Few indirect effects of baculovirus on parasitoids demonstrate high compatibility of biocontrol methods against Tuta absoluta

BACKGROUND

Combining different biocontrol agents, particularly micro- and macroorganisms, can contribute to new and sustainable pest control approaches. Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) is one of the most destructive pests of solanaceous crops. An emerging management strategy consists of biological control using microbial insecticides such as baculoviruses, but with limited efficacy. Thanks to their high target specificity, baculoviruses can be used simultaneously with natural enemies such as parasitoids for improved control of T. absoluta. However, potential indirect nontarget effects of baculoviruses on parasitoids can result from overlapping resource requirements. We assessed whether ovipositing parasitoid females discriminated against virus-treated hosts and examined the outcome of within-host competition between the hymenopteran parasitoids Necremnus tutae (Reuter) (Eulophidae) and Dolichogenidea gelechiidivoris Marsch (Braconidae), and the Phthorimaea operculella granulovirus (PhopGV, Baculoviridae) that infects T. absoluta larvae.

RESULTS

Female D. gelechiidivoris discriminated against virus-treated hosts, whereas N. tutae did not. We found few indirect virus-related effects depending on the species, the sex, and the time of virus treatment. Effects were ambivalent for D. gelechiidivoris offspring and ranged from increased male longevity when infection occurred before parasitization to reduced emergence and male longevity when infection occurred after parasitization. N. tutae offspring showed a longer development time and shorter male longevity when they developed in virus-treated hosts.

CONCLUSION

The virus had a low impact on parasitoid offspring. In rare cases, adverse effects were detected; however, the low magnitude of these effects is unlikely to reduce the fitness of parasitoid offspring, therefore both parasitoids seem compatible with the baculovirus for control of T. absoluta. © 2022 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.     

Side effects of pesticides on the larvae of the hoverfly <Emphasis Type="BoldItalic">Episyrphus balteatus</Emphasis> in the laboratory

The hoverfly Episyrphus balteatus (Degeer) is one of the most abundant predators of the cabbage aphid (Brevicoryne brassicae (L.)) in brussels sprouts in Belgium. In the current laboratory study, the toxicity of several insecticides applied at maximum recommended field rates was investigated on the larvae of E. balteatus. Two- to 3-day-old larvae were confined in glass petri dishes with dry residues of freshly applied insecticides. Their mortality was checked daily until adult emergence. Sub-lethal effects were investigated by assessing the reproductive performance of adult hoverflies, originating from the surviving larvae. Of the five compounds tested, only pirimicarb caused 100% larval mortality. The corrected mortality for spinosad was 60% and the adults obtained from the surviving larvae did not succeed in laying eggs. Therefore, pirimicarb and spinosad were rated “harmful” (International Organization for Biological and Integrated Control of Noxious Animals and Plants (IOBC) category 4) for the larvae of E. balteatus. In contrast, flonicamid, thiacloprid and spirotetramat yielded much lower mortality percentages. The hatching rate of hoverfly eggs treated with flonicamid was 25.6% vs 48.7% in the control. Hence, flonicamid was rated “slightly harmful” (IOBC category 2). The fertility of adults treated as larvae with thiacloprid or spirotetramat was not affected (IOBC category 1). These laboratory trials suggest that thiacloprid and spirotetramat can be used safely in integrated pest management programs to control the cabbage aphid. Pirimicarb, spinosad and flonicamid should be tested in semi-field and field situations to assess their toxicity under more realistic conditions.     

Effect of antifeedants on the diamondback moth (Plutella xylostella) and its parasitoid Cotesia plutellae

Two neem preparations and the bitter‐tasting synthetic chemical denatonium benzoate were tested in the laboratory as antifeedants against the diamondback moth, Plutella xylostella L. The effects of the three materials on Cotesia plutellae (Kurdjumov), a hymenopteran parasitoid of ­P xylostella, were also recorded. All three materials significantly reduced the food consumption of ­P xylostella larvae. Parasitoid cocoons were formed on approximately half of those larvae which had been exposed to female C plutellae, regardless of antifeedant treatment, but emergence of adult parasitoids from the cocoons was significantly reduced by antifeedant treatment. In terms of food consumption and mortality of unparasitised P xylostella larvae, and emergence of adult C plutellae, the effect of each antifeedant preparation was directly related to the concentration of material used, but the effects of the neem preparations were greater than those of denatonium benzoate. However, no adult P xylostella emerged on any antifeedant treatment, therefore some of the parasitoids survived antifeedant treatments which were fatal to the unparasitised hosts. © 2000 Society of Chemical Industry     

Evaluation of selective toxicity of five pesticides against Plutella xylostella (Lep: Plutellidae) and their side-effects against Cotesia plutellae (Hym: Braconidae) and Oomyzus sokolowskii (Hym: Eulophidae)

The toxicities of five pesticides commonly used in vegetable fields to the larvae of the diamondback moth, Plutella xylostella (L) and its two major parasitoids, Cotesia plutellae (Kurdjumov) and Oomyzus sokolowskii (Kurdjumov), were evaluated in the laboratory using several bioassays. When tested at the rates recommended for field application by the manufacturer, fipronil, avermectin and chlorfluazuron produced over 95% mortality on third-instar larvae of P xylostella, but fenvalerate and methomyl did not produce any substantial mortality to such larvae, and over 70% of P xylostella larvae could still pupate normally after feeding on cabbage leaf treated with the two pesticides. In a residual contact assay with adult parasitoids, fipronil and methomyl caused over 93% mortality within 24 h; fenvalerate killed approximately 55% of the adults within 24 h; avermectin and chlorfluazuron showed differential toxicity to the two parasitoids. Avermectin was extremely harmful to O sokolowskii but slightly toxic to C plutellae, while chlorfluazuron was more toxic to C plutellae than to O sokolowskii. In the residue assay with cocoons of C plutellae and pupae of O sokolowskii developed within P xylostella pupae, treatments with pesticides did not reduce adult emergence. However, the mortality of C plutellae adults emerged from the fipronil-treated cocoons increased greatly within 24 h post-emergence; adults from the fenvalerate-treated cocoons parasitized less host larvae. Treatments with fenvalerate and methomyl significantly increased the mortality of O sokolowskii adults within 24 h post-emergence. Recommendations of choosing pesticides for the control of P xylostella are given.     

Valuation of gamma irradiation for proficient production of parasitoids (Hymenoptera: Chalcididae & Eucoilidae) in the management of the peach fruit-fly,Bactrocera zonata (Saunders)

Recognizing the potential significance of using nuclear techniques in biological control, investigations were conducted on the rearing of parasitoids of the peach fruit-fly, Bactrocera zonata (Saunders) (Diptera: Tephritidae) to lead to a greater flexibility in the use of irradiated hosts. For improving mass production of the biological control agents, the use of irradiated fruit-fly larvae at the dose of 15 Gy proved useful for enhancing the parasitism and adult emergence of the larval parasitoid, Trybliographa daci (Weld) (Hymenoptera: Eucoilidae) due to no negative repercussions on parasitoid development. Overall, parasitism by the parasitoid increased with age of the host larvae; however, significantly higher parasitism occurred on 4 d-old irradiated larvae of B. zonata compared to those aged 5 d. The female parasitoids preferred the irradiated larvae, and significantly higher numbers of larvae were parasitized compared with non-irradiated larvae. There was no significant difference in adult parasitoid emergence with respect to the sex of the host. A radiation level of 80 Gy was the best dose for rearing of the pupal parasitoid, Dirhinus giffardii (Silvestri) (Hymenoptera: Chalcididae) owing to broad tolerances in the use of irradiation for the rearing of fruit-fly's parasitoids. Percentage parasitism by D. giffardii varied with host pupal age, and the preference of the female parasitoid was lower on 48 h old host pharate pupae due to optimum size and mass of host. Present findings further revealed that the 24 h old host pupae of B. zonata were relatively more suitable for the maximum parasitism and progeny production of D. giffardii. Parasitisms by D. giffardii and T. daci were significantly higher on B. zonata host when parasitoids were released at a density of 3000 individuals per acre (7500 per hectares) than the other release rates of parasitoids for the management of fruit-flies in mango orchards. The implementation of these findings ought to help improve the mass production of parasitoids and the effectiveness of releases of biocontrol agents for control of B. zonata in mango plantations.     

Toxicity of some insecticides to Apanteles plutellae a parasite of the diamond back moth∗

Abstract

The susceptibility of adults and cocooned stages of Apanteles plutellae Kurdj. (Hymenoptera, Braconidae) to four synthetic pyrethroid insecticides and five other chemical insecticides was tested. The chemicals, formulated as emulsifiable concentrates, were decamethrin (0.0014%), permethrin (0.01%), fenvalerate (0.01%), cypermethrin (0.005%), dichlorvos (0.05%), monocrotophos (0.05%), endosulfan (0.05%), phosalone (0.05%) and quinalphos (0.05%). Adults were exposed for 6 h to filter paper impregnated with insecticide solution and were then transferred to untreated vials for observation. Cocoons were sprayed with the chemicals by means of a glass atomiser and held for adult emergence. The pyrethroid formulations and phosalone had little or no harmful effect on the adults and cocooned stages of A. plutellae but quinalphos was highly toxic to all stages tested. Dichlorvos, monocrotophos and endosulfan were highly toxic to adults but relatively safe for the cocooned stages.     

Sublethal effects of insecticides on the diamondback moth Plutella xylostella (L.)

The effect of sublethal concentrations (LC₁ and LC₅₀) of permethrin, fenvalerate, methamidophos and carbaryl on diamondback moth development, female fecundity and insect behaviour was investigated. All the insecticides had deleterious effects on the number of larvae surviving to pupae, the duration of the pupal period, the number of pupae surviving to adulthood, and cocoon formation in pupae. Prolonged duration of the larval period, from third instar to pupation, and deformed pupae were also observed. Permethrin, fenvalerate and carbaryl caused latent toxicity and deformed wings in the adults. Pyrethroids and methamidophos reduced the longevity of the adults whereas carbaryl increased it. Except for permethrin, the insecticides inhibited female fecundity. At LC₁ and LC₅₀ concentrations, the pyrethroids showed both repellent and antifeedant activity against larvae, and female moths preferred to oviposit on untreated leaf discs rather than on those treated with the pyrethroids at concentrations equal to their LC₅₀ values.     

Toxicity of selected insecticides to the two-spot ladybird <Emphasis Type="Italic">Adalia bipunctata</Emphasis>

The toxicity of pirimicarb, imidacloprid, dimethoate, lambda-cyhalothrin, flonicamid and spinosad to the two-spot ladybird, Adalia bipunctata, was evaluated in a laboratory study. Susceptibility of fourth instars and female adults was assessed by measuring toxicity via residual contact and ingestion through feeding on contaminated green peach aphids (Myzus persicae). Flonicamid and spinosad had no lethal effects on larvae and female adults. Pirimicarb was harmless to the predator by ingestion exposure but showed some residual toxicity at high concentrations to both larval and adult stages. Imidacloprid was highly toxic to the larval stage by residual and ingestion exposure but caused very low adult mortality when ingested through contaminated prey. Dimethoate and lambda-cyhalothrin were highly toxic to both the larval and adult stages of the ladybird. Our findings indicate that pest management programs in agricultural crops using dimethoate, lambda-cyhalothrin and, to a lesser degree, imidacloprid, are detrimental to A. bipunctata, whereas pirimicarb, flonicamid and spinosad are more compatible with the use of this predator.     

Inoculation

Terpenes and biogenically related phenols commonly found in plant essential oils are known to be toxic to insect pests. Accordingly thymol was tested for acute toxicity via topical application to diamondback moth, Plutella xylostella L. (Lepidoptera: Plutellidae) and its parasitoid, Cotesia plutellae (Kurdjunov) (Hymenoptera: Braconidae under laboratory conditions. Topical application to adult female parasitoids versus second instars of P. xylostella showed that thymol was about 62 times less toxic to the parasitoid than to the host larvae with 24 h LD₅₀ of 0.052 and 0.0008M, respectively. Although thymol was less toxic to the parasitoid, some biological parameters of the progeny at sublethal doses of surviving parasitoids were impaired such as rate of emergence and development time of larvae and pupae. The impact on detoxification enzymes was also studied and there was no significant induction in cytochrome P450 and carboxylesterase activities in both treated male and female wasps. Results obtained suggest that parasitoid is able to withstand the impact of thymol significantly.     

多杀菌素对菜蛾绒茧蜂的致死和亚致死效应

以对多杀菌素高抗的小菜蛾纯合子品系作寄主饲养菜蛾绒茧蜂,用多杀菌素田间推荐使用浓度(25 mg/L)分别处理处于卵期、幼虫期和蛹期的绒茧蜂,其中卵期和幼虫期通过处理寄主幼虫间接处理,并测定该药剂对成虫的毒力,系统观察该杀虫剂对绒茧蜂各虫期的致死和亚致死作用。与对照相比,绒茧蜂卵期或幼虫期其寄主受药后,可导致蜂幼虫死于寄主体内或啮出寄主的过程中,使结茧化蛹率下降43% ~56%,成虫羽化率下降19% ~33%,成蜂雌性比下降11% ~25%,而成虫大小、寿命和寄生力未受显著影响;在蛹期受药使成虫羽化率下降10%,成蜂寿命缩短,但对成虫寄生力无显著影响;对成虫24 h的LC99为4.31 mg/L。结果表明,多杀菌素可进入寄主作用于其体内的蜂卵和幼虫,或直接作用于蜂蛹和成虫,从而对绒茧蜂各个虫态产生显著的致死和亚致死效应,尤以对成虫高毒。     

核型多角体病毒与中红侧沟茧蜂对寄主棉铃虫的联合效应

为明确寄生蜂中红侧沟茧蜂Microplitis mediator与核型多角体病毒（nucleopolyhedrovirus,NPV）对寄主棉铃虫Helicoverpa armigera的联合效应,测量中红侧沟茧蜂和NPV单处理及复合处理后棉铃虫幼虫的形态学指标,并统计棉铃虫幼虫死亡率及寄生蜂中红侧沟茧蜂子代存活率。结果显示,处理3 d和5 d后,中红侧沟茧蜂和NPV单处理及复合处理的棉铃虫幼虫体长、体宽、头壳宽度、体重均显著低于对照,但各处理之间差异不显著。接入浓度为2.5×10⁴ OBs/mL和2.5×10⁶ OBs/mL NPV时,中红侧沟茧蜂和NPV这2种生防因子对棉铃虫均表现为拮抗效应或累加效应。接入浓度为2.5×10⁴ OBs/mL NPV时,先寄生后接毒和先接毒后寄生处理的棉铃虫实际死亡率分别为4.35%和14.26%;接入浓度为2.5×10⁶ OBs/mL NPV时,棉铃虫实际死亡率则分别为31.55%和94.19%,先接毒后寄生处理的棉铃虫实际死亡率均显著高于先寄生后接毒处理的实际死亡率。接入浓度为2.5×10⁶ OBs/mL NPV时,先寄生后接毒和先接毒后寄生处理的寄生蜂子代存活率分别为54.51%和3.71%,前者显著高于后者。表明中红侧沟茧蜂寄生和NPV侵染均能显著抑制棉铃虫的生长发育,但两者联合应用时拮抗效应明显且对寄生蜂子代有影响,同时用于生物防治棉铃虫时应谨慎。     

硒对亚洲玉米螟生长发育和生殖行为的影响

为探讨硒(selenium)对亚洲玉米螟Ostrinia furnacalis(Guenée)的营养作用及其生长发育、生殖行为的影响,选用添加不同浓度硒的人工饲料饲喂3龄幼虫,观察了蛹、成虫的生长发育及成虫生殖行为情况。结果表明,不同浓度的硒对蛹和成虫的发育影响差异较大,其中硒浓度为0.75 mg/kg时生长发育最好,化蛹率、雄蛹体重和雄蛾寿命显著高于对照,分别提高了7.4%、12.7%和19.1%;硒浓度为5.00 mg/kg时生长发育最差,化蛹率和羽化率最低,雌、雄蛹重最小,成虫寿命最短。当硒浓度为0.75 mg/kg时,雌蛾求偶百分率和求偶持续时间均有所降低,且求偶高峰期推迟1~2 h。以正常雌蛾为诱源时,硒雄蛾的定向能力显著低于对照,而以硒雌蛾为诱源时,硒雄蛾的定向能力显著高于对照雄蛾;硒雌蛾的产卵量和卵孵化率显著提高,硒雌蛾×硒雄蛾组合提高最多,分别为28.9粒和9.3%。研究表明,适量硒可以促进亚洲玉米螟生长发育,并能显著影响成虫的生殖行为。     

Bt玉米对中红侧沟茧蜂发育的间接影响及室内行为研究

利用Y-型嗅觉仪研究了中红侧沟茧蜂(Microplitis Mediator Haliday)对Bt玉米、常规玉米、粘虫幼虫和其虫粪及虫害苗挥发物的行为反应,同时研究了Bt玉米对中红侧沟茧蜂发育的影响。结果表明,两种玉米健康植株的挥发物对中红侧沟茧蜂均有引诱作用;中红侧沟茧蜂对两种玉米的健康植株及机械损伤株挥发物之间的选择性无显著差异;相对于Bt玉米,中红侧沟茧蜂更趋向于选择常规玉米的虫伤苗及玉米-粘虫幼虫-虫粪混合物的挥发物。与对照(寄生于取食常规玉米粘虫的中红侧沟茧蜂)相比,寄生于取食Bt玉米粘虫幼虫的中红侧沟茧蜂幼虫历期延长,出茧率、茧重、羽化率、蜂重均有显著降低,茧历期、蜂历期则差异不显著。     

Routine On-farm Soil Tillage Helps Control Asparagus Fly (Plioreocepta Poeciloptera)

Asparagus fly (Plioreocepta poeciloptera (Schrank, 1776)) is a serious pest in German asparagus (Asparagus officinalis L.) production. To evaluate the effects of different routine on-farm soil tillage measures on the number of flies emerging the following spring, asparagus fields in Lower Saxony, Germany, were investigated. Soil samples were taken before and after tillage in autumn 2017 and autumn 2018. Investigations were also conducted in both years on the effect that the soil depth at which asparagus fly pupae were buried had on the emergence of adult flies.

This study revealed that the number of emerging flies was not reduced by mulching, but was significantly reduced by subsequent tillage and/or tillage and dam formation. The emergence rate of adult flies was significantly reduced the deeper the pupae had been buried the previous autumn. The effects also depended on the year. The highest mean emergence rate observed was 68% and 45% for pupae buried at a depth of 10?cm and 20?cm, respectively. In conclusion, the key mechanism causing a decrease in asparagus fly population the following spring through routine on-farm tillage could be the burial of pupae when forming dams. Routine on-farm soil tillage can be regarded as a physical measure for controlling asparagus fly and is therefore an essential tool in the integrated pest management of asparagus production.

     

棉蚜和棉长管蚜对3种杀虫剂的敏感性比较

本文采用浸叶生测法和田间活性试验测定了棉蚜和棉长管蚜对吡虫啉?氟啶虫酰胺?吡蚜酮的敏感性?结果显示:阿拉尔?阿瓦提?图木舒克三地棉蚜对吡虫啉的敏感性低于棉长管蚜, 棉蚜和棉长管蚜对氟啶虫酰胺和吡蚜酮的敏感性无明显差异?在田间试验中, 施用吡虫啉后三地棉长管蚜的虫口减退率均显著高于棉蚜, 施用氟啶虫酰胺和吡蚜酮1 d后三地棉长管蚜和棉蚜的虫口减退率存在显著差异, 3 d和7 d后均无显著性差异, 虫口减退率均分别达到80%以上和90%以上?研究结果可为防治棉花蚜虫合理施药提供参考?     

The side-effects of pesticides onDiaeretiella rapae, a parasitoid of the turnip aphid (Lipaphis erysimi)

Diaeretiella rapae (M’Intosh.) is an endoparasite of the turnip aphid,Lipaphis erysimi (Kalt.) with a wide geographical distribution. The four Pesticides Nogos 50 EC at 600 ml per acre, Dimecron 50 WSC, Monofos 40 WSC and Tamaron 600 SL at 500 ml per acre, used in practice for the control of this pest, were tested for their side-effects onD. rapae. The parasitoid was reared on pottedBrassica napus plants infested with aphid under laboratory conditions (22±2°C, 60–70% rel. hum., 16 h light and 8 h dark). In one test, adult female parasitoids were exposed to fresh pesticide residues on glass plates and in another test, the pupae within aphid mummies were directly sprayed. The results revealed that Dimecron 50 WSC, Nogos 50 EC and Monofos 40 WSC were harmful causing 100% mortalitv toD. rapae followed by Tamaron 600 SL (97% moderately harmful) after 24 hours of application, compared to no mortality in control, where only water was sprayed. Directly spraying of pupae with Dimecron 50 WSC and Nogos 50 EC reduced adult parasitoid emergence to 9 and 7%, respectively, Monofos 40 WSC and Tamaron 600 SL to 3% compared to 78% emergence for the control within one week of treatment. The results showed that none of the tested pesticides was safe toD. rapae and according to the International Organization for Biological Control (IOBC) further testing under semi-field and field conditions is recommended.     

Penetration and insecticidal activity of diflubenzuron in Tenebrio molitor pupae

Diflubenzuron was found to be effective on the pupae of Tenebrio molitor L. (Coleoptera, Tenebrionidae) when applied topically, by dipping, or by injection. Death occurred before or at adult ecdysis, or during the first few days after emergence. Its effectiveness decreases with increasing age of the pupa. Diflubenzuron delays adult ecdysis and decreases the longevity of normally ecdysed adults. After diflubenzuron had been applied topically or by dipping, the compound was determined, on the pupal cuticle, in the body and on the rearing tray, by highperformance liquid chromatography. The results showed that diflubenzuron penetrated rapidly into the body and was not degraded during the pupal life. The level of incorporation of the insecticide, in dipping experiments on pupae at the same stage, varied from one individual to another. Moreover, the mean amount of insecticide incorporated was lower after dipping of older pupae than of younger pupae. It is suggested that the lower efficacy of diflubenzuron on older pupae may be caused by the decrease both in the permeability of the cuticle and in the sensitivity of the target cells.     

氟啶虫胺腈等11种杀虫剂对瓜蚜的毒力及协同增效作用

为探寻防治瓜蚜的高效协同增效药剂组合,采用叶片带虫浸渍法测定了氟啶虫胺腈等11种杀虫剂对瓜蚜的毒力。结果表明:处理后24 h,氟啶虫胺腈对瓜蚜的毒力最高,吡蚜酮最低,LC₅₀值分别为10.15和369.63 mg/L;48 h时依然是氟啶虫胺腈毒力最高,而高效氯氟氰菊酯最低,LC₅₀值分别为2.35和117.57 mg/L。在此基础上进行协同增效药剂筛选,结果表明:按质量比计,氟啶虫酰胺与吡蚜酮1 : 1、氟吡呋喃酮与吡蚜酮1 : 5、氟啶虫胺腈与吡蚜酮1 : 3、氟吡呋喃酮与高效氯氟氰菊酯1 : 5、氟啶虫胺腈与高效氯氟氰菊酯1 : 5几种组合的增效作用显著,共毒系数分别达1 271、820、561、1 277和478。研究结果可为田间瓜蚜的高效化学防治提供科学依据。     

Bioresidual and integrated pest management status of a biorational agent and a novel insecticide against whitefly and its key parasitoids

The effects of continuous exposure of the adult and crawler stages of the whitefly, Trialeurodes vaporariorum, and adult of the parasitoids Encarsia formosa and Eretmocerus eremicus to spray deposits of potassium salts of a fatty acid and diafenthiuron applied at recommended rates were evaluated. French bean, Phaseolus vulgaris Prince, plants were sprayed and the adults confined on them using modified 5 cm Petri dishes. Fresh (4 - 5-h-old) deposits of fatty acids resulted in a 10.7% mortality rate of whitefly adults and 8.0 and 10.7% mortality rates of E. formosa and E. eremicus adults respectively, while fresh deposits of diafenthiuron resulted in a 62.7% mortality rate of whitefly adults and 12.0 and 14.7% mortality rates of E. formosa and E. eremicus respectively. The mortality rate (6.9 and 69.7%) of whitefly crawlers was recorded when exposed to 24-h-old deposits of fatty acids and diafenthiuron respectively. The mortality rate declined as the deposits aged. Adult parasitoid emergence from the treated pupae was unaffected. Spray deposits of diafenthiuron were effective against whitefly for up to 2-3 weeks in comparison with fatty acids, which were effective only when sprayed. Both products were harmless to adults as well as pupae of both parasitoids irrespective of the exposure period (age of deposits) tested (IOBC Class 1). These insecticides can be included in integrated pest management strategies against whitefly with the fatty acids used on horticultural crops.     

Effect of a neem seed kernel suspension onTelenomus remus,an egg parasite ofSpodoptera litura

Laboratory tests showed that a 2% neem (Azadirachta indica A. Juss) seed kernel suspension (NSKS) in water sprayed onSpodoptera litura (F.) eggs before or after parasitization did not adversely affect the emergence of the egg parasiteTelenomus remus Nixon. When sprayed on eggs before parasitization, the treatment did not repel the parasite. The treatment accelerated the development of the parasite but significantly reduced the longevity of its adult. When parasitized eggs were treated, NSKS significantly increased the adult parasite longevity. Thus, a schedule of NSKS sprays can be integrated withT. remus for the control of the tobacco caterpillar,S. litura, in tobacco nurseries.