Application timing and efficacy of alternatives for the insecticidal control of Tipula paludosa Meigen (Diptera: Tipulidae), a new invasive pest of turf in the northeastern United States

BACKGROUND: Two invasive crane flies, Tipula paludosa Meigen and Tipula oleracea L. (Diptera: Tipulidae), were detected in New York State for the first time in 2004. Both are damaging pests of turfgrass and other horticultural systems in North America where establishment has already been documented. To develop management recommendations for the Northeast and define opportunities for preventive (autumn) and curative (spring) control, four insecticide trials targeting T. paludosa larvae were conducted over a 2 year period.RESULTS: The most efficacious (>/=70% control in both trials) products against early instars in autumn were bifenthrin, carbaryl, chlorantraniliprole, clothianidin and trichlorfon. Results varied for azadirachtin, Beauveria bassiana, cyfluthrin, dinotefuran, imidacloprid, imidacloprid + bifenthrin and indoxacarb. Clothianidin and dinotefuran were most efficacious against fourth instars in spring; results varied for imidacloprid, indoxacarb and trichlorfon.CONCLUSION: Several insecticides offer alternatives for preventive and curative control of T. paludosa, but, because there is little overlap with application windows for scarab larvae pests, management may entail an entirely new insecticide treatment window, implying new economic and environmental burdens to the turfgrass industry. Moreover, curtailing the impact and spread of these invasives may be severely hampered because the best performing alternatives (clothianidin, dinotefuran) are not registered in New York. Copyright (c) 2008 Society of Chemical Industry.     

Toxicities and sublethal effects of seven neonicotinoid insecticides on survival, growth and reproduction of imidacloprid-resistant cotton aphid, Aphis gossypii

BACKGROUND: Imidacloprid has been a major neonicotinoid insecticide for controlling Aphis gossypii (Glover) (Homoptera: Aphididae) and other piercing–sucking pests. However, the resistance to imidacloprid has been recorded in many target insects. At the same time, cross‐resistance of imidacloprid and other insecticides, especially neonicotinoid insecticides, has been detected. RESULTS: Results showed that the level of cross‐resistance was different between imidacloprid and tested neonicotinoid insecticides (no cross‐resistance: dinotefuran, thiamethoxam and clothianidin; a 3.68–5.79‐fold cross‐resistance: acetamiprid, nitenpyram and thiacloprid). In the study of sublethal effects, imidacloprid at LC₂₀ doses could suppress weight gain and honeydew excretion, but showed no significant effects on longevity and fecundity of the imidacloprid‐resistant cotton aphid, A. gossypii. However, other neonicotinoid insecticides showed significant adverse effects on biological characteristics (body weight, honeydew excretion, longevity and fecundity) in the order of dinotefuran > thiamethoxam and clothianidin > nitenpyram > thiacloprid and acetamiprid. CONCLUSION: The results indicated that dinotefuran is the most effective insecticide for use against imidacloprid‐resistant A. gossypii. To avoid further resistance development, the use of nitenpyram, acetamiprid and thiacloprid should be avoided on imidacloprid‐resistant populations of A. gossypii. Copyright © 2011 Society of Chemical Industry     

七种新烟碱类杀虫剂对韭菜迟眼蕈蚊幼虫及蚯蚓的选择毒力

为筛选出高效安全的韭蛆防治药剂,室内采用胃毒触杀联合毒力法比较了吡虫啉、啶虫脒、噻虫嗪、噻虫胺、呋虫胺、烯啶虫胺、噻虫啉与毒死蜱和高效氯氟氰菊酯等6种对照药剂对韭菜迟眼蕈蚊幼虫的毒力,同时用人工土壤法测定了13种药剂对蚯蚓的急性毒性,并通过盆栽试验验证了其对韭蛆和蚯蚓的选择毒力。结果表明,吡虫啉、噻虫胺、呋虫胺、噻虫啉、噻虫嗪对韭菜迟眼蕈蚊4龄幼虫的毒力明显高于6种对照药剂,对虫酰肼的相对毒力倍数分别为101.6、55.0、32.9、27.2、13.6;13种供试药剂中,除吡虫啉、啶虫脒、噻虫胺、呋虫胺对蚯蚓中等毒性外,其余均为低毒;盆栽试验中,吡虫啉、噻虫嗪、毒死蜱、噻唑膦、高效氯氟氰菊酯的防虫效果和保苗效果均分别高于其它药剂,但其中只有噻虫嗪对蚯蚓没有明显致死作用。     

四种新烟碱类杀虫剂对蜜蜂的急性毒性及初级风险评估

采用饲喂管法和点滴法,分别测定了吡虫啉、噻虫嗪、噻虫胺、啶虫脒4种原药及其制剂对意大利蜜蜂成年工蜂的急性毒性,并采用危害商值(HQ)法进行了初级风险评价。结果表明:饲喂管法测得97.3%吡虫啉原药、25%吡虫啉可湿性粉剂、96%噻虫嗪原药、30%噻虫嗪悬浮剂、97%噻虫胺原药、5%噻虫胺可湿性粉剂、96%啶虫脒原药及40%啶虫脒可溶性粉剂的经口毒性48 hLD50值分别为有效成分8.04×10-3、9.46×10-3、7.04×10-3、4.64×10-3、11.8×10-3、5.25×10-3、5.22和6.31μg/蜂;点滴法测得各药剂的接触毒性48 h-LD50值分别为有效成分2.46×10-2、1.33×10-2、3.63×10-2、9.27×10-3、1.52×10-2、2.21×10-2、5.82和5.07μg/蜂。按《化学农药环境安全评价试验准则》的毒性等级划分标准,啶虫脒原药及其可溶性粉剂对蜜蜂的急性毒性均为中等毒,其他6种药剂对蜜蜂的急性毒性均为高毒;根据危害商值(HQ),啶虫脒对蜜蜂为低风险,吡虫啉、噻虫嗪和噻虫胺对蜜蜂均存在高风险。     

Comparative acute toxicity of neonicotinoid and pyrethroid insecticides to non‐target crayfish (Procambarus clarkii) associated with rice–crayfish crop rotations

BACKGROUND: Most insecticides used to control rice water weevil (Lissorhoptrus oryzophilus Kuscel) infestations are pyrethroids. However, pyrethroids are highly toxic to non‐target crayfish associated with rice–crayfish crop rotations. One solution to the near‐exclusive reliance on pyrethroids in a rice–crayfish pest management program is to incorporate neonicotinoid insecticides, which are insect specific and effective against weevils but not extremely toxic to crayfish. This study aimed to take the first step to assess neonicotinoids as alternatives to pyrethroids in rice–crayfish crop rotations by measuring the acute toxicities of three candidate neonicotinoid insecticides, clothianidin, dinotefuran and thiamethoxam, to juvenile Procambarus clarkii (Girard) crayfish and comparing them with the acute toxicities of two currently used pyrethroid insecticides, lambda‐cyhalothrin and etofenprox. RESULTS: Neonicotinoid insecticides are at least 2–3 orders of magnitude less acutely toxic (96 h LC₅₀) than pyrethroids to juvenile Procambarid crayfish: lambda‐cyhalothrin (0.16 µg AI L^?1) = etofenprox (0.29 µg AI L^?1) ? clothianidin (59 µg AI L^?1) > thiamethoxam (967 µg AI L^?1) > dinotefuran (2032 µg AI L^?1). CONCLUSION: Neonicotinoid insecticides appear to be much less hazardous alternatives to pyrethroids in rice–crayfish crop rotations. Further field‐level neonicotinoid acute and chronic toxicity testing with crayfish is needed. Copyright © 2009 Society of Chemical Industry     

六种新烟碱类杀虫剂残留在苹果实验室模拟加工中的变化

为明确苹果中残留的烯啶虫胺、噻虫嗪、吡虫啉、噻虫胺、呋虫胺和啶虫脒6种新烟碱类药剂在不同加工过程中的变化情况,采用高效液相色谱法研究了6种药剂在苹果实验室罐头、果酱、果酒和果醋模拟加工过程中的残留量变化。结果表明:在苹果罐头加工过程中,6种药剂在罐头中残留量与初始浓度相比均显著降低,其中吡虫啉和噻虫胺在罐头中的加工因子较高,均为0.8,啶虫脒在罐头中的加工因子最低,为0.1。罐头汁中烯啶虫胺的加工因子最高,为0.5,其次为啶虫脒和噻虫嗪,均为0.4。在果酱加工过程中,烯啶虫胺、噻虫嗪、吡虫啉、噻虫胺、呋虫胺和啶虫脒的加工因子分别为0.8、0.9、0.9、1.0、0.9和0.9。在果酒中除吡虫啉的加工因子为0.1外,其余药剂加工因子均小于0.1。在果醋中除噻虫胺有少量残留(0.05 mg/kg)外,其余药剂均低于检出限。6种新烟碱类药剂在苹果实验室模拟加工过程中,加工因子均小于1,残留降低。     

Correlated responses to neonicotinoid insecticides in clones of the peach-potato aphid, Myzus persicae (Hemiptera: Aphididae)

BACKGROUND: Although there are still no confirmed reports of strong resistance to neonicotinoid insecticides in aphids, the peach-potato aphid (Myzus persicae Sulzer) shows variation in response, with some clones exhibiting up to tenfold resistance to imidacloprid. Five clones varying in response to imidacloprid were tested with four other neonicotinoid molecules to investigate the extent of cross-resistance.RESULTS: All four compounds-thiamethoxam, thiacloprid, clothianidin and dinotefuran-were cross-resisted, with ED(50) values ranked in the same order as for imidacloprid. Resistance factors ranged up to 11 for imidacloprid, 18 for thiamethoxam, 13 for thiacloprid, 100 for clothianidin and 6 for dinotefuran.CONCLUSION: This variation in response does not appear to be sufficient to compromise the field performance of neonicotinoids aimed at controlling aphids. However, it highlights the need for careful vigilance and stewardship in all M. persicae populations, and a need to consider neonicotinoids as a single cross-resisted group for management purposes.     

Toxicity of systemic neonicotinoid insecticides to avocado thrips in nursery avocado trees

The efficacies of four systemic neonicotinoid insecticides applied to potted avocado trees at manufacturer-recommended rates were assessed against the avocado thrips, Scirtothrips perseae Nakahara. At the time of treatment, fully expanded first-flush young leaves were tagged for identification, and a proportion of these leaves was used in bioassays with second-instar thrips. At 7 weeks post-treatment, a second flush of leaves had fully expanded on the trees, and these leaves were included in additional bioassays comparing avocado thrips mortality on both first- and second-flush leaves. In bioassays with first-flush leaves, imidacloprid (273 mg AI pot(-1)) was the most effective insecticide, providing at least 70% mortality of thrips for 14 weeks. Thiamethoxam (137 mg AI pot(-1)), clothianidin (109 mg AI pot(-1)) and dinotefuran (241 mg AI pot(-1)) provided good control in bioassays that were conducted within 4 weeks of treatment, but thereafter their efficacies were inconsistent. In bioassays with second-flush leaves, imidacloprid provided at least 70% mortality up to 9 weeks after the insecticide application. Thereafter, mortality declined to 30% or lower. Bioassays with second-flush leaves collected from trees treated with thiamethoxam, clothianidin and dinotefuran resulted in unacceptably low thrips mortality. Monitoring of imidacloprid and thiamethoxam residues by ELISA showed that the greater persistence of imidacloprid in both first and second leaf flushes was due to a steadier uptake of this material. Although thiamethoxam residues rose quickly within the first leaf flush, levels had already begun to dissipate by the time the second leaf flush had started to develop.     

Toxicity of selected insecticides to <Emphasis Type="Italic">Trichogramma chilonis:</Emphasis> Assessing their safety in the rice ecosystem

Nine insecticides, namely, imidacloprid, thiamethoxam, chlorantraniliprole, clothianidin, pymetrozine, ethofenprox, BPMC, endosulfan, acephate, and the product Virtako® (Syngenta; chlorantraniliprole 20%?+?thiamethoxam 20%) were tested to determine their toxicity to the parasitoid Trichogramma chilonis using an insecticide-coated vial (scintillation) residue bioassay. All the insecticides tested showed different degrees of toxicity to the parasitoid. Thiamethoxam showed the highest toxicity to T. chilonis with an LC₅₀ of 0.0014 mg a.i. l ^?1, followed by imidacloprid (0.0027 mg a.i. l ^?1). The LC₅₀ values of acephate and endosulfan were 4.4703 and 1.8501 mg a.i. l ^?1, exhibiting low toxicity when compared with other insecticides tested. Thiamethoxam was found to be 3,195, 1,395 and 1,322 times more toxic than acephate, chlorantraniliprole and endosulfan, respectively, as revealed by the LC₅₀ values to T. chilonis. Based on risk quotient, which is the ratio between the field-recommended doses and the LC₅₀ of the beneficial, only chlorantraniliprole was found to be harmless to T. chilonis. The insecticides thiamethoxam, imidacloprid, Virtako®, ethofenprox and BPMC were found to be dangerous to the parasitoid. Since T. chilonis is an important egg parasitoid of leaf folders, reported to reduce the pest population considerably and often released augmentatively in rice IPM programs, the above noted dangerous chemicals should be avoided in the rice ecosystem.     

基于推荐用量分析我国新烟碱类杀虫剂的登记现状

本文对目前中国农药信息网上公布登记的吡虫啉、烯啶虫胺、啶虫脒、噻虫啉、噻虫嗪、噻虫胺、呋虫胺、氯噻啉、哌虫啶、环氧虫啶等10种新烟碱类杀虫剂的信息进行了查询,分别从登记剂型、作物、防治靶标等方面对这10种杀虫剂的登记推荐有效成分用量情况进行了统计分析,最后,挑选用量范围最大的3种有效成分,5种作物,5种靶标进行组合,并对可能的18种组合进行了数据分析。结果发现:1)在防治草坪-蛴螬和甘蔗-蔗螟上,吡虫啉的有效成分用量要明显高于噻虫嗪和噻虫胺两种药剂,最高分别为2 100.00和1 500.00 g/hm~2;2)在防治韭菜-韭蛆上,噻虫嗪的有效成分用量要明显高于吡虫啉和噻虫胺,最高为1 732.50 g/hm~2;3)在防治小麦-蚜虫方面,吡虫啉的推荐有效成分用量范围最大(相差120倍),且偏高数值点最多;4)在防治水稻-飞虱上,同样是吡虫啉的偏高数值点最多。为减少农药施用,建议在病虫防治时推荐应用有效成分用量较低的农药类型(包括推荐有效成分用量更低的农药剂型和生物活性更高的农药有效成分)。未来农药登记用量将在农药最低有效剂量研究的基础上,针对不同药剂在不同作物的特定防治靶标提出更加科学、合理的推荐用量,为我国农药的合理减施提供科学依据。     

Thiamethoxam acts as a target‐site synergist of spinosad in resistant strains of Frankliniella occidentalis

BACKGROUND: Previous studies have suggested that the resistance mechanism towards spinosad in Frankliniella occidentalis (Pergande) is an altered target site. Like the neonicotinoids, the spinosyns act on nicotinic acetylcholine receptors (nAChRs) in insects, but at a distinct site. The changes in nAChRs related to spinosad resistance in thrips might involve interaction with neonicotinoids. In this study, the efficacy of spinosad and neonicotinoids, alone and in combination, was evaluated in susceptible and spinosad‐resistant thrips strains. RESULTS: The neonicotinoids tested were imidacloprid, thiacloprid, acetamiprid, thiamethoxam and clothianidin. No cross‐resistance was shown between spinosad and any of the neonicotinoids. However, an increased toxicity was observed when a mixture of spinosad with thiamethoxam or clothianidin was tested. No synergism was found in the susceptible strains. The more spinosad‐resistant the thrips strain, the stronger was the synergism. CONCLUSION: Data suggest that spinosad and thiamethoxam may interact at the nAChRs in spinosad‐resistant thrips, facilitating enhanced insecticidal action. Copyright © 2012 Society of Chemical Industry     

Effect of distribution and concentration of topically applied neonicotinoid insecticides in buffalograss,Buchloe dactyloides,leaf tissues on the differential mortality of Blissus occiduus under field conditions

BACKGROUND: Neonicotinoid insecticides are generally efficacious against many turfgrass pests, including several important phloem‐feeding insects. However, inconsistencies in control of western chinch bugs, Blissus occiduus, have been documented in field efficacy studies. This research investigated the efficacy of three neonicotinoid insecticides (clothianidin, imidacloprid and thiamethoxam) against B. occiduus in buffalograss under field conditions and detected statistically significant differences in B. occiduus numbers among treatments. A subsequent study documented the relative quantity and degradation rate of these insecticides in buffalograss systemic leaf tissues, using HPLC. RESULTS: Neonicotinoid insecticides initially provided significant reductions in B. occiduus numbers, but mortality diminished over the course of the field studies. Furthermore, while all three neonicotinoids were present in the assayed buffalograss leaf tissues, imidacloprid concentrations were significantly higher than those of clothianidin and thiamethoxam. Over the course of the 28 day study, thiamethoxam concentrations declined 700‐fold, whereas imidacloprid and clothianidin declined only 70‐fold and 60‐fold respectively. CONCLUSIONS: Field studies continued to verify inconsistencies in B. occiduus control with neonicotinoid insecticides. This is the first study to document the relative concentrations of topically applied neonicotinoid insecticides in buffalograss systemic leaf tissues. Copyright © 2012 Society of Chemical Industry     

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.     

Comparison of foliar and soil formulations of neonicotinoid insecticides for control of potato leafhopper, Empoasca fabae (Homoptera: Cicadellidae), in wine grapes

BACKGROUND: The potential of systemic neonicotinoid insecticides to control potato leafhopper, Empoasca fabae (Harris), a damaging pest of wine grapes in the eastern United States, was investigated. Soil or foliar applications were made to potted or field‐grown vines, and the response of leafhoppers was determined in clip cages over the following month on young or mature leaves. RESULTS: Foliar application of imidacloprid caused immediate and long‐lasting reductions in E. fabae survival on both leaf ages, whereas the activity of soil‐applied imidacloprid was delayed. Clothianidin, imidacloprid and thiamethoxam all provided long‐lasting reduction in leafhopper survival on young and mature foliage when applied through either delivery route. However, the percentage of moribund nymphs was significantly greater on foliar‐treated vines and increased over time in mature and immature leaves compared with soil‐treated vines. Residue analysis of foliar‐applied imidacloprid showed an 89% decline in mature leaves from day 1 to day 27, and a 98% decline in immature leaves over the same time period. Comparison of soil‐applied clothianidin, imidacloprid and thiamethoxam in field‐grown vines showed significant reduction in E. fabae only on mature leaves of vines treated with thiamethoxam. CONCLUSIONS: Neonicotinoids can control E. fabae in small vines, even in rapidly expanding foliage where this pest causes greatest injury. Soil application provides superior long‐term vine protection because declining residues on foliar‐treated vines lead to suboptimal activity within 2–3 weeks. Vineyard managers of susceptible cultivars may take advantage of this approach to E. fabae management by using foliar applications of the three neonicotinoids tested here, or by using soil‐applied thiamethoxam. Copyright © 2011 Society of Chemical Industry     

Effect of thiamethoxam on cockroach locomotor activity is associated with its metabolite clothianidin

BACKROUND: In the present study, the effect of thiamethoxam and clothianidin on the locomotor activity of American cockroach, Periplaneta americana (L.), was evaluated. Because it has been proposed that thiamethoxam is metabolised to clothianidin, high‐performance liquid chromatography coupled with mass spectrometry was used to evaluate the amount of clothianidin on thiamethoxam‐treated cockroaches. RESULTS: One hour after neonicotinoid treatment, the time spent in the open‐field‐like apparatus significantly increased, suggesting a decrease in locomotor activity. The percentage of cockroaches displaying locomotor activity was significantly reduced 1 h after haemolymph application of 1 nmol g^?1 neonicotinoid, while no significant effect was found after topical and oral administration. However, at 24 and 48 h, all neonicotinoids were able to reduce locomotor activity, depending on their concentrations and the way they were applied. Interestingly, it was found that thiamethoxam was converted to clothianidin 1 h after application, but the amount of clothianidin did not rise proportionately to thiamethoxam, especially after oral administration. CONCLUSION: The data suggest that the effect of thiamethoxam on cockroach locomotor activity is due in part to clothianidin action because (1) thiamethoxam levels remained persistent 48 h after application and (2) the amount of clothianidin in cockroach tissues was consistent with the toxicity of thiamethoxam. Copyright © 2010 Society of Chemical Industry     

Resistance and cross-resistance to neonicotinoid insecticides and spinosad in the Colorado potato beetle, Leptinotarsa decemlineata (Say) (Coleoptera: Chrysomelidae)

The Colorado potato beetle, Leptinotarsa decemlineata (Say), has developed resistance to many insecticides used for its control, recently including imidacloprid, a neonicotinoid compound. Other neonicotinoids are now being deployed to control this pest. A key point in the strategies of resistance management is the monitoring of resistance and cross-resistance. In the summer of 2003, imidacloprid-resistant adult Colorado potato beetles collected from Long Island, New York, USA were bioassayed using topical applications of imidacloprid and nine other neonicotinoids. Compared to a standard susceptible strain, the Long Island beetles showed 309-fold resistance to imidacloprid, and lower levels of cross-resistance to all other neonicotinoids, despite these never having been used in the field, i.e., 59-fold to dinotefuran, 33-fold to clothianidin, 29-fold to acetamiprid, 28-fold to N-methylimidacloprid, 25-fold to thiacloprid, 15-fold to thiamethoxam, 10-fold to nitenpyram, but less than 2-fold to nicotine. In injection bioassays, high resistance to imidacloprid was also found (116-fold). Piperonyl butoxide partially suppressed resistance to imidacloprid, but the resistance level was still over 100-fold, indicating that other mechanisms were primarily responsible for resistance. Low levels of resistance (8- to 10-fold) were found to the nicotinic activator, spinosad, in an imidacloprid-resistant strain collected from the same field in 2004. The cross-resistance seen with all the neonicotinoids tested suggests that the rotation of imidacloprid with other neonicotinoids may not be an effective long-term resistance management strategy. Rotation with spinosad also carries some risk, but it is unlikely that spinosad resistance in this case is mechanistically related to that for the neonicotinoids.     

Susceptibility to neonicotinoids and risk of resistance development in the brown planthopper, Nilaparvata lugens (Stål) (Homoptera: Delphacidae)

BACKGROUND: In recent years, outbreaks of the brown planthopper, Nilaparvata lugens (Stål), have occurred more frequently in China. The objective of this study was to determine the susceptibility of N. lugens to neonicotinoids and other insecticides in major rice production areas in China. RESULTS: Results indicated that substantial variations in the susceptibility to different insecticides existed in N. lugens. Field populations had developed variable resistance levels to neonicotinoids, with a high resistance level to imidacloprid (RR: 135.3–301.3‐fold), a medium resistance level to imidaclothiz (RR: 35–41.2‐fold), a low resistance level to thiamethoxam (up to 9.9‐fold) and no resistance to dinotefuran, nitenpyram and thiacloprid (RR < 3‐fold). Further examinations indicated that a field population had developed medium resistance level to fipronil (up to 10.5‐fold), and some field populations had evolved a low resistance level to buprofezin. In addition, N. lugens had been able to develop 1424‐fold resistance to imidacloprid in the laboratory after the insect was selected with imidacloprid for 26 generations. CONCLUSION: Long‐term use of imidacloprid in a wide range of rice‐growing areas might be associated with high levels of resistance in N. lugens. Therefore, insecticide resistance management strategies must be developed to prevent further increase in resistance. Copyright © 2008 Society of Chemical Industry     

1.6%瑞香狼毒素水乳剂对4种蔬菜害虫的作用方式比较

采用叶片夹毒法、微量点滴法和玻片浸渍法等方法测定了1.6%瑞香狼毒素水乳剂对菜青虫、小菜蛾、豌豆蚜和截形叶螨的杀虫效果。结果表明:处理24h后,在触杀活性试验中,1.6%瑞香狼毒素水乳剂对试虫的毒力大小为菜青虫小菜蛾豌豆蚜截形叶螨;在内吸活性试验中,1.6%瑞香狼毒素水乳剂对截形叶螨和豌豆蚜的LC50分别为149.22mg/L和101.76mg/L,均小于触杀作用下的219.10mg/L和165.25mg/L,表明1.6%瑞香狼毒素水乳剂对豌豆蚜和截形叶螨内吸毒性明显优于触杀作用;在胃毒活性试验中,1.6%瑞香狼毒素水乳剂对菜青虫和小菜蛾的LC50分别为342.82mg/L和407.34mg/L,而触杀作用下的LC50为58.61mg/L和75.30mg/L,表明该药剂对菜青虫和小菜蛾有较强的触杀作用和一定的胃毒作用。     

Impact of neonicotinoid insecticides on natural enemies in greenhouse and interiorscape environments

The neonicotinoid insecticides imidacloprid, acetamiprid, dinotefuran, thiamethoxam and clothianidin are commonly used in greenhouses and/or interiorscapes (plant interiorscapes and conservatories) to manage a wide range of plant‐feeding insects such as aphids, mealybugs and whiteflies. However, these systemic insecticides may also be harmful to natural enemies, including predators and parasitoids. Predatory insects and mites may be adversely affected by neonicotinoid systemic insecticides when they: (1) feed on pollen, nectar or plant tissue contaminated with the active ingredient; (2) consume the active ingredient of neonicotinoid insecticides while ingesting plant fluids; (3) feed on hosts (prey) that have consumed leaves contaminated with the active ingredient. Parasitoids may be affected negatively by neonicotinoid insecticides because foliar, drench or granular applications may decrease host population levels so that there are not enough hosts to attack and thus sustain parasitoid populations. Furthermore, host quality may be unacceptable for egg laying by parasitoid females. In addition, female parasitoids that host feed may inadvertently ingest a lethal concentration of the active ingredient or a sublethal dose that inhibits foraging or egg laying. There are, however, issues that require further consideration, such as: the types of plant and flower that accumulate active ingredients, and the concentrations in which they are accumulated; the influence of flower age on the level of exposure of natural enemies to the active ingredient; the effect of neonicotinoid metabolites produced within the plant. As such, the application of neonicotinoid insecticides in conjunction with natural enemies in protected culture and interiorscape environments needs further investigation. Copyright © 2010 Society of Chemical Industry     

Effect of Bacillus thuringiensis subsp. israelensis and neonicotinoid insecticides on the fungus gnat Bradysia sp nr. coprophila (Lintner) (Diptera: Sciaridae)

The soil bacterium Bacillus thuringiensis Berliner subsp. israelensis (Bti), the neonicotinoid insecticides dinotefuran, imidacloprid, thiamethoxam and clothianidin and the insect growth regulator pyriproxyfen were evaluated to determine their efficacy against the larval stages of the fungus gnat Bradysia sp nr. coprophila (Lintner) in the laboratory. Treatments were applied as a drench to the growing medium in polypropylene deli containers. The Bti treatments had no effect on either instar tested, whereas all the other compounds negatively affected both the second and third instars. This study demonstrates that the soil bacterium B. thuringiensis var. israelensis may not be active on these larval stages, whereas the neonicotinoid insecticides and the insect growth regulator pyriproxyfen are effective on these stages. The fact that Bti is not effective on the second and third instars of the fungus gnat means that greenhouse producers using this insecticide must make applications before fungus gnat populations build up and before overlapping generations develop.