Evaluation of insecticides against aphids (Myzus persicae Sulzer) and caterpillars (spodoptera litura [f.]) on tobacco in Karnataka State (India)

0.02% a.i. dicrotophos and dimethoate, 0.025% a.i. demeton-S-methyl, thiometon, chlorfenvinphos and methomyl, and 0.03% a.i. phosphamidon were evaluated in the field for control of aphids (Myzus persicae Sulzer) infesting tobacco. All the insecticides were effective but chlorfenvinphos and methomyl were inferior to the rest. 0.03% and 0.06% a.i. endosulfan and trichlorfon, 0.05% and 0.1% a.i. carbaryl, and 0.025% and 0.05% a.i. methomyl were evaluated in the field for control of caterpillars ofSpodoptera litura (F.) defoliating tobacco. Nearly all the insecticides were effective and carbaryl and trichlorfon gave satisfactory control even at the lower concentrations tested.     

Effect of synthetic insecticides on the larvae of <Emphasis Type="Italic">Coccinella septempunctata</Emphasis> from Greek populations

Coccinella septempunctata L. is one of the most abundant ladybird species in Greece, preying on several aphid species and other arthropods, of which many are pests of cultivated plants. These pests are usually controlled with chemical insecticides. During this process, however, beneficials are also exposed to pesticides. The development of Integrated Pest Management (IPM) programs against aphids requires the evaluation of the effects of insecticides on beneficial insects. We evaluated the LD₅₀ of imidacloprid, acetamiprid, bifenthrin and deltamethrin on first, second, third and fourth instar larvae of C. septempunctata by topical application. Moreover, we studied their sublethal effects (LD₁₀) on the development, weight and prey consumption of fourth instar larvae. The topical application bioassays showed that deltamethrin and bifenthrin were highly toxic to all larval instars, whereas imidacloprid and acetamiprid were less toxic to fourth instar larvae. The LD₁₀ dose significantly affected, developmental time, adult weight and daily predation. These results show the importance of assessing potential effect of insecticides on C. septempunctata for developing effective IPM programs of aphids in Greece.     

Biochemical and physiological changes on Bacillus thuringiensis cotton after imidacloprid foliar spray

Bacillus thuringiensis cotton is a variety of cotton genetically modified to contain a gene derived from B. thuringiensis bacteria; which results in expression of toxin protein that confers resistance to bollworm complex (the most destructive pest of cotton). Introduction of Bt cotton lowered the need of insecticides, but still a number of insecticides are used for other insects like jassids, whitefly, aphids and tobacco caterpillar to which Bt gene does not provide effective control. Imidacloprid (tradename Imidacel 17.8 SL) is an insecticide designed for control of these major sucking/piercing insects that affect cotton. So in the present work we studied the post effect of imidacloprid insecticide on plant health of three Bt cotton hybrids (RCH-134, JKCH-1947, NCEH-6R) as there are reports of this insecticide causing growth and yield enhancements in absence of insect pests. Imidacloprid was first sprayed at recommended concentration (40 ml/acre) on 3 months old plants sown in randomly designed plots with three replications of each hybrid. The spray was repeated three times at 10 days interval. The level of B. thuringiensis gene expression, peroxidase activity and total phenols was measured on third day after every spray in leaves along with growth and yield of plants. The insecticide has shown to increase the level of B. thuringiensis protein, peroxidase enzyme activity, total phenols, height, number of bolls retained on plants and yield. These observations suggested that the imidacloprid treated plants showed better growth and development, thereby imidacloprid has growth enhancing effect on Bt cotton plants in addition to its insecticidal properties.     

Toxicity of butene-fipronil,in comparison with seven other insecticides,in <Emphasis Type="Italic">Leptinotarsa decemlineata</Emphasis> and <Emphasis Type="Italic">Drosophila melanogaster</Emphasis>

The speed of toxic action of an insecticide is an indicator for control efficacy and has considerable practical importance. For agricultural pest control, fast-acting is an important feature for an insecticide to consistently reduce the amount of feeding damage. Butene-fipronil is a novel compound obtained via the structural modification of fipronil. However, information about the toxicity and speed of toxic action is still limited. In the present paper, we compared the toxic feature of butene-fipronil with seven other insecticides, of which imidacloprid and abamectin are slow-acting insecticides, and acephate, endosulfan, methomyl, α-cypermethrin and spinosad are fast-acting insecticides. We found that the contact and stomach toxicities of butene-fipronil were among the highest ever estimated to Leptinotarsa decemlineata and Drosophila melanogaster. The speed of toxic action of butene-fipronil was determined using median lethal time (LT₅₀) at a dose (concentration) equivalent to LD₈₀ values. For L. decemlineata, the values for butene-fipronil, imidacloprid, abamectin, acephate, endosulfan, methomyl, cypermethrin and spinosad were calculated to be 39.9, 36.5, 37.5, 20.2, 22.4, 23.8, 16.4 and 23.1 h, respectively. Those for D. melanogaster were 29.8, 31.5, 29.4, 14.0, 20.3, 18.1, 13.5, and 20.1 h, respectively. ANOVA analysis showed that butene-fipronil, imidacloprid, abamectin had similar LT₅₀ values, whereas acephate, endosulfan, methomyl, spinosad and cypermethrin had comparable LT₅₀ values. Thus, butene-fipronil belongs to slow-acting insecticides. Our results provide more empirical information for butene-fipronil potential application.     

灭多威和吡虫啉对棉苗缩合单宁含量的影响

为明确常用杀虫剂对棉花抗虫性的影响,研究了灭多威和吡虫啉营养液处理对棉苗中抗虫次生物质缩合单宁含量的影响。结果表明,25mg/L灭多威处理3叶期棉苗后第6、9、12和15天,50mg/L灭多威处理棉苗后第6天和第15天,棉叶中缩合单宁含量均显著增加,其中25mg/L灭多威处理棉苗15天,棉叶中缩合单宁的含量较对照增加74%。50mg/L吡虫啉处理棉苗后第2天,棉叶中缩合单宁含量与对照相比增加了45%,而吡虫啉的其它处理浓度和处理时间未对棉苗缩合单宁含量产生显著影响。杀虫剂对棉苗缩合单宁含量的影响与杀虫剂本身的性质密切相关,其中灭多威对棉苗缩合单宁含量影响较大,而吡虫啉影响则较小。此外,杀虫剂对棉苗缩合单宁含量的影响还具有一定的剂量效应与时间效应。     

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.     

Side effects of insecticides used in wheat crop on eggs and pupae of <Emphasis Type="Italic">Chrysoperla externa</Emphasis> and <Emphasis Type="Italic">Eriopis connexa</Emphasis>

In Brazil, chemical control is one of the main tools to manage insect pests in wheat. However, this kind of management can impair the biological control provided by the predators Chrysoperla externa and Eriopis connexa. The present study evaluated the side effects on C. externa and E. connexa of 15 insecticides registered for wheat. Insecticides were sprayed on eggs and pupae via Potter tower at the maximum recommended dose. We evaluated the viability of eggs and pupae as well as the sub-lethal effects on fecundity and fertility of the adults emerged from treated pupae. The insecticides were classified according to the scale of toxicity proposed by IOBC. Regarding the eggs, the insecticide etofenprox was classified as slightly harmful (class 2) to C. externa. Imidacloprid + beta-cyfluthrin, diflubenzuron WG, thiamethoxam + lambda-cyhalothrin A and B, gamma-cyhalothrin, and etofenprox were also classified as slightly harmful (class 2) to E. connexa, while methomyl was classified as moderately harmful (class 3) for the eggs of the predator. The insecticide imidacloprid + beta-cyfluthrin was considered slightly harmful (class 2) to pupae of C. externa, while imidacloprid + beta-cyfluthrin, thiamethoxam + lambda-cyhalothrin A and B, and lufenuron were classified as slightly harmful (class 2) to the pupae of E. connexa. The insecticides beta-cyfluthrin, diflubenzuron SC, lambda-cyhalothrin, permethrin, thiamethoxam, triflumuron, and zeta-cypermethrin were harmless to eggs and pupae of both predators and should therefore be prioritized in the control of insect pests in wheat, thus preserving the natural biological control provided by C. externa and E. connexa.     

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.     

Biological characterization of sulfoxaflor, a novel insecticide

BACKGROUND: The commercialization of new insecticides is important for ensuring that multiple effective product choices are available. In particular, new insecticides that exhibit high potency and lack insecticidal cross‐resistance are particularly useful in insecticide resistance management (IRM) programs. Sulfoxaflor possesses these characteristics and is the first compound under development from the novel sulfoxamine class of insecticides. RESULTS: In the laboratory, sulfoxaflor demonstrated high levels of insecticidal potency against a broad range of sap‐feeding insect species. The potency of sulfoxaflor was comparable with that of commercial products, including neonicotinoids, for the control of a wide range of aphids, whiteflies (Homoptera) and true bugs (Heteroptera). Sulfoxaflor performed equally well in the laboratory against both insecticide‐susceptible and insecticide‐resistant populations of sweetpotato whitefly, Bemisia tabaci Gennadius, and brown planthopper, Nilaparvata lugens (Stål), including populations resistant to the neonicotinoid insecticide imidacloprid. These laboratory efficacy trends were confirmed in field trials from multiple geographies and crops, and in populations of insects with histories of repeated exposure to insecticides. In particular, a sulfoxaflor use rate of 25 g ha^?1 against cotton aphid (Aphis gossypii Glover) outperformed acetamiprid (25 g ha^?1) and dicrotophos (560 g ha^?1). Sulfoxaflor (50 g ha^?1) provided a control of sweetpotato whitefly equivalent to that of acetamiprid (75 g ha^?1) and imidacloprid (50 g ha^?1) and better than that of thiamethoxam (50 g ha^?1). CONCLUSION: The novel chemistry of sulfoxaflor, its unique biological spectrum of activity and its lack of cross‐resistance highlight the potential of sulfoxaflor as an important new tool for the control of sap‐feeding insect pests. Copyright © 2010 Society of Chemical Industry     

柑橘木虱防控药剂筛选及矿物油对其增效作用评价

为了筛选柑橘木虱高效防控药剂,提高药剂防治效果,本文探索了 10种杀虫剂对柑橘木虱的田间防效及矿物油对杀虫剂的增效作用.结果表明:对柑橘木虱成虫,22％噻虫·高氯氟悬乳剂(SE)、70％吡虫啉可湿性粉剂(WP)、6％联菊·啶虫脒微乳剂(ME)和5％高效氯氟氰菊酯ME的速效性好,药后1 d防效94.61％～100％;22...     

Behaviour modifying effects of low systemic concentrations of imidacloprid on Myzus persicae with special reference to an antifeeding response

With a combination of biological, analytical, electrophysiological, and video-optical methods, it was possible to show that low concentrations of the new chloronicotinyl insecticide, imidacloprid, strongly affect the behaviour of Myzus persicae (Sulz.), leading eventually to the death of the aphids. Tests to elucidate the biological properties were performed under laboratory conditions with cabbage leaf petioles placed in insecticidal solutions over different periods of time. LC_15(24h) values were considered as low concentrations and calculated for imidacloprid and pirimicarb, respectively. Imidacloprid at low concentrations depressed the honeydew excretion of apterous adults of M. persicae by almost 95% within 24 h without affecting the vitality of the majority of aphids, whereas, at equitoxic concentrations, pirimicarb showed much weaker effects on honeydew excretion, which strongly coincided with mortality. In choice experiments with alate morphs of M. persicae over 48 h, their larvae almost always occurred on the untreated control leaf, and were not found on the leaf which was treated systemically with low concentrations of imidacloprid. Apterous aphids placed on cabbage leaves systemically treated with low concentrations of imidacloprid showed nearly the same decrease in weight as untreated starving aphids, suggesting that their death was caused by starvation. Aphids that were moved from imidacloprid-treated to untreated leaves after 24 h began feeding on the latter and showed a steady increase in weight and honeydew production. This suggests that the behavioural response is reversible. Aphids on pirimicarb-treated (equitoxic dose) leaves showed no decrease in weight. Electrical penetration graphs revealed that M. persicae on artificial membranes containing imidacloprid probed more often before feeding than aphids on control sachets. Time-lapse videofilming of apterous adults placed on cabbage leaves revealed a migration from the leaf treated with low concentrations of imidacloprid to an untreated leaf. From the results of these experiments and the observed symptomatology it is possible to postulate two different and dose-dependent modes of action of imidacloprid on M. persicae: (1) the well-known mode of action with visually obvious irreversible symptoms (paralysis, tremor, uncoordinated leg-movement) at field rates, and (2) the reversible starvation response as an antifeedant effect, which is not coupled with typical symptoms of neuronal disorder, at lower concentrations.     

Potency of some novel insecticides at various environmental temperatures on<Emphasis Type="Italic">Myzus persicae</Emphasis>

An attempt was made to achieve low environmental risk control of insect pests using sublethal concentrations of insecticides, enhanced by the effect of high temperatures (>25°C). For each of the insecticides imidacloprid, abamectin, pirimicarb and azadirachtin, the lethal and sublethal concentrations were determined for the green peach aphidMyzus persicae (Sulzer) (Homoptera: Aphididae) and its predator, the lady beetleHarmonia axyridis (Pallas). The lady beetle was more tolerant of all four insecticides, as well as of high temperatures below 40°C, compared with the prey. The joint action of sublethal concentrations of insecticides and high temperatures was investigated to determine the sublethal concentrations and temperatures that would be effective in controlling the aphids, but not detrimental to the beneficial lady beetle. The results suggested a synergistic effect of sublethal insecticide concentrations and high temperatures against the green peach aphid.     

Responses of the cabbage seedpod weevil,Ceutorhynchus obstrictus (Marsham) (Coleoptera: Curculionidae), to seed treatments of canola (Brassica napus L.) with the neonicotinoid compounds clothianidin and imidacloprid

BACKGROUND: The cabbage seedpod weevil, Ceutorhynchus obstrictus (Marsham), is a major pest in the production of canola (Brassica napus L.) in North America and Europe, and effective population control is often essential for economical crop production. In North America, neonicotinoid insecticides have been used for several years in canola as seed treatments for reducing herbivory by flea beetles. The neonicotinoids clothianidin and imidacloprid were investigated to determine their effects on preimaginal development and on emergence of new‐generation adults of C. obstrictus in comparison with effects of lindane, a chlorinated hydrocarbon seed treatment. RESULTS: Mean numbers of second‐ and third‐instar larvae were significantly higher in plants seed‐treated with lindane than in plants treated with the neonicotinoid compounds, even though weevil oviposition was similar for all treatments. Emergence of new‐generation adults was reduced by 52 and 39% for plants seed‐treated with clothianidin and imidacloprid, respectively, compared with emergence from plants treated with lindane. CONCLUSION: Seed treatment with both clothianidin and imidacloprid produced systemic insecticidal effects on larvae of C. obstrictus, with clothianidin slightly more effective than imidacloprid. Use of clothianidin or imidacloprid as seed treatments can comprise an important component in the integrated management of cabbage seedpod weevil in canola. Copyright © 2009 Society of Chemical Industry     

Impact of two synthetic pyrethroids and methomyl on management of the cabbage aphid,brevicoryne brassicae (L.) and its associated parasitoid,diaeretiella rapae (M'Intosh)

The effectiveness of two synthetic pyrethroids, cypermethrin and fenvalerate, and of methomyl applied to cabbage plants was tested against the cabbage aphid, Brevicoryne brassicae (L.), and its parasitoid, Diaeretiella rapae (M'Intosh). Dosage rates chosen were equivalent to the manufacturer's maximum and minimum recommendations. Methomyl was considerably more toxic to B. brassicae adults than the two synthetic pyrethroids used. Fenvalerate, at the lowest rate used (71 g ha^?1), showed satisfactory effectiveness in reducing aphid adult population on treated plants by c. 77% below that of the control. All insecticides and rates used significantly reduced the emergence of parasitoid adult D. rapae from mummified aphids compared to the control. Fenvalerate clearly had less impact on emergence than cypermethrin or methomyl at any dosage used, while methomyl has appeared to be the most toxic compound in this respect. Longevity of parasitoid adults was highly affected by insecticide application, particularly those adults emerging from mummified aphids exposed to methomyl or cypermethrin. However, only a slight difference in longevity was seen at the lower rate of 71 g ha^?1 of fenvalerate. At the lowest dosage rates used, methomyl and cypermethrin reduced the F₁-progeny of adult parasitoid females by 70.5% and 58.3%, respectively, of the control, whereas fenvalerate reduced the progeny by only 36.4%.     

Toxicity and neurophysiological effects of selected insecticides on the mole cricket, Scapteriscus vicinus (Orthoptera: Gryllotalpidae)

Mole crickets (Scapteriscus spp.) are severe subterranean pests of turfgrasses, commonly targeted with neurotoxic insecticides. Ideally insecticides used against mole crickets should induce quick knockdown or mortality to minimize damage caused by their tunneling. However, neurophysiological effects of insecticides on mole crickets are mostly unknown. The aims of this study were to investigate neurophysiological and toxic effects of several insecticides on tawny mole cricket (Scapteriscus vicinus Scudder) adults and nymphs, and potential synergy between pyrethroid and neonicotinoid insecticides. Bifenthrin, fipronil, and the combination of bifenthrin + imidacloprid provided the fastest median mortality when injected. The combination of bifenthrin + imidacloprid elicited faster toxicity than either active ingredient alone. Imidacloprid, bifenthrin, and bifenthrin + imidacloprid caused immediate knockdown, whereas fipronil immobilized mole crickets within 1-2 h. Acephate, bifenthrin, fipronil, imidacloprid, and bifenthrin + imidacloprid caused significant neuroexcitation. Bifenthrin + imidacloprid resulted in greater increases of spontaneous neural activity than the additive effects of imidacloprid and bifenthrin alone. Excitatory compounds acting at sodium and chloride channels (bifenthrin and fipronil) were the most toxic against S. vicinus. Combining a sodium channel toxin (bifenthrin) and a synaptic toxin (imidacloprid) led to greater than additive neurophysiological and toxic effects, which to our knowledge provides the first documented evidence of synergistic neurological “potentiation”.     

Thiamethoxam is a neonicotinoid precursor converted to clothianidin in insects and plants

Neonicotinoid insecticides are compounds acting agonistically on insect nicotinic acetylcholine receptors (nAChR). They are especially active on hemipteran pest species such as aphids, whiteflies, and planthoppers, but also commercialized to control many coleopteran and some lepidopteran pest species. The most prominent member of this class of insecticides is imidacloprid. All neonicotinoid insecticides bind with high affinity (I₅₀-values around 1 nM) to [³H]imidacloprid binding sites on insect nAChRs. One notable ommission is the neonicotinoid thiamethoxam, showing binding affinities up to 10,000-fold less potent than the others, using housefly head membrane preparations. Electrophysiological whole cell voltage clamp studies using neurons isolated from Heliothis virescens ventral nerve cord showed no response to thiamethoxam when applied at concentrations of 0.3 mM, although the symptomology of poisoning in orally and topically treated noctuid larvae suggested strong neurotoxicity. Other neonicotinoids, such as clothianidin, exhibited high activity as agonists on isolated neurons at concentrations as low as 30 nM. There was no obvious correlation between biological efficacy of thiamethoxam against aphids and lepidopterans and receptor affinity in electrophysiological and binding assays. Pharmacokinetic studies using an LC-MS/MS approach to analyze haemolymph samples taken from lepidopteran larvae revealed that thiamethoxam orally applied to 5th instar Spodoptera frugiperda larvae was rapidly metabolized to clothianidin, an open-chain neonicotinoid. Clothianidin shows high affinity to nAChRs in both binding assays and whole cell voltage clamp studies. When applied to cotton plants, thiamethoxam was also quickly metabolized, with clothianidin being the predominant neonicotinoid in planta briefly after application, as indicated by LC-MS/MS analyses. Interestingly, the N-desmethylated derivative of thiamethoxam, N-desmethyl thiamethoxam, was not significantly produced in either lepidopteran larvae or in cotton plants, although it was often mentioned as a possible metabolite, being nearly as active as imidacloprid. In conclusion, our investigations show that thiamethoxam is likely to be a neonicotinoid precursor for clothianidin.     

吡虫啉及其复配剂不同施药方法对油菜蚜虫控制效果

2006-2009年,采用拌种和播种沟施药的方法,于河南郑州研究了新烟碱类杀虫剂吡虫啉及吡虫啉.辛硫磷复配剂对油菜蚜虫的全程控制效果。小区试验结果表明,用吡虫啉有效成分5g/kg种子拌种仅能有效控制苗期油菜蚜虫的危害,防治效果为90.79%～100%,对中后期油菜蚜虫控制效果不明显;用吡虫啉600g/hm2及吡虫啉.辛硫磷复配剂1320g/hm2采用播种沟施药对油菜蚜虫的防治效果分别为91.82%～94.49%和90.68%～95.34%;试验示范验证防治效果在92%以上,持效期长达7个月以上,可以达到一次用药控制油菜整个生长期蚜虫为害的效果,减少了用药次数,此方法简单易行、保护环境、保护天敌,是一种简化高效的具有推广价值的油菜蚜虫可持续控制技术。     

Using bioassays with the green peach aphid (Myzus persicae) to determine residual activity of two systemically soil-applied neonicotinoid insecticides in field-grown tobacco

Duration of systemic pesticide activity under field conditions has wide implications for pest management. Our aim was to determine the duration of activity of systemic insecticides commonly used in cultivated tobacco (Nicotiana tabacum) by measuring the levels of insect infestations on field plots and effects on reproduction and survival of the green peach aphid (Myzus persicae) in controlled bioassays using field grown leaves. Plants were treated with different concentrations of two systemic neonicotinoid pesticides, imidacloprid and thiamethoxam, and grown in small field plots. Our results show that these materials are effective under field conditions against aphids for at least 13 weeks after transplant. Pesticides also affected aphid reproduction and nymph survival in bioassays, although some aphids survived on pesticide-treated leaves. We also observed that leaf age affected aphid survival. We showed that neonicotinoids were very effective against M. persicae, aphids are a useful organism to assess pesticide efficacy early in the growing season, but plant characteristics are more important than pesticide concentration in the second half of the growing season.     

八种杀虫剂对黑粪蚊的防治效果及残留分析

选择8种杀虫剂,分别在实验室和菇房条件下研究其对黑粪蚊的防治效果和对平菇菌丝生长的影响,并分析施药后不同时间平菇中的农药残留.结果表明,40%辛硫磷EC、40%氧乐果EC、48%毒死蜱EC对黑粪蚊具有很好的防治效果,但对平菇菌丝的抑制率明显高于其它药剂;10%吡虫啉WP、4.5%高效氯氰菊酯EC不仅对黑粪蚊成、幼虫具有良好的防治效果,而且使用后对平菇菌丝生长的影响较小;2.5%高效氯氟氰菊酯EW、4.5%高效氯氰菊酯EC、1.8%阿维菌素EC等使用5天后均未检测到农药残留,5%氟虫腈SC和10%吡虫啉WP药后15天仍能检测到残留.     

Influence of pesticides and application methods on pest and predatory arthropods associated with cotton

Incidence of sucking pests was studied in a transgenic (Bt) and non-transgenic cotton (non-Bt) agro ecosystem in 2008 and 2009. Simultaneously, the influence of different pesticides applied in two different methods on sucking pests and generalist predators was investigated on transgenic cotton. In stem application, the insecticides solutions prepared were painted directly on the middle portion of the plant stem but in foliar application the recommended dosages of the insecticides were sprayed on the cotton plant. The transgenic and non-transgenic cotton did not differ significantly in the population of sucking pests. The different pesticides when applied by foliar sprays reduced significantly more sucking pests than stem application. Among the different insecticides used, imidacloprid caused the maximum reduction of the leaf hopper population, acetamiprid caused the maximum whitefly reduction, and clothianidin caused the maximum thrips reduction under foliar application. Via stem application, acetamiprid and thiomethoxam were found better in suppression of the sucking pests?? population, but the population of predators was significantly less disrupted by the stem application method. The foliar application was in general more effective; stem application may be more applicable early in the season when its efficacy was higher and when foliar sprays were particularly destructive to beneficial pests. In foliar application, all the systemic neonicotinoids like imidacloprid, clothianidin, admire, thiamethoxam and acetamiprid were found highly toxic to natural enemies in comparison with spirotetramat, buprofezin and fipronil.