The influence of hosts, temperature and food sources on the longevity of Trichogramma platneri

Feeding experiments were conducted with Trichogramma platneri Nagarkatti (Hymenoptera: Trichogrammatidae) reared from the Angoumois grain moth, Sitotroga cerealella (Oliver) (Lepidoptera: Gelechiidae). T. platneri provisioned with host eggs do not live any longer than T. platneri without host eggs. Longevity of T. platneri is inversely related to temperature declining from 53 days at 10 °C to 3 days at 35 °C for honey-fed parasitoids and from 9 days at 10 °C to 1 day at 35 °C for unfed parasitoids. Sugar sources are necessary to prolong longevity of T. platneri, but a source of amino acid did not promote longevity. Honey solutions greater than 10%, and 43% fructose and sucrose solutions increased longevity 10–13 fold to 15–20 days in comparison to water when fed daily to T. platneri. Parasitoids fed only at the onset of the trial had greater longevity than unfed parasitoids but had a shorter longevity than parasitoids fed daily, due to the evaporation of the sugar solutions and consumption of the honey. Aphid honeydew is a suitable field-available sugar source supporting longevity up to 10 days, but is not as good as other sugar sources. Stabilizing additives did not reduce evaporation of a dilute sugar solution nor prolong longevity of T. platneri. Simulating a daily dew fall by misting vials, to redissolve the crystallized food residues left after providing food at the onset of the trial, failed to increase parasitoid longevity.     

Comparative Analysis of the Reproductive Attributes of Three Commercially-Produced Trichogramma Species (Hymenoptera: Trichogrammatidae)

The reproductive attributes of commercially-produced Trichogramma platneri, T. minutum and T. pretiosum reared from eggs of both Ephestia kuehniella and Sitotroga cerealella were monitored at 25 C. The age-specific fecundity, longevity and progeny sex ratio and adult size were determined for individual females from all six combinations of Trichogramma and rearing host, using E. kuehniella as the experimental host. Rearing host had a significant influence on the lifetime fecundity, 3-day fecundity and longevity of all three Trichogramma species. In general, the performance of T. minutum and T. pretiosum was better when reared from S. cerealella, but that of T. platneri was superior when reared from E. kuehniella. The lifetime fecundity of the Trichogramma species was linearly related to longevity and the ranking between species was T. pretiosum > T. minutum > T. platneri. The age-specific pattern of oviposition for T. platneri was distinctly precocious, with 40% of its lifetime fecundity oviposited on the first day, in contrast to 17-24% for the other two species. Progeny sex ratio over the lifetime of the Trichogramma females was slightly male biased and differed significantly from 0.5 for T. minutum and T. platneri. Daily sex ratio for parasitoids reared from the most productive rearing host was female biased only for the first day of oviposition for T. platneri in contrast to the first 5-6 days of oviposition for the other two species. There was little evidence that any of the reproductive attributes of these Trichogramma species, reared from small host eggs, was dependent on the size of the adult females.     

Parasitism of obliquebanded leafroller (Lepidoptera: Tortricidae) in commercially managed Michigan apple orchards

The obliquebanded leafroller, Choristoneura rosaceana (Harris), is one of the major arthropod pests of apple in the United States. In 1999 and 2000, a survey of the obliquebanded leafroller parasitoid complex in commercially managed apple orchards in Michigan's two largest fruit production regions was conducted to determine the species present and their importance to obliquebanded leafroller population management. In total, 8,961 obliquebanded leafroller larvae were collected of which 2,174 were parasitized. Parasitism increased from the overwintering generation to the summer generation for both regions and both years. In 1999, 11% of the 1,126 overwintering obliquebanded leafrollers collected were parasitized, whereas 28% of the 3,669 summer generation were parasitized. In 2000, 8% of the 489 overwintering obliquebanded leafrollers collected were parasitized, whereas 26% of the 3,677 summer generation obliquebanded leafrollers collected were parasitized. In total, 20 species of hymenopteran and dipteran parasitoids from seven families were recovered from obliquebanded leafroller larvae over the course of the study. The most abundant hymenopteran parasitoids were Bassus dimidiator Nees (Braconidae) comprising 48% of the total parasitoids, followed by Colpoclypeus florus (Walker) (Eulophidae) (8% of the total) and Macrocentrus linearis (Nees) (Braconidae) (2% of the total). Dipteran parasitoids (Tachinidae) accounted for 36% of the parasitism and were largely comprised of Nilea erecta (Coquillett) (5%) and Actia interrupta Curran (13%). These collections represent new host records for B. dimidiator, Bassus annulipes (Cresson) Hyphantrophaga blanda (Osten Sacken), and Compsilura concinnata (Meigen). The parasitoid C. florus is also reported from Michigan for the first time.     

Compatibility of endoparasitoid Hyposoter didymator (Hymenoptera: Ichneumonidae) protected stages with five selected insecticides

Hyposoter didymator (Thunberg) (Hymenoptera: Ichneumonidae) is a koinobiont endoparasitoid that emerges from the parasitization of economically important noctuid pests. H. didymator also is considered one of the most important native biocontrol agents of noctuids in Spain. Side effects of five insecticides with very different modes of action (fipronil, imidacloprid, natural pyrethrins + piperonyl butoxide, pymetrozine, and triflumuron) at the maximum field recommended rate in Spain were evaluated on H. didymator parasitizing Spodoptera littoralis (Boisduval) larvae and pupae of the endoparasitoid. Parasitized larvae were topically treated or ingested treated artificial diet. Parasitoid cocoons were topically treated. Host mortality when parasitized larvae were treated, as well as further development of the parasitoid surviving (e.g., percentage of cocoons spun, adult emergence, hosts attacked, and numbered progeny) were determined. Toxicity after treatment of parasitized larvae differed depending on the mode of exposure and insecticide. Fipronil was always highly toxic; imidacloprid killed all host insects by ingestion, but it was less toxic to both host and parasitoids, when administered topically; natural pyrethrins + piperonyl butoxide and triflumuron showed differing degrees of toxicity, and pymetrozine was harmless. Parasitoid cocoons provided effective protection against all the insecticides, except fipronil.     

Toxicity of pesticides to <Emphasis Type="Italic">Tamarixia radiata</Emphasis>, a parasitoid of the Asian citrus psyllid

Sixteen pesticides including two fungicides were evaluated for toxicity to adult Tamarixia radiata (Waterston) (Hymenoptera: Eulophidae), a parasitoid of the Asian citrus psyllid, Diaphorina citri Kuwayama (Hemiptera: Psyllidae). Percentage mortality data were evaluated to generally assess IPM-compatibility of the pesticides with adult parasitoids. The following were found to be least compatible with (most toxic to) adult T. radiata based on the toxicity of direct sprays and potential long residual life on leaves: carbaryl, chlorpyrifos, and fenpropathrin. Although highly toxic to the parasitoid as direct sprays or freshly dried residues, each of the following was more compatible with T. radiata because the toxicity of residues of these pesticides was either low at one to three days after application or relatively non-persistent: abamectin, chenopodium oil, fenpyroximate, and spirotetramat. Depending on environmental conditions, imidacloprid (foliar-applied), phosmet, pyridaben, sulfur and 435 spray oil might also be somewhat more compatible for the same reasons. The pesticides that consistently appeared to be most compatible with T. radiata were aluminum tris, copper hydroxide, diflubenzuron, and kaolin clay (Surround WP).     

A space-efficient contact toxicity bioassay for minute Hymenoptera, used to test the effects of novel and conventional insecticides on the egg parasitoids Anaphes iole and Trichogramma pretiosum

We developed and tested anovel bioassay method for assessment of contactresidues of pesticides to minute Hymenoptera. This method maintained a plant-toxin-insectinterface representative of natural conditionsin the field or greenhouse, and wasspace-efficient. The procedure was useful instudies with both foliar residues and systemicuptake. Furthermore, the method was relativelystraightforward, easy to setup, andinexpensive. Tests with the egg parasitoidsAnaphes iole Girault (Hymenoptera:Mymaridae) and Trichogramma pretiosumRiley (Hymenoptera: Trichogrammatidae)confirmed that this method provided consistent,repeatable assessment of concentration-responserelationships for several insecticide classes. Other researchers studying pesticide effects onminute Hymenoptera might find this bioassaymethod helpful, especially in situations wherespace is limited. We discovered differentialsusceptibility of these parasitoids tospinosad, thiamethoxam, and oxamyl. The orderof toxicity for A. iole wasspinosad>thiamethoxam>oxamyl, and for T. pretiosum wasthiamethoxam>spinosad>oxamyl. Our resultsunderscored the danger of generalizingpesticide effects across even closely relatedinsects, and demonstrated that novel`selective' insecticides are highly toxic toA. iole and T. pretiosum.     

Defensive behaviour and biological activities of the abdominal secretion in the ant Crematogaster scutellaris (Hymenoptera: Myrmicinae)

Using bioassays, the defensive behaviour of Crematogaster scutellaris and the biological activities of its abdominal secretion were investigated. Beside classical aggressive behaviours such as grips, C. scutellaris workers performed frequent characteristic gaster flexions during interspecific encounters, sometimes tempting to apply their abdominal secretion topically on the enemy. The toxicity of the venom of C. scutellaris to other ants greatly differed among the species tested, some being killed after the topical application of only three droplets, while others were quite resistant to a dose of 90 droplets. All ant species tested were strongly and immediately repelled by a contact between their antennae or mouthparts with the venom of C. scutellaris. Abdominal secretion was never used during intraspecific interference and workers were resistant to a topical application of the venom of their own species. Intraspecific repellency was significant but moderate compared to interspecific one. Workers of C. scutellaris were never seen using their venom during prey capture. In conclusion, the main biological activity of the abdominal secretion of C. scutellaris seems to be its repellency to other ant species. This is supported by field experiments showing that Pheidole pallidula foragers were efficiently repelled at coexploited baits, allowing the monopolization of most prey by C. scutellaris.     

Effect of selected insecticides on the natural enemies Coleomegilla maculata and Hippodamia convergens (Coleoptera: Coccinellidae), Geocoris punctipes (Hemiptera: Lygaeidae), and Bracon mellitor, Cardiochiles nigriceps, and Cotesia marginiventris (Hymenoptera: Braconidae) in cotton

We evaluated the toxicity of three insecticides (lambda cyhalothrin, spinosad, and S-1812) to the natural enemies Bracon mellitor Say, Cardiochiles nigriceps Viereck, Coleomegilla maculata De Geer, Cotesia marginiventris (Cresson), Geocoris punctipes (Say), and Hippodamia convergens Guérin-Méneville, in topical, residual, and field assays. Lambda cyhalothrin exhibited the greatest toxicity to the natural enemies. In topical toxicity tests, lambda cyhalothrin adversely affected each natural enemy species studied. Residues of lambda cyhalothrin on cotton leaves were toxic to B. mellitor, C. nigriceps, C. maculata, and C. punctipes. Interestingly, residues of this insecticide were not very toxic to C. marginiventris and H. convergens. Geocoris punctipes and C. maculata numbers in the field generally were significantly lower for lambda cyhalothrin treatments than for the other four treatments, substantiating the previous tests. Although cotton aphids began to increase over all treatments around the middle of the test period, the number of cotton aphids in the lambda cyhalothrin plots was significantly higher than the number in any of the other treatments. As cotton aphids increased in lambda cyhalothrin field plots, the predator H. convergens also increased in number, indicating that lambda cyhalothrin did not adversely affect it in accordance with the residual tests. Spinosad exhibited marginal to excellent selectivity, but was highly toxic to each parasitoid species and G. punctipes in topical toxicity tests and to B. mellitor in residual tests. Spinosad generally did not affect the number of G. punctipes, H. convergens, and C. maculata in the field except for one day after the second application for G. punctipes. S-1812 exhibited good to excellent selectivity to the natural enemies. Some reduction of G. punctipes occurred for only a short period after the first and second application of this insecticide in the field. H. convergens and C. maculata were affected very little by S-1812.     

Topical and oral toxicity of sulfluramid, a delayed-action insecticide, against the German cockroach (Dictyoptera: Blattellidae)

The LD50 of sulfluramid topically applied to 2-d-old, fifth instars of the German cockroach, Blattella germanica (L.), was estimated at 14.5 micrograms/g (95% FL = 13.7-15.4 micrograms/g). Sulfluramid was significantly more toxic than topically applied hydramethylnon (LD50 = 29.2 [19.0-46.5] micrograms/g). Sulfluramid had delayed toxicity but caused mortality significantly faster than hydramethylnon after topical application. The oral LD50 against newly enclosed, fifth instars was estimated to be 4.1 (3.9-4.4) micrograms/g; this toxicity was significantly greater than when sulfluramid was topically applied. Mortality caused by sulfluramid occurred significantly more slowly in the dietary exposures than in the topical applications. Sulfluramid at 1,000 ppm in diets was not a feeding deterrent to nymphal B. germanica.     

拟除虫菊酯类杀虫剂对蜜蜂的毒性和影响

蜜蜂是最重要的农业授粉昆虫之一,蜜蜂在授粉过程中极有可能接触到广泛使用的广谱杀虫剂-拟除虫菊酯,大多数拟除虫菊酯对蜜蜂等农业授粉昆虫有较高的毒性.本文对拟除虫菊酯类杀虫剂的作用机理进行了综述;总结了蜂群及蜂产品中拟除虫菊酯类杀虫剂的残留现状、拟除虫菊酯对蜜蜂的急性毒性以及亚致死效应,讨论了拟除虫菊酯类杀虫剂复配农药对蜜...     

Side effects of insecticides on aphidius rhopalosiphi (Hym.: Aphidiidae) In laboratory

The toxicity of bifenthrin, cyfluthrin, λ-cyhalothrin, cypermethrin, deltamethrin, esfenvalerate, fluvalinate, phosalon and pirimicarb have been assessed in laboratory on the parasitic hymenoptera Aphidius rhopalosiphi. A strong toxic effect was found with every tested product when adult parasitoids were exposed to freshly applied residues on both glass plates and maize leaves for 24 hours. Only two products, fluvalinate and esfenvalerate, did not kill all the insects. No differences were observed between mortalities on glass plates and leaves. Applied on aphids mummies, cyfluthrin and deltamethrin slightly reduced the emergence of young parasitoids, but not their reproductive performance. The other tested products had no effects on adult emergence. On basis of these results, the insecticides are of comparable toxicity to A. rhopalosiphi in laboratory.     

Acute and sublethal effects of neonicotinoids and pymetrozine on an important egg parasitoid,Trichogramma ostriniae (Hymenoptera: Trichogrammatidae)

Both neonicotinoids and pymetrozine are important insecticides and may have the potential to be used in combination with natural enemies in integrated pest management (IPM). However, to determine their compatibility with biological control, it is necessary to examine the side effects of these chemicals on natural enemies. We examined the acute and sublethal effects of four commonly used neonicotinoid insecticides, imidacloprid, dinotefuran, nitenpyram and thiamethoxam, and the pyridine azomethine, pymetrozine, on adults of Trichogramma ostriniae. By analysing acute toxicity and evaluating the safety quotient of these chemicals, we found that thiamethoxam and dinotefuran pose extremely high risks to T. ostriniae, imidacloprid and nitenpyram posed high risks, but pymetrozine was found to have a low risk. In terms of sublethal effects, longevities of female wasps were significantly shortened when they were exposed to residues of dinotefuran. Percentages of ovipositing females decreased significantly after exposure to pymetrozine, thiamethoxam and dinotefuran. Numbers of offspring per female were significantly lower when females were exposed to pymetrozine, dinotefuran or thiamethoxam, compared with control females. Percentages of offspring that emerged as adults were lower when parental females were exposed to either pymetrozine or imidacloprid. Based on the results of the sublethal concentration assay and the acute toxicity bioassay, nitenpyram would be safe for IPM programmes utilising T. ostriniae, and we suggest that T. ostriniae could be released safely after foliar applications of nitenpyram. However, foliar application of imidacloprid, thiamethoxam, dinotefuran or pymetrozine in an agro-ecosystem where T. ostriniae is a predominant biocontrol agent should be carefully evaluated.     

Susceptibility of pest Nezara viridula (Heteroptera: Pentatomidae) and parasitoid Trichopoda pennipes (Diptera: Tachinidae) to selected insecticides

Susceptibility of the southern green stink bug, Nezara viridula (L.) (Heteroptera: Pentatomidae), and its endoparasitoid Trichopoda pennipes (F.) (Diptera: Tachinidae) to acetamiprid, cyfluthrin, dicrotophos, indoxacarb, oxamyl, and thiamethoxam was compared in residual and oral toxicity tests. In the residual toxicity test, cyfluthrin, dicrotophos, and oxamyl were highly toxic to N. viridula. Thiamethoxam was moderately toxic to these insects. Each of the four insecticides was highly toxic to T. pennipes after prolonged tarsal contact with dried residues of these chemicals. In the oral toxicity test, where N. viridula fed on food covered with insecticide residues, none of the insecticides were toxic to adults of this stink bug, but acetamiprid, dicrotophos, and thiamethoxam were moderately toxic to the nymphs. In the oral toxicity test, where N. viridula fed on a gel-food containing insecticides, cyfluthrin, dicrotophos, oxamyl, and thiamethoxam were highly toxic to this stink bug. In an oral toxicity test using contaminated sugar water, all of the insecticides were highly toxic to T. pennipes. Because insecticides were as toxic, or more toxic, to T. pennipes than to N. viridula, it is extremely important to conserve this parasitoid by applying these insecticides for control of southern green stink bugs only when the pest reaches economic threshold.     

Comparative selectivity of pesticides used in greenhouses,on the aphid parasitoid Aphidius colemani (Hymenoptera: Braconidae)

A series of bioassays were conducted under laboratory conditions to determine the relative toxicities of various pesticides (acetamiprid, cypermethrin, chlorantraniliprole and emamectin benzoate, Bacillus thuringiensis var. kurstaki and Helicoverpa armigera nucleopolyhedrovirus, copper oxychloride, iprodione, mandipropamid, a mixture of propamocarb?+?fluopicolide and mixture of fludioxonil?+?cyprodinil) on Aphidius colemani adults and mummies, as well as sublethal effects on female fecundity. Cypermethrin was highly toxic to pupa of A. colemani within host mummies. Acetamiprid, cypermethrin, emamectin benzoate, a mixture of propamocarb?+?fluopicolide and mixture of fludioxonil?+?cyprodinil were also highly toxic to A. colemani adults (92–100% mortality at 48?h post treatment). Mandipropamid, iprodione and copper oxycloride treatments significantly reduced fecundity of the female parasitoids. In contrast B. thuringiensis var. kurstaki, H. armigera nucleopolyhedrovirus and chlorantraniliprole were harmless (<30% mortality) to the parasitoid species tested according to International Organisation for Biological Control toxicity classification and are likely to be compatible with integrated pest management programmes.     

Juvenile and sublethal effects of selected pesticides on the leafminer parasitoids Hemiptarsenus varicornis and Diglyphus isaea (Hymenoptera: Eulophidae) from Australia

The pest leafminers Liriomyza huidobrensis (Blanchard), Liriomyza sativae (Blanchard), and Liriomyza trifolii (Burgess) (Diptera: Agromyzidae) have spread into South East Asia and Oceania, and they are likely to reach Australia in the near future. Two translaminar pesticides, cyromazine and abamectin, currently provide effective chemical control of these pests, but because parasitoids can play an important role in controlling and preventing leafminer outbreaks, understanding the impact of pesticides on leafminer parasitoids is vital. Here, we tested larval and pupal mortality and sublethal effects of abamectin, cyromazine, and the widely used fungicide mancozeb on two common Australian leafminer parasitoids, Hemiptarsenus varicornis (Girault) and Diglyphus isaea (Walker). Abamectin caused significant mortality to larvae and pupae of both parasitoid species but cyromazine and mancozeb did not. Progeny production and longevity of H. varicornis were not affected by adult exposure to cyromazine and mancozeb, nor did direct pupal exposure decrease number of progeny produced by either parasitoid. Mortality of H. varicornis females emerging from leaves treated with abamectin was high for up to 72 h after eclosion but those surviving beyond 72 h did not differ from control females in the number of progeny produced. Mancozeb did not influence leaf residence time or parasitism by H. varicornis females. Cyromazine and the fungicide mancozeb were concluded to be compatible with the parasitoids tested and suitable for integrated pest management of leafminers should outbreaks of pest species occur in Australia. Abamectin should be used with caution because it caused significant mortality in both parasitoids tested here.     

Toxicity of chemicals commonly used in Indonesian vegetable crops to Liriomyza huidobrensis populations and the Indonesian parasitoids Hemiptarsenus varicornis, Opius sp., and Gronotoma micromorpha, as well as the Australian parasitoids Hemiptarsenus varicornis and Diglyphus isaea

Liriomyza huidobrensis (Blanchard) and Liriomyza sativae (Blanchard) are important pests of vegetable crops in Indonesia and are likely to spread to neighboring countries. Three pesticides (dimehypo, abamectin, and cyromazine) are currently used to control these pests, but there is little information on their effectiveness against field populations and on their impact on parasitoids controlling Liriomyza species. The toxicity of these chemicals to L. huidobrensis and three common parasitoids (Hemiptarsenus varicornis Gerault, Opius sp., and Gronotoma micromorpha Perkins) was therefore evaluated in Indonesia with mortality laboratory assays. All three chemicals were effective against larvae of three populations of L. huidobrensis with different histories of chemical exposure. Dimehypo caused mortality in adult Opius sp., G. micromorpha, and H. varicornis, whereas abamectin was toxic only at concentrations substantially higher than the field rate. Cyromazine did not influence survival of the parasitoids. A commonly used fungicide, mancozeb, had no impact on parasitoid mortality. Trials were repeated with a strain of H. varicornis from Australia and a different parasitoid (Diglyphus isaea) recently found in Australia. Neither parasitoid was influenced by mancozeb or cyromazine. Abamectin applied at field rates caused some mortality among the adults of both species, but was less toxic than chlorpyrifos. Abamectin produced lower LC50s against Australian H. varicornis than against Indonesian H. varicornis. These results suggest that cyromazine can be incorporated into Liriomyza control programs in Indonesia that conserve parasitoids, whereas dimehypo and abamectin need to be used cautiously. Local Australian parasitoids should help control L. huidobrensis as long as only cyromazine and nontoxic fungicides are applied.     

Toxicity of three acaricides to Tetranychus urticae (Tetranychidae: Acari) and Orius insidiosus (Anthocoridae: Hemiptera)

Management for twospotted spider mite, Tetranychus urticae Koch, populations in peanut, Arachis hypogaea L., relies on acaricides. The outcomes of acaricide applications are most predictable when complete information on their toxicity and specificity is available. Specifically, the degrees to which acaricides impact different stages of T. urticae and natural enemies combined determine the overall efficacy of an acaricide application. The objectives of this study were to determine stage-specific direct and residual efficacies of three acaricides (fenpropathrin, etoxazole, and propargite) against T. urticae, and the direct and residual toxicity of the acaricides to Orius insidiosus (Say) adults. Direct toxicity of acaricides to T. urticae was measured on peanut cuttings. All acaricide treatments caused significant mortality to a mixed stage population of T. urticae, and mortality did not differ among the acaricides 7 d after treatment. When toxicity to eggs was tested, the proportion of eggs that hatched for all acaricide treatments was significantly lower than the control, with etoxazole and propargite causing 100% mortality. Exposure to acaricide residues caused < 30% mortality of T. urticae adults 1 and 2 d after treatment and was not significantly different from the control. Fenpropathrin and propargite caused 100% mortality and etoxazole caused > 50% mortality of O. insidious adults after direct exposure to the acaricides. Residual toxicity of acaricides to O. insidiosus adults varied but remained toxic to O. insidiosus longer than to T. urticae. Fenpropathrin had the longest residual effect on O. insidiosus adults, causing > 95% mortality after 14 d; etoxazole and propargite caused < 30% mortality after 14 d.     

Effects of pesticide applications on the euonymus scale (Homoptera: Diaspididae) and its parasitoid, Encarsia citrina (Hymenoptera: Aphelinidae)

Novel biorational insecticides are rapidly replacing more toxic, broad-spectrum compounds to control pests of ornamental plants. These new formulations are widely regarded as safe, effective, and environmentally sound with minimal impact on nontarget organisms. We tested several biorational and traditional insecticides for their ability to control euonymus scale, Unaspis euonymi (Comstock), and their potential impacts on the aphelinid parasitoid, Encarsia citrina (Crawford). Soil-applied acephate and foliar-applied pyriproxyfen exhibited superior control of euonymus scale, but also reduced numbers of surviving E. citrina. Imidacloprid failed to control euonymus scale and decreased parasitism by E. citrina. Thus, the potential impact of a pesticide on biological control is not necessarily predicted by its potential longevity, mode of delivery, or its toxicity to the target pest. Finding the best fit of a compound into an integrated pest management program requires a consideration of all these factors and direct study of effects on the natural enemies of pests.     

Fitness of Encarsia sophia (Hymenoptera: Aphelinidae) parasitizing Trialeurodes vaporariorum and Bemisia tabaci (Hemiptera: Aleyrodidae)

Abstract Fitness and efficacy of Encarsia sophia (Girault & Dodd) (Hymenoptera: Aphelinidae) as a biological control agent was compared on two species of whitefly (Hemiptera: Aleyrodidae) hosts, the relatively smaller sweetpotato whitefly, Bemisia tabaci (Gennadius) biotype ‘B’, and the larger greenhouse whitefly, Trialeurodes vaporariorum (Westwood). Significant differences were observed on green bean (Phaseolus vulgaris L.) in the laboratory at 27 ± 2°C, 55%± 5% RH, and a photoperiod of 14: 10 h (L: D). Adult parasitoids emerging from T. vaporariorum were larger than those emerging from B. tabaci, and almost all biological parameters of E. sophia parasitizing the larger host species were superior except for the developmental times of the parasitoids that were similar when parasitizing the two host species. Furthermore, parasitoids emerging from T. vaporariorum parasitized more of these hosts than did parasitoids emerging from B. tabaci. We conclude that E. sophia reared from larger hosts had better fitness than from smaller hosts. Those from either host also preferred the larger host for oviposition but were just as effective on smaller hosts. Therefore, larger hosts tended to produce better parasitoids than smaller hosts.     

Effects of bio-pesticides on Eretmocerus warrae (Hym., Aphelinidae), a parasitoid of Bemisia tabaci (Hom., Aleyrodidae)

The sweet potato whitefly Bemisia tabaci (WF) can be controlled by two commercial neem products, NeemAzal-T/S^® (1% azadirachtin) for foliar application, and NeemAzal-U (17% azadirachtin) for soil application, alongwith two biorational products of microbial origin, Abamectin (avermectin) and Success^® (spinosad). Side effects of these products were tested in a laboratory bioassay against a native aphelinid, Eretmocerus warrae (EW). Eggs and early larval instars of the parasitoid, commonly found outside the host body, were highly susceptible to foliar spray of neem with only 8%, 18% and 55% emergences of adults from treated eggs. larval and pupal stages respectively at recommended dose-rates of 5 ml/l and 1%, 8% and 40% at twice recommend dose-rate (10 ml/l). Soil application with NeemAzal-U marginally affected EW. At highest tested dose-rate of 3.0 g/l, 46%, 64% and 81% emergence was recorded after treatement of plants harbouring WF parasitized by egg, larval and pupal stages of EW respectively. In contrast to neem application, Success^® and Abamectin caused high mortality in development stages of the parasitoids. In particular, abamectin was highly toxic to the parasitoids with less than 1% emergence from either of the three development stages if treated with 1–2 ml/l.