The contact toxicity of indoxacarb and five other insecticides to Orius insidiosus (Hemiptera: Anthocoridae) and Aphidius colemani (Hymenoptera: Braconidae), beneficials used in the greenhouse industry

The contact toxicity of indoxacarb, abamectin, endosulfan, insecticide soap, S-kinoprene and dimethoate to Orius insidiosus (Say) and Aphidius colemani Viereck were studied in the laboratory. These beneficials are often used in the greenhouses to manage various insect pests. Indoxacarb is slow acting and therefore, to estimate lethal dosages, observations should be continued for several days until data stabilize. Seven days after treatment, the LC50 was 0.119 g AI litre(-1) for O insidiosus adults and 0.019 g AI litre(-1) for A colemani. At that time, the recommended field concentration was 0.479 times the LC50 for O insidiosus adults and three times the LC50 for A colemani. In contrast, indoxacarb had no adverse effect on the reproductive capacity of wasps surviving a treatment or the developing wasps in the aphid mummy. Among the other insecticides S-kinoprene was the most innocuous while dimethoate was the most toxic to the two beneficials. The other insecticides had overlapping toxicities.     

The effect of indoxacarb and five other insecticides on Phytoseiulus persimilis (Acari: Phytoseiidae), Amblyseius fallacis (Acari: Phytoseiidae) and nymphs of Orius insidiosus (Hemiptera: Anthocoridae)

A laboratory study assessed the contact toxicity of indoxacarb, abamectin, endosulfan, insecticidal soap, S-kinoprene and dimethoate to Amblyseius fallacis (Garman), Phytoseiulus persimilis Athias-Henriot and nymphs of Orius insidiosus (Say). Amblyseius fallacis is a predacious phytoseiid mite and an integral part of integrated pest management (IPM) programmes in North American apple orchards. The other two beneficials are widely used in greenhouses to manage various arthropod pests infesting vegetable and ornamental crops. Indoxacarb is a slow-acting insecticide, so toxicity data were recorded 7 days post-treatment when the data had stabilised. It showed no toxicity to O. insidiosus nymphs or to A. fallacis or P. persimilis adults. The LC50 values for O. insidiosus nymphs and P. persimilis could not be estimated with their associated confidence limits, because the g values were greater than 0.5 and under such circumstances the lethal concentration would lie outside the limits. The LC50 for A. fallacis was 7.6x the label rate. The fecundity of P. persimilis was reduced by 26.7%. The eclosion of treated eggs from both species of beneficial mites was not affected adversely. Among the other pest control products, S-kinoprene and endosulfan affected adversely at least one species of the predators, whereas dimethoate, abamectin and insecticidal soap were very toxic to all three beneficials. Indoxacarb should be evaluated as a pest control product in IPM programmes.     

Toxicity and sublethal effects of an insecticidal soap on Aphidius colemani (Hymenoptera: Braconidae)

BACKGROUND: The effects of an insecticidal soap on the survival, fitness and behaviour of an aphid parasitoid wasp, Aphidius colemani (Viereck), were studied in the laboratory. The LC(50) (soap concentration causing 50% mortality 24 h after treatment) was determined. The survival of parasitoid larvae (% adult emergence), fitness (tibia length of adults) and number of eggs produced per female parasitoid that survived in third- and fourth-instar aphids treated with insecticidal soap LC(50) were also assessed. The LC(50) for third- and fourth-instar aphids was determined to be 3.25 g L(-1). Acceptance by female parasitoids of aphids that survived their LC(50) was also tested. RESULTS: The soap concentration causing 100% mortality in adult wasps 24 h after treatment was 17.5 g L(-1). The LC(50) was 2.75 g L(-1). Soap did not have any effect on the survival of parasitoid immatures or on the fitness or number of eggs produced per female parasitoid. Wasps that were in contact with treated aphids did not oviposit as much in them as in untreated aphids, indicating that female parasitoids detected aphids treated with insecticidal soap. CONCLUSION: These data suggest that aphid parasitoids released following treatment with insecticidal soap are likely to accept a lower proportion of the surviving aphids. Biological control programmes could be ameliorated by soap applications if the latter were made 1 day before the release of wasps in the greenhouse.     

松毛虫赤眼蜂对三种农田常用杀虫剂的敏感性

为明确常用杀虫剂对松毛虫赤眼蜂Trichogramma dendrolimi的安全性,室内评估了高效氯氰菊酯、阿维菌素和氯虫苯甲酰胺3种药剂对其成蜂的急性毒力以及田间推荐使用剂量对赤眼蜂各发育阶段的间接影响,并模拟自然情况,测定了不同残留期的3种药剂对赤眼蜂存活和寄生能力的影响.结果表明:以LC₅₀进行评估,对松毛虫赤眼蜂毒力最高的为阿维菌素,其次是高效氯氰菊酯,氯虫苯甲酰胺毒力最小;在田间推荐使用剂量下,阿维菌素、高效氯氰菊酯和氯虫苯甲酰胺的安全系数分别为0.017、0.066和69.175;在推荐使用剂量下,氯虫苯甲酰胺处理含有不同发育阶段赤眼蜂的米蛾Corcyra cephalonica卵后,平均羽化率最高为90.43%,其次是高效氯氰菊酯为56.46%,阿维菌素仅为9.84%;接触0~7 d残留期阿维菌素的玉米叶片24 h,松毛虫赤眼蜂全部死亡,无米蛾卵被寄生,但接触3~7 d残留期氯虫苯甲酰胺的玉米叶片,赤眼蜂的死亡率和寄生米蛾卵数量与清水对照无明显差异.表明在实施释放赤眼蜂的害虫综合治理方案中,应尽量避免使用阿维菌素,而氯虫苯甲酰胺对赤眼蜂风险性极低,具有很好的相容性,可以推广使用.     

6种农药对瓜蚜的毒力测定及田间药效

为了筛选防治西瓜瓜蚜的有效药剂,用6种药剂进行了室内毒力测定和田间药效试验。结果表明,1.8%阿维菌素EC对瓜蚜的毒力最高,60g/L乙基多杀菌素SC毒力最低,48hLC50分别为0.38mg/L和2 225.63mg/L。6种药剂毒力大小依次为阿维菌素溴氰虫酰胺氟啶虫胺腈啶虫脒吡虫啉乙基多杀菌素。田间试验结果表明,1.8%阿维菌素EC 3 000倍、10%溴氰虫酰胺OD 2 000倍、22%氟啶虫胺腈SC 4 000倍对瓜蚜速效性及持效性均较好,3~14d防效均达到90%以上,防效差异不显著;20%啶虫脒WP 3 000倍和10%吡虫啉WP 3 000倍速效性及持效性均较差,1d防效分别为31.31%和6.66%,14d防效分别为57.39%和47.80%;60g/L乙基多杀菌素SC 1 000倍防效最差,药后14d的最高防效仅为34.70%。推荐田间轮换使用阿维菌素、溴氰虫酰胺、氟啶虫胺腈防治瓜蚜。     

Toxicity of insecticides to the sweetpotato whitefly (Hemiptera: Aleyrodidae) and its natural enemies

Efficient chemical control is achieved when insecticides are active against insect pests and safe to natural enemies. In this study, the toxicity of 17 insecticides to the sweetpotato whitefly, Bemisia tabaci (Gennadius), and the selectivity of seven insecticides to natural enemies of this insect pest were evaluated. To determine the insecticide toxicity, B. tabaci adults were exposed to abamectin, acephate, acetamiprid, cartap, imidacloprid, malathion, methamidophos, bifenthrin, cypermethrin, deltamethrin, esfenvalerate, fenitrothion, fenpropathrin, fenthion, phenthoate, permethrin and trichlorphon at 50 and 100% of the field rate (FR), and to water (untreated control). To determine the insecticide selectivity, adults of Encarsia sp., Acanthinus sp., Discodon sp. and Lasiochilus sp. were exposed to abamectin, acephate, acetamiprid, cartap, imidacloprid, malathion and methamidophos at 50 and 100% FR, and to water. Groups of each insect species were exposed to kale leaves preimmersed in each treatment under laboratory conditions. Mortality of exposed individuals was recorded 24 h after treatment. Cartap and imidacloprid at 50 and 100% FR and abamectin and acetamiprid at 100% FR showed insecticidal activity to B. tabaci adults. Abamectin at 50 and 100% FR was the least insecticidal compound to the natural enemies Acanthinus sp., Discodon sp. and Lasiochilus sp. The present results suggest that abamectin at 100% FR may decrease B. tabaci field populations but can still be harmless to predators. Implications of these results within an integrated pest management context are discussed.     

柴油及其与阿维菌素复配对柑橘全爪螨卵的作用

室内测定了柴油对柑橘全爪螨卵的毒力及其与阿维菌素复配植物油基新型乳油的杀卵作用。结果表明,柴油对柑橘全爪螨卵的LC50为2790.39μg/mL;两种柴油与阿维菌素复配新型乳油1000、750和500倍液3种浓度下的杀卵率均高于90%,其中添加了印楝油的复配剂3浓度的杀卵率与对照药剂24%螺虫乙酯SC 3000倍液相当。     

The efficacy of spinosad against the western flower thrips, Frankliniella occidentalis, and its impact on associated biological control agents on greenhouse cucumbers in southern Ontario

Insecticides are the most commonly used tactic to control western flower thrips (WFT), Frankliniella occidentalis Pergande (Thysanoptera: Thripidae), on greenhouse cucumber. However, WFT has developed resistance to several of the insecticides presently in use. In addition, some of these insecticides adversely affect greenhouse biological control agents used to control WFT, resulting in subsequent pest resurgence. Therefore, there is a need to identify novel insecticides with unique modes of action for use in integrated pest management (IPM) programs to effectively control WFT with minimal impact on associated biological control agents. In laboratory bioassays conducted in 2001, immature and adult WFT and three associated greenhouse biological control agents: Amblyseius cucumeris Oudemans (Acarina: Phytoseiidae), Orius insidiosus Say (Hemiptera: Anthocoridae) and Encarsia formosa Gahan (Hymenoptera: Aphelinidae) were exposed to direct, direct/residual, and residual contact applications of the novel biopesticide, spinosad (Conserve 120 SC), and the industry standard for whitefly control, endosulfan (Thiodan 50 WP). In all three types of assay, spinosad was effective against immature and adult WFT life stages. It showed low toxicity to A. cucumeris, moderate toxicity to O. insidiosus and high toxicity to E formosa. Greenhouse studies involving exposure of immature and adult WFT and adult biological control agents to cucumber leaves sprayed previously with spinosad supported the laboratory data. Spinosad showed low toxicity to A. cucumeris exposed to leaves 1 day after treatment (DAT), moderate toxicity to O. insidiosus 1 and 8 DAT, and high toxicity to E. formosa up to 28 DAT. These data, along with spinosad's unique mode of action, suggest it would be a valuable reduced-risk control agent for greenhouse cucumber IPM programs.     

Toxicity of biorational insecticides: activity against the green peach aphid, Myzus persicae (Sulzer)

The relationship between dose for each of four biorational insecticides (pyrethrins, neem extract, capsiacin extract, insecticidal soap) and mortality of the green peach aphid (Myzus persicae) was determined using a laboratory bioassay. These insecticides were toxic to aphids and paired mixtures of the insecticides provided synergistic activity as measured by aphid mortality under the laboratory bioassay conditions. Capsiacin extracts were found to provide low levels of mortality alone but acted synergistically in mixtures with the other insecticides and provided higher than expected levels of mortality. Activity as determined in the laboratory for each insecticide was not evident under field-use conditions in five separate experiments. Under field conditions and using common application methods, these insecticides did not provide significant levels of control of aphids.     

Toxicity of emamectin benzoate to Cydia pomonella (L.) and Cydia molesta (Busck) (Lepidoptera: Tortricidae): laboratory and field tests

BACKGROUND: Emamectin benzoate is a novel macrocyclic lactone insecticide derived from naturally occurring avermectin molecules isolated by fermentation from the soil microorganism Streptomyces avermitilis Kim & Goodfellow. The present study aims to evaluate the toxicity of emamectin benzoate to codling moth, Cydia pomonella (L.), and oriental fruit moth, C. molesta (Busck), under laboratory and semi‐field conditions. RESULTS: Dose response bioassays showed that emamectin benzoate had a high level of intrinsic toxicity to early‐stage larvae of both species, and that contact activity might contribute significantly to mortality. In the semi‐field trials, residual toxicity lasted for more than 1 week. Ovicidal activity was recorded only for C. pomonella (approximately 30%), irrespective of the concentrations tested. Field trials confirmed the efficacy of emamectin benzoate on codling moth when applied at 7 day intervals. Fruit damage, both from the first and second generations, was comparable with that on treatment with chlorpyrifos‐ethyl, used as a chemical reference. CONCLUSION: Emamectin benzoate may be considered a valuable tool for the control of codling moth as a component of an IPM programme. Its collective advantages are: high efficacy, lack of cross‐resistance with currently used products, control of secondary pests such as oriental fruit moth and selective toxicity that spares beneficials. Copyright © 2008 Society of Chemical Industry     

Toxicity of a formulation of the insecticide indoxacarb to the tarnished plant bug, Lygus lineolaris (Hemiptera: Miridae), and the big-eyed bug, Geocoris punctipes (Hemiptera: Lygaeidae)

Indoxacarb is a new oxadiazine insecticide that has shown outstanding field insecticidal activity. The toxicity of a 145 g litre-1 indoxacarb SC formulation (Steward) was studied on the tarnished plant bug Lygus lineolaris and the big-eyed bug Geocoris punctipes. Both insect species responded very similarly to indoxacarb in topical, tarsal contact and plant feeding toxicity studies. The topical LD50 of the formulation was c 35 ng AI per insect for both species. Prolonged tarsal contact with dry indoxacarb residues did not result in mortality for either insect species. However, both species were susceptible to feeding through dried residues of indoxacarb after spraying on young cotton plants. Feeding on water-washed plants resulted in lower mortality than that observed with unwashed plants, and toxicity declined even more dramatically after a, detergent rinse, indicating that much of the indoxacarb probably resides on the cotton leaf surface or in the waxy cuticle. These results were corroborated by HPLC-mass spectrometry measurements of indoxacarb residues on the plants. Greater mortality for both species was observed in a higher relative humidity environment. Higher levels of accumulated indoxacarb and its active metabolite were detected in dead G punctipes than in L lineolaris after feeding on sprayed, unwashed plants. When female G punctipes ate indoxacarb-treated Heliothis zea eggs, there was significant toxicity. However, only c 15% of the females consumed indoxacarb-treated eggs, and the rest of the females showed a significant diminution of feeding in response to the insecticide. Cotton field studies have shown that indoxacarb treatments at labelled rates lead to a dramatic decline in L lineolaris, with negligible declines in beneficial populations. A major route of intoxication of L lineolaris in indoxacarb-treated cotton fields thus appears to be via oral, and not cuticular, uptake of residues from treated cotton plants. The mechanisms for selectivity/safety for G punctipes are currently under investigation and may be a combination of differential feeding behavior and diminution of feeding by females exposed to indoxacarb-treated eggs.     

Response of two lacewing species to biorational and broad-spectrum insecticides

Green lacewings, includingChrysoperla rufilabris (Burmeister) andCeraeochrysa cubana (Hagen), are predators of small, soft-bodied insects including whiteflies. The silverleaf whitefly,Bemisia argentifolii Bellows & Perring [formerlyB. tabaci (Gennadius) strain B], is an important pest of agronomic, vegetable and ornamental crops. Practical use of these lacewings as biological control agents would be facilitated by better understanding of their responses to both biorational (selective) and broad-spectrum insecticides. The topical and residual toxicity of azadirachtin (Azatin-EC^TM), insecticidal soap (M-Pede^TM), paraffinic oil (Sunspray Ultra-Fine Spray Oil^TM) and the pyrethroid bifenthrin (Brigade^TM) to eggs, larvae and adults of the lacewings were studied in the laboratory. Larvae ofC. cubana were much more tolerant to residues of bifenthrin than wasC. rufilabris and were somewhat more tolerant to topically applied soap. At normal field concentrations, azadirachtin (0.005%, by wt a.i.), paraffinic oil (1.0% by volume) and soap (1.0% by volume) were not toxic to larvae or adults of either species either topically or residually. Oil was toxic topically to eggs but azadirachtin and soap were not. Bifenthrin was toxic topically and residually to larvae and adults but was not so toxic to eggs as was oil. Thus, selectivity of all materials tested was relative to lacewing species and lifestage. The relative tolerance to insecticide residues exhibited byC. cubana larvae may be related to its trash-carrying habit, suggesting that use of trash-carrying chrysopids in place of non-trash carriers for augmentative biological control would increase options for non-disruptive chemical intervention when necessary.     

含酰肼结构阿维菌素衍生物的合成及生物活性

为减少能源消耗和环境污染,提高阿维菌素B2的实际应用价值,将阿维菌素B2a的23-OH氧化成羰基后分别与吡啶甲酰肼、苯磺酰肼、溴代苯甲酰肼以及肼基甲酸甲酯等反应,设计合成了6个新的酰肼类阿维菌素B2a衍生物,采用高分辨质谱(HRMS)、核磁共振氢谱(1H NMR)等对新化合物的结构进行表征,并初步测试了其对小菜蛾、蚜虫...     

四种杀虫剂对桃蚜和异色瓢虫的选择毒性及 害虫生物防治与化学防治的协调性评价

测定了吡虫啉、鱼藤酮、阿维菌素和印楝素4种杀虫剂对桃蚜及其捕食性天敌异色瓢虫成虫的相对毒力。4种药剂对桃蚜的毒力大小依次为阿维菌素＞吡虫啉＞鱼藤酮＞印楝素,其LC50分别为0.042、1.96、6.54和10.17 mg/L。对异色瓢虫的LC50则分别为1009.42、201.89、8202.90和大于7500 mg/L,益害毒性比分别为24033.81、103.01、1254.27和大于786.63。4种药剂在有效防治桃蚜的前提下对天敌异色瓢虫的安全性依次为阿维菌素＞鱼藤酮＞印楝素＞吡虫啉。阿维菌素、吡虫啉、印楝素和鱼藤酮这4种药剂均可在蚜虫综合治理中发挥有效的作用。     

3种药剂对象耳豆根结线虫卵及2龄幼虫的影响

为了筛选对象耳豆根结线虫Meloidogyne enterolobii防治效果好的药剂,本文采用浸虫法分别测试了 3％阿维菌素微乳剂、41.70％氟吡菌酰胺悬浮剂及20％噻唑膦水乳剂不同浓度、不同处理时间对象耳豆根结线虫2龄幼虫的致死作用,以及对卵孵化和卵胚胎发育的影响.结果表明,3％阿维菌素微乳剂对2龄幼虫致死作用最...     

添加Silwet 408对3%阿维菌素微乳剂药液表面张力和接触角及其对两种害虫作用效果的影响

通过室内测定和田间防治试验,研究了在3%阿维菌素微乳剂中添加不同量的有机硅表面活性剂Silwet 408后,对药液的表面张力及在苹果叶片上接触角的影响,以及添加助剂后药剂对苹果红蜘蛛Panonychus ulmi和苹果绣线菊蚜Aphis citricola毒力及防效的变化。结果表明:Silwet 408能有效降低3%阿维菌素微乳剂药液的表面张力及其在苹果叶片上的接触角,且在试验添加量(质量分数)3%~10%范围内,表面张力和接触角均随助剂添加量的增加而不断降低。生物测定结果表明:添加Silwet 408可显著提高3%阿维菌素微乳剂对苹果红蜘蛛的毒力及田间防效,但对苹果绣线菊蚜的毒力和田间防效则无明显影响。研究表明,在杀虫剂中添加增效助剂以提高药效时,除了需考察该助剂能否显著降低药液的表面张力及在靶标上的接触角外,害虫种类也是需考虑的因素之一。     

Differential susceptibility to abamectin and two bioactive avermectin analogs in abamectin-resistant and -susceptible strains of Colorado potato beetle, Leptinotarsa decemlineata (Say) (Coleoptera: Chrysomelidae)

As resistance to currently used insecticides increases in the Colorado potato beetle (CPB), Leptinotarsa decemlineata (Say), abamectin and its 4″-epi and 8,9-oxide analogs may serve as likely replacements if proven effective. We previously selected an abamectin-resistant strain of CPB (AB-F) that is suitable for the determination of cross-resistance to these two bioactive avermectin analogs. Using bioassay and logit analysis, the present work shows that, on average and following normalization by weight, the larval stages of the insecticide-susceptible SS strain are equally sensitive to the toxic action of abamectin and its 4″-epi and 8,9-oxide analogs, indicating that all three compounds retain high bioactivity towards the susceptible larval stages. Abamectin and the two analogs also are similar in toxicity to the larval stages of the AB-F strain. However, the AB-F larval stages are significantly less sensitive on average to these insecticides than the SS larval stages, indicating resistance to abamectin and cross-resistance to both the two analogs tested. Likewise, adults of the AB-F strain are significantly less sensitive to the toxic action of abamectin and the two analogs compared to SS adults, also indicative of resistance and cross-resistance. Abamectin is significantly more toxic, however, to both SS and AB-F adults, respectively, than either of the two analogs. The reduction in sensitivity was particularly evident in SS adults to both the 4″-epi and 8,9-oxide analogs. Additionally, adults of the SS strain are significantly less sensitive to the toxic action of abamectin and the two analogs when compared to SS larval stages. There is no significant differences, however, in the toxicity of these three insecticides, respectively, between larval and adults stages of the AB-F strain. This phenomenon results in lower resistance ratio (RR) values calculated for the two avermectin analogs compared to those calculated for abamectin regardless of the insect stage examined but is particularly evident and significant in the adult stage. This relative decrease in resistance levels is primarily associated with SS adults that are less sensitive to the toxic action of these insecticides. The decrease in abamectin toxicity is apparently due to significantly increased levels of P450 associated with SS adults versus forth instars and to similar levels in adults of the SS and AB-F strains. Because abamectin resistance in CPB is due in large part to enhanced oxidative metabolism of abamectin, it is likely that the SS adults are more tolerant to abamectin due to an enhanced level of oxidative detoxification. Finally, neither abamectin nor the two analogs are structurally protected at the specific molecular locations, C₃″, C₂₄, and C₂₆ carbons, which leads to enhanced oxidative metabolism, resistance and cross-resistance. Structurally-protected avermectin analogs at these vulnerable intramolecular sites are likely to be more effective insecticides in suppressing the development of oxidative detoxification-based resistance to abamectin, as would the use of oxidative synergists.     

Activity of abamectin against larval stages of Spodoptera littoralis boisduval and Heliothis armigera hübner (Lepidoptera: Noctuidae) and possible mechanisms determining differential toxicity

Marked changes in the relative toxicity of topically-applied abamectin were found between larval instars of Spodoptera littoralis, toxicity decreasing up to the fifth instar but increasing over 500-fold (at LD₅₀ level) in the sixth instar. By contrast, the toxicity of abamectin remained constant from fifth to sixth instar Heliothis armigera and there was an increase in the toxicity of two chemically unrelated insecticides, malathion (4-fold) and lambda-cyhalothrin (2.5-fold), from fifth to sixth instar S. littoralis. Prior topical application or injection of the microsomal oxidase inhibitor, piperonyl butoxide (PB) increased the toxicity of abamectin (6–8 and 16-fold respectively) against fifth instar S. littoralis, while topically-applied PB increased the proportion of radioactivity present as abamectin in the ventral nerve cord of this instar following topical application with [³H]abamectin. Topically-applied PB also enhanced the toxicity of abamectin against third (4-fold) and fourth instar (5-fold) S. littoralis but had no significant effect on sixth instar S. littoralis, fifth instar H. armigera, or on the toxicity of malathion and lambda-cyhalothrin against fifth instar S. littoralis. Topical application of the esterase inhibitor, S,S,S-tributyl phosphorothioate (DEF) significantly increased the toxicity of abamectin at the LD₅₀ level (3-fold) against fifth instar S. littoralis. The toxicity of injected abamectin against fifth instar S. littoralis was greater (20-fold) than with topical application but injected abamectin was less toxic (2-fold) against sixth instar S. littoralis and had no significant effect on fifth instar H. armigera. It is suggested that differential toxicity of abamectin is due in part to greater metabolism and reduced penetration in fifth instar S. littoralis than in sixth instar S. littoralis or fifth instar H. armigera.     

Activity of neem (Azadirachta indica A. Juss) seed kernel extracts against the mustard aphid,Lipaphis erysimi

An aqueous, an ethanolic and a hexane extract obtained from neem(Azadirachta indica A. Juss) seed kernels were tested for insecticidal activity against the mustard aphid,Lipaphis erysimi Kalt. The hexane extract, which exhibited a much higher activity than the two other extracts, had an LC50 of 0.674%. When the hexane extract was partitioned with ethanol, the ethanol-soluble fraction had an LC₅₀ of 0.328%, whereas the ethanol-insoluble part showed no activity even at 1%. Column chromatography of the ethanol-soluble fraction yielded eight compounds: nimbin, epinimbin, desacetylnimbin, salannin, desacetyl-salannin, azadirachtin and two unidentified compounds — a salannin derivative and a nonterpenoid. Of these, only five could be tested. Nimbin and epinimbin exhibited no toxicity at 0.3%, whereas salannin, a salannin derivative and the non-terpenoid gave LC₅₀ values of 0.055, 0.096 and 0.104%, respectively.     

15种杀虫剂对草地贪夜蛾卵的毒力测定

采用浸卵法测定了15种杀虫剂对草地贪夜蛾卵的毒力,并比较了不同杀虫剂的毒力水平。结果表明:100 mg/L处理后48 h,甲氨基阿维菌素苯甲酸盐(甲维盐)和灭多威对草地贪夜蛾卵孵化抑制率最高,达到100%,其LC 50分别为12.67 mg/L和16.95 mg/L;而200 mg/L的氯虫苯甲酰胺、多杀霉素、阿维菌素、高效氯氰菊酯、虱螨脲、辛硫磷和杀螟丹分别处理后72 h对草地贪夜蛾卵的孵化抑制率次之,在69.6%~87.65%之间,其LC 50分别为44.1、50.9、78.37、79.0、98.15、126.8 mg/L和137.7 mg/L。依据毒力测定的结果和高效低毒类杀虫剂优先选用的原则,推荐选择甲维盐、氯虫苯甲酰胺、多杀霉素、阿维菌素和高效氯氰菊酯作为防治草地贪夜蛾卵的主要药剂。