: Aleyrodidae) in vegetable crops and their relationship to in-field populations

We examined the relationship of yellow sticky trap captures of Bemisia tabaci (Gennadius) biotype B parasitoids to the local population of parasitoids as measured by leaf samples of parasitized whiteflies and mass release of parasitoids. Traps were placed in experimental collard and cowpea field plots in Charleston, SC, and in commercial organic fields of spring cantaloupe and watermelon in the Imperial Valley, CA. The exotic parasitoid Eretmocerus emiratus Zolnerowich and Rose was released in Imperial Valley fields to ensure parasitoid populations would be present. Bemisia adults were trapped in the greatest numbers on the upper surface of horizontally oriented sticky traps in melon fields. In contrast, the lower trap surfaces consistently captured more Eretmocerus than upper surfaces. Female parasitoids were trapped in greater numbers than males, especially on the lower trap surfaces. Progeny of released exotic Eretmocerus greatly outnumbered native E. eremicus Rose and Zolnerowich and Encarsia spp. on traps. Throughout the season, the trend of increasing numbers of Eretmocerus on traps parallelled the increase in numbers of whiteflies. Over the season, 23-84% of all B. tabaci fourth instars were visibly parasitized by Eretmocerus. The numbers of Eretmocerus caught by traps in cantaloupe were similar in trend to numbers on leaf samples in melons, but not with those in watermelon, where whitefly populations were lower. Parasitoid numbers were low in collard and cowpea samples, and no trend was observed in numbers of parasitoids captured on traps and numbers on leaves for these two crops. Overall, there were no significant correlations between sticky trap catches of parasitoids and numbers of parasitized whiteflies on leaf samples in any test fields. Nevertheless, sticky traps placed within crops may be useful for observing trends in whitefly parasitoid populations at a particular site and for detecting parasitoids at specific locations.     

Effects of selected insecticides on adults of two parasitoid species of Liriomyza trifolii: Ganaspidium nigrimanus (Figitidae) and Neochrysocharis formosa (Eulophidae)

Abstract Liriomyza trifolii is an important pest of vegetables and ornamental crops around the world. This pest is attacked by many parasitoid species. The principal management tactic used against L. trifolii is insecticide application. Insecticides vary in their effects on parasitoid species and insecticides that have less harmful effects should be preferred for the control of this pest. In this study, novaluron, abamectin, λ‐cyhalothrin and spinetoram were investigated for their lethal effects on adults of Neochrysocharis formosa and Ganaspidium nigrimanus, two important parasitoids of L. trifolii. Three different bioassays were used on adult parasitoids: direct insecticide application, insecticide intake and insecticide residue. Adult parasitoid response to novaluron exhibited the least lethal effects among the bioassays and insecticides tested. Abamectin had significant mortality to both parasitoid species in the direct application and insecticide intake bioassays and mortality were high for G. nigrimanus in the residue bioassay. Spinetoram was the most harmful insecticide to the adult parasitoids in all three bioassays. λ‐cyhalothrin effects varied between the two parasitoids. In the direct application, it was harmful to G. nigrimanus and had no effect on N. formosa. In the insecticide intake bioassay λ‐cyhalothrin had no effect in survival of either species, and in the residue bioassay it reduced parasitoid survival of both species. Potential tolerance of N. formosa to λ‐cyhalothrin is discussed.     

Field Evaluation of Amitus bennetti (Hymenoptera: Platygasteridae), a Parasitoid of Bemisia argentifolii (Hemiptera: Aleyrodidae), in Cotton and Bean

Field cage experiments were conducted in Riverside, California to quantify the impact of releases of the parasitoid Amitus bennetti Viggiani & Evans on mortality of the whitefly Bemisia argentifolii Bellows & Perring. Single-row 50-m-long plots were planted with either cotton or bean. Cages were erected over the plants in each row, and adult whiteflies were released into the cages. Approximately 10 days later, adult parasitoids were released. Marked individual whiteflies were scored every 4 days for 6 weeks. Paired life tables were then constructed from census data from release and control cages over a single whitefly generation. Total whitefly mortality in release cages (71% in bean, 61% in cotton) was significantly greater than in control cages (25% in bean, 34% in cotton). The marginal rate for mortality attributable directly to the parasitism was 0.535 in the bean plots and 0.201 in the cotton plots. In addition, other mortality was greater in the release plots, possibly reflecting death of parasitized hosts before larval parasitoids could complete development. Parasitism was the greatest mortality factor in the study.     

The prospect of using sub-lethal imidacloprid or pirimicarb and a parasitoid wasp, Lysiphlebus fabarum, simultaneously,to control Aphis gossypii on cucumber plants

The broad-spectrum insecticides greatly influence the control of cotton aphids; however, due to frequent chemical control, Aphis gossypii (Hemiptera: Aphididae) has developed resistance against several classes of synthetic insecticides. In this study, we explored the sub-lethal effects of imidacloprid and pirimicarb, two commonly used insecticides for aphid control, on a parasitoid wasp, Lysiphlebus fabarum (Marshall) (Braconidae: Aphidiinae), when simultaneously used to control melon aphid on cucumber plants, as part of a comprehensive study for integrated pest management. Bioassays of imidacloprid and pirimicarb were performed to calculate LC₅₀ with third instars of A. gossypii. The LC₅₀ of these insecticides (110.55 and 250.89 μg/lit, respectively) were used to expose the wasp larvae, pupae, and adult parasitoids on a cucumber leaf. The percent mortality, percent adult emergence, and sex ratio were calculated during each exposure test. Moreover, the body size, egg load, and mature egg size of wasps surviving the insecticide treatments, as well as the sex ratio of the second generation was evaluated. Regardless of the host aphid mortality, none of the insecticides caused mortality of larval stage of the parasitoid. The insecticide application on pupal stage revealed that the percentage of mortality, sex ratio, body size, and egg load of surviving wasps, as well as the sex ratio of their offspring was adversely affected by imidacloprid, but not by pirimicarb. The present study suggests pirimicarb as a preferred insecticide, with less harmful effects on the fitness components of L. fabarum, for integrated pest management of cotton aphids.     

Limited protection of the parasitoid Pachycrepoideus vindemiae from Drosophila suzukii host‐directed spinosad suppression

Laboratory trials were conducted to determine whether the spotted wing drosophila, Drosophila suzukii (Matsumura) (Diptera: Drosophilidae), puparium can provide an effective physical barrier to protect immature stages of the pupal parasitoid Pachycrepoideus vindemiae (Rondani) (Hymenoptera: Pteromalidae) from spinosad treatments. Spinosad insecticides are currently an important suppression strategy for D. suzukii in organically managed fruit orchards although they are well known to cause mortality in hymenopteran parasitoids. High adult P. vindemiae female mortality (83%) occurred within 24 h of exposure to D. suzukii pupae treated with 10 mg a.i. l^?1 spinosad and female parasitoids did not avoid the pupae treated with similar low levels of spinosad in choice tests that included untreated pupae. Pachycrepoideus vindemiae develops as an idiobiont ectoparasitoid on host fly pupa within the sclerotized host puparium. Significant P. vindemiae survival and emergence was recorded when parasitized D. suzukii puparia were exposed to field treatment levels of spinosad; however, the parasitoid survival was dependent on the time of the spinosad treatment of the host post‐parasitization. Significant parasitoid survival occurred when the host puparia were treated at 2 weeks when the parasitoid was in the pupal stage but did not occur when the host puparia were treated at 1 week post‐parasitization, when the parasitoids were still in a larval stage. The parasitoid adults consumed or otherwise came in contact with residual degrading spinosad when they exited the treated host, and consequently high and low adult parasitoid mortality occurred when the adults emerged from puparia treated at 2 and 1 week(s), respectively. Our study indicates that generally the integration of P. vindemiae parasitism into a sustainable D. suzukii management program is not compatible with spinosad treatments, although P. vindemiae in the pupal stage inside sclerotized host puparia appear to be minimally impacted by spinosad treatments, provided that the spinosad degrades before parasitoid emergence.     

Intraguild predation of Serangium parcesetosum (Coleoptera: Coccinellidae), on whitefly Bemisia tabaci (Homoptera: Aleyrodidae) parasitized by Eretmocerus mundus (Hymenoptera: Aphelinidae)

We studied intraguild predation of Serangium parcesetosum on Eretmocerus mundus, both natural enemies of Bemisia tabaci, on eggplant under laboratory conditions. Fourth instar and adult predators attacked parasitized and unparasitized hosts equally if immature parasitoids were larvae, but avoided predating on parasitized hosts containing pupae.     

Physiological susceptibility of the predator Macrolophus basicornis (Hemiptera: Miridae) to pesticides used to control of Tuta absoluta (Lepidoptera: Gelechiidae)

In order to aid the integration of biological and chemical controls for the tomato leaf miner, Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae), this study evaluated the relative toxicity of five insecticides to the leaf miner predator Macrolophus basicornis (Stal) (Hemiptera: Miridae). The insecticides evaluated were teflubenzuron, abamectin, chlorantraniliprole, chlorfenapyr, and cartap hydrochloride, all of which are recommended for control of T. absoluta in Brazil. Nymphs and adults of M. basicornis were exposed to tomato leaves treated with the insecticides, under laboratory and greenhouse conditions. The overall mortality caused by the products in both situations was recorded, and the survival of congeneric groups was analysed using the Weibull model. The persistence of the insecticides was also evaluated and they were categorised into toxicity classes proposed by the International Organisation for Biological Control (IOBC) based on predator mortality and persistence. Abamectin and chlorfenapyr were toxic to M. basicornis nymphs and adults in all bioassays. Cartap hydrochloride was slightly harmful to adults in laboratory assays, but harmful to nymphs, and moderately harmful under greenhouse conditions. Chlorantraniliprole and teflubenzuron were harmless in most assays, except when nymphs were exposed in the laboratory, where they were moderately and slightly harmful, respectively. Chlorantraniliprole and teflubenzuron should be preferred insecticides for use in tomato leaf miner IPM programmes that aim to conserve M. basicornis populations.     

Compatibility of Chemical Disease and Insect Management Practices Used in New York Vineyards with Biological Control by Anagrus spp. (Hymenoptera: Mymaridae), Parasitoids of Erythroneura Leafhoppers

Toxicity to Anagrus spp. of fungicides and insecticides used in grape production was assessed with laboratory and field bioassays. Field-equivalent rates of fungicides were relatively nontoxic to Anagrus spp. adults in laboratory bioassays. In bioassays with field-weathered residues, sulfur (9600 ppm) caused elevated mortality of adults for 14 to 21 days posttreatment. Residues of microencapsulated methyl parathion (600 and 1200 ppm) increased mortality relative to the control up to 43 days posttreatment. Duration of elevated mortality of adults exposed to carbaryl was dose dependent and ranged from 14 (at 1200 ppm) to >43 days (at 4800 ppm). Residues of carbaryl and methyl parathion applied over parasitized eggs had little effect on emergence, but may have delayed development. In a field trial, adults trapped in carbaryl-treated plots were significantly reduced starting 3 weeks after treatment. Subsequent lower trap catches may have been related to effects of residues on Anagrus spp. adults or to lower leafhopper egg densities in treated plots.     

Lethal and sub-lethal effects of insecticides on natural enemies of citrus scale pests

Laboratory trials were conducted to test the side-effects of the insecticides chlorpyrifos-methyl, buprofezin, pyriproxifen, spinosad and a narrow range mineral oil on Aphytis melinus DeBach, Coccophagus lycimnia Walker (Hymenoptera: Aphelinidae) and Leptomastix dactylopii Howard (Hymenoptera: Encyrtidae). The effects of chlorpyrifos-methyl, spinosad and pyriproxifen were also investigated in semi-field conditions on L. dactylopii. Contact toxicity on adult female parasitoids after 24, 48 and 72 h, the effects on their fertility as well as the sex ratio of the progeny were measured. In the laboratory trials chlorpyrifos-methyl and spinosad caused 100% mortality on all tested parasitoids just 24 h after the treatment. According to the IOBC classification, the mineral oil was slightly harmful on L. dactylopii; buprofezin was harmful on C. lycimnia, and slightly harmful on L. dactylopii and A. melinus; pyriproxifen resulted moderately harmful on C. lycimnia and slightly harmful on L. dactylopii and A. melinus. The progeny production of each L. dactylopii surviving female treated with buprofezin was not affected by the treatment while in the case of A. melinus it was significantly reduced. C. lycimnia females treated with pyriproxifen did not produce any progeny. In semi-field conditions the tested insecticides were less harmful to L. dactylopii adults but, although none of them influenced the progeny production of the survived females, the longevity was negatively affected.     

Pesticidal effects on mortality and parasitismrates of Diadegma semiclausum, aparasitoid of the diamondback moth

The contact and oral toxicity of fielddoses of selected pesticides against the cocoon andadult stages of a hymenopterous parasitoid Diadegma semiclausum were studied using severalbioassays. Field rates of ten pesticides wereselective to the parasitoid pupae. Fresh residue(s)of cartap, chlorfenapyr, emamectin benzoate andpermethrin were highly toxic, causing 100% mortalityof adult females in every treatment. Residual effectsof these four insecticides on cabbage foliage showedthat only cartap was highly persistent. Cartapresidues caused 100% mortality for over 30 d. In thesame assay three chitin synthesis inhibitors(chlorfluazuron, flufenoxuron and teflubenzuron) andone fungicide/bactericide (copper nonylphenolsulfonate) and two bactericides (kasugamycin andoxolinic acid) were nontoxic to adults. Effects ofcontact toxicity of chitin synthesis inhibitors andfungicides/bactericides on the untreated progeny oftreated parents was also determined: there was nosignificant difference in parasitism rates betweenprogeny of treated and untreated adults. When thefield doses of these chemicals were fed orally,mortality of female parasitoids ranged from 0% to17.23%. However, oral ingestion adversely affectedthe parasitism rate (p < 0.05) in alltreatments except oxolinic acid. Selectivity oftested pesticides against D. semiclausum andintegration of compatible pesticides with thisparasitoid for IPM of cabbage are discussed.     

瓜实蝇2种蛹寄生蜂生防潜能比较

[目的] 比较研究蝇蛹俑小蜂与蝇蛹金小蜂对瓜实蝇的控制潜能。[方法] 采用非选择性实验测定蝇蛹俑小蜂与蝇蛹金小蜂对瓜实蝇蛹的寄生效能、繁殖能力,并研究覆土厚度对2种寄生蜂寄生效能的影响。[结果] 2种寄生蜂对瓜实蝇的寄生率无显著性差异,但蝇蛹金小蜂的平均单雌产后代数比蝇蛹俑小蜂的多,分别为30和23头。土壤厚度显著影响2种寄生蜂的寄生效能,随着土壤厚度的增加,2种寄生蜂对瓜实蝇蛹的寄生率均显著下降,但蝇蛹金小蜂的寄生率下降更为迅速;蝇蛹俑小蜂最深可寄生8 cm土壤下的瓜实蝇蛹,而蝇蛹金小蜂在土壤厚度达到3 cm时就不能完成寄生。[结论] 蝇蛹俑小蜂较蝇蛹金小蜂更适合应用于瓜实蝇蛹的生物防治。     

吡蚜酮对烟粉虱取食干扰效应的探讨

采用甘兰叶片浸液法测定了吡蚜酮对烟粉虱Bemisia tabaci(Gennadius)成虫、卵、1龄若虫和3龄若虫的致死作用。在所测试的浓度范围(9.38～300mg/L)内,烟粉虱若虫和成虫的校正死亡率均随吡蚜酮浓度的增大而顺次显著增大。取食75～150mg/L、9.38～37.5mg/L吡蚜酮处理叶片和清水处理叶片的存活成虫个体单头蜜露量(分别为0.37～0.42、0.59～0.72、1.48mm2)间存在显著差异(P<0.05)。用EPG技术研究了吡蚜酮对烟粉虱口针刺吸的不同阶段和取食活性的影响。接触低浓度吡蚜酮(75mg/L)时,最初粉虱能够正常开始取食,但不能从韧皮部正常吸取汁液。高浓度的吡蚜酮(300mg/L)抑制了口针向植物的插入。综合上述结果,说明吡蚜酮可望成为防治番茄黄曲叶病毒病载体-烟粉虱的重要药剂之一。     

Microbial control of cotton pests: use of the naturally occurring entomopathogenic fungus Aspergillus sp. (BC 639) in the management of Bemisia tabaci (Genn.) (Hemiptera: Aleyrodidae) and beneficial insects on transgenic cotton crops

The commercial adoption of transgenic Bacillus thuringiensis (Bt) cotton (Bollgard II®) reduced the use of insecticides to control Helicoverpa spp. However, the ineffectiveness of the Bt toxin against sucking pests such as silverleaf whiteflies (Bemisia tabaci) resulted in a marked increase in B. tabaci populations and in the use of insecticides to control this pest. The effect of the entomopathogenic fungus Aspergillus sp. BC 639 on B. tabaci and beneficial insects (predominantly predatory insects) was studied in commercial cotton field trials. The results showed that oil-based extracts of the entomopathogenic fungus BC 639 control the number of B. tabaci adults and nymphs in commercial transgenic cotton crops. The BC 639 fungus caused 60.0%, 67.2%, and 68.8% mortality in adults, and 54.6%, 62.3%, and 51.7% in nymphs at 7, 14, and 21 days after treatment, respectively, relative to the unsprayed controls. The effect of BC 639 at concentrations of 125, 250, and 500?ml/ha on low-density B. tabaci (～10 nymphs/leaf) did not differ significantly from that of the commercial insecticide (pyriproxifen). However, at higher densities (>50 nymphs per leaf), low concentrations of BC 639 (125 and 250?ml/ha) were not as effective as 500?ml/ha BC 639 in successfully controlling the pest. A simple graphic analysis suggested that the more B. tabaci nymphs per leaf, the fewer adults per leaf, and that once the number of nymphs increased to ～70 per leaf, a negative feedback regulatory effect reduced the survivorship of the nymphs and adults and/or caused the emigration of the adults from the contaminated leaves in search of new resources. Therefore, the ability of BC 639 to control B. tabaci adults and nymphs with minimal effects on predatory insects indicates its potential utility in supplementing integrated pest management programmes for cotton crops.     

The integrated use of chemical insecticides and the entomopathogenic nematode,Steinernema carpocapsae (Nematoda: Steinernematidae), for the control of sweetpotato whitefly,Bemisia tabaci (Hemiptera: Aleyrodidae)

The integration of chemical insecticides and infective juveniles of the entomopathogenic nematode Steinernema carpocapsae (Wesier) (Nematoda: Steinernematidae), to control second instars of the sweetpotato whitefly, Bemisia tabaci Gennadius (Hemiptera: Aleyrodidae) was investigated. Using a sand bioassay, the effects of direct exposure of S. carpocapsae for 24 h to field rate dilutions of four insecticides (spiromesifen, thiacloprid, imidacloprid and pymetrozine) on infectivity to Galleria mellonella larvae were tested. Although all chemicals tested, except spiromesifen, produced acceptable nematode infectivity rates, they were all significantly less than the water control. The effect of insecticide treatment (dry residues of spiromesifen, thiacloprid and pymetrozine and soil drench of imidacloprid) on the efficacy of the nematode against B. tabaci was also investigated. Nematodes in combination with thiacloprid and spiromesifen gave higher B. tabaci mortality (86.5% and 94.3% respectively) compared to using nematodes alone (75.2%) on tomato plants. There was no significant difference in B. tabaci mortality when using the chemicals imidacloprid, pymetrozine and spiromesifen in conjunction with nematodes compared to using the chemicals alone. However, using thiacloprid in combination with the nematodes produced significantly higher B. tabaci mortality than using the chemical alone. The integration of S. carpocapsae and these chemical agents into current integrated pest management programmes for the control of B. tabaci is discussed.