烟碱类杀虫剂的应用、开发现状及展望

本文对烟碱类杀虫剂的开发现状及应用前景进行了简要的介绍。文中涉及烟碱类杀虫剂的化学结构、生物活性、登记和开发公司等。     

新烟碱类杀虫剂抗药性研究进展

新烟碱类杀虫剂是一类新开发的杀虫剂。研究表明，害虫野外种群对其敏感性差弄较大，现已有多种害虫对吡虫啉和啶虫脒产生了抗性。初步研究显示，马铃薯叶甲对吡虫啉抗性以不完全隐性的常染色体遗传；抗性似不稳定，交互抗性谱随虫种而变化，抗性形成可能与多功能氧化酶和酯酶有关。合理轮用和高剂量杀死策略是治理其抗性的有效措施。     

噻虫嗪和吡虫啉防治荔枝椿象若虫室内药效试验

本文采用喷雾法测定了新烟碱类杀虫剂噻虫嗪、吡虫啉对荔枝椿象若虫的室内防治药效。结果表明,噻虫嗪和吡虫啉对荔枝椿象若虫均有较高的防效,且噻虫嗪比吡虫啉的防效显著。使用30%噻虫嗪悬浮剂1 000倍液、2 000倍液,12 h荔枝椿象若虫的死亡率达100%。使用10%吡虫啉可湿性粉剂的1 000倍液、2 000倍液、3 000倍液,12 h荔枝椿象若虫的校正死亡率在28.3%~37%之间,24 h的校正死亡率在50%~61.7%之间,48h的校正死亡率在54.5%~89.1%。     

巴西允许空中喷洒新烟碱类杀虫剂

巴西当局最终推翻了7月份禁止空中喷施基于4种新烟碱类杀虫剂产品的预防性禁令。由于担心会对蜜蜂产生不利影响,此前环保部门Iba-ma发布了对基于吡虫啉、噻虫嗪、噻虫胺和氟虫腈农药产品的喷洒禁令(《Agrow》第645期第16页)。作为规范空中喷药的主管部门,农业部以及Ibama允许上述产品有条件用于大豆和甘蔗,除授权外,可以在2013年6月30日前无条件地用于大米和小麦。     

新烟碱类杀虫剂在苹果果实不同部位中的残留

为了明确噻虫嗪、烯啶虫胺、吡虫啉、啶虫脒、噻虫胺和呋虫胺6种新烟碱类杀虫剂在苹果果实不同部位中的迁移转化规律,以10年生红富士苹果树为试材,分别于蚜虫发生期 (7月10日) 和果实采收前1 d (9月25日) 通过整株喷雾施药,随机取样,采用高效液相色谱仪测定,外标法定量,分析各杀虫剂在生长期套袋果实和不套袋果实及储藏期果实不同部位中的残留量及迁移规律。结果表明:在果实套袋情况下,施药后72 h内果实不同部位各新烟碱类杀虫剂的含量均呈现先逐渐上升而后下降的趋势,且在果皮中的残留量最低 (均低于0.08 mg/kg),其中烯啶虫胺和吡虫啉在果皮中的残留量低于最低检测浓度,而在果柄和果肉中的残留量明显高于果皮中的,表明套袋果实中药剂主要来源于枝叶运输,经果柄进入果实后易向果肉累积;在果实未套袋情况下,施药后72 h 6种杀虫剂在果肉中的含量均高于套袋果实果肉中的,分别是套袋果实果肉中含量的7.75、3.52、3.36、6.57、2.92和3.06倍,表明套袋可有效降低果实中该类药剂的残留量。储藏试验结果表明:直接向果面喷施6种新烟碱类杀虫剂后,药剂主要存在于果皮中,施药后14和21 d在果肉中的含量均低于最低检测浓度,表明储藏期果皮为该类药剂的主要残留部位,且不易向果肉中转移。     

先正达/拜耳建言欧盟新烟碱类杀虫剂计划

为推动破解欧盟有关新烟碱类杀虫剂对蜜蜂健康"理论风险"僵局,先正达和拜耳提出一份行动计划建议。此举是在欧盟委员会就其一项有关2年内禁止在某些作物上使用噻虫胺、吡虫啉和噻虫嗪等新烟碱类杀虫剂     

烟粉虱细胞色素P450基因CYP6JM1的克隆及其在噻虫嗪抗性中的作用

烟粉虱Bemisia tabaci是全球性农业害虫之一, 目前采用的防治手段多为化学防治。噻虫嗪作为一种新烟碱类杀虫剂, 现被广泛应用于田间烟粉虱的防治, 但烟粉虱已对其产生了抗性。本文通过RT-qPCR对烟粉虱噻虫嗪抗性与敏感种群的细胞色素P450基因CYP6JM1表达水平进行了比较, 结果显示, 烟粉虱噻虫嗪抗性种群CYP6JM1基因表达水平明显升高。基因克隆和序列分析表明, CYP6JM1基因具备昆虫P450基因的典型特征。RT-qPCR检测结果表明, 该基因在烟粉虱1~2龄时期及腹部高水平表达。RNAi结果表明, 降低烟粉虱体内CYP6JM1基因的表达量能够显著提高其对噻虫嗪的敏感性, 表明CYP6JM1基因可能与烟粉虱对噻虫嗪的抗性有关。     

三种新烟碱类杀虫剂在土壤中的残留降解及影响因子

建立了吡虫啉、啶虫脒和噻虫嗪在土壤中的高效液相色谱-串联质谱（HPLC-MS/MS）检测方法。样品经乙腈提取和QuEChERS法净化后,采用HPLC-MS/MS检测,外标法定量,在0.01~1.0 mg/kg添加水平下,3种新烟碱类杀虫剂在土壤中的回收率在89%~103%之间,相对标准偏差（RSD）在1.3%~10.3%之间,定量限均为0.01 mg/kg。采用建立的方法,在室内模拟条件下,研究了土壤微生物、温度、土壤含水量及农药初始浓度对土壤中吡虫啉、啶虫脒和噻虫嗪降解的影响。结果表明:土壤微生物是影响农药残留降解的首要因素,灭菌处理土壤中农药残留降解速率明显低于非灭菌土壤。此外,环境温度、土壤含水量、初始浓度等因素也会对农药残留降解产生不同影响,土壤含水量为最大持水量的60%左右时降解最快,半衰期分别为15.6、7.2和25.8 d;农药初始浓度越高,降解速度越慢;在5~35℃范围内,随着温度的升高,降解速度加快。     

新型烟碱类杀虫剂啶虫脒研究进展

本文对新型氯化烟碱类杀虫剂啶虫脒在国内外的研究进展作了详细论述,并对其存在的问题和有效利用提出了一些见解和展望。     

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。     

吡虫啉和噻虫嗪对苜蓿盲蝽的防治效果及其在苜蓿中的残留

为了评价新烟碱类杀虫剂吡虫啉和噻虫嗪对苜蓿盲蝽的防治效果及安全性,采用田间喷雾法测定了20%吡虫啉可溶液剂(SL)和30%噻虫嗪悬浮剂(SC)对苜蓿盲蝽的防治效果,使用超高效液相色谱-串联质谱法(UPLC-MS/MS)测定了施药1、2、3次后(间隔7 d),药剂在苜蓿中的残留情况。结果表明,当吡虫啉和噻虫嗪在施药剂量分别为25.02 g/hm²和18.00 g/hm²时,药后3～7 d对苜蓿盲蝽的防治效果分别为80.01%～82.01%和77.54%～83.29%。吡虫啉和噻虫嗪连续施药3次后,在苜蓿中的最终残留量分别为1.90 mg/kg和0.08 mg/kg,吡虫啉已超过我国食品安全国家标准GB 2763-2021规定的果蔬中的最大残留限量(0.5 mg/kg)。因此建议每茬苜蓿生长期,可选用吡虫啉和噻虫嗪防治苜蓿盲蝽,吡虫啉和噻虫嗪喷施次数分别不宜超过2次和3次。     

Resistance and cross-resistance to imidacloprid and thiamethoxam in the Colorado potato beetle Leptinotarsa decemlineata

One of the major challenges in managing the Colorado potato beetle, Leptinotarsa decemlineata (Say) is its remarkable ability to develop resistance to virtually every insecticide that has ever been used against it. Resistance is particularly common throughout northeastern USA as far north as Maine. The first instances of resistance to imidacloprid have already been reported from several locations in New York, Delaware and southern Maine. Rotating insecticides with different modes of action may delay insecticide resistance, but successful implementation of this technique depends on a good understanding of resistance and cross-resistance patterns in populations of target pests. LC(50) values were measured for imidacloprid and thiamethoxam in Colorado potato beetle populations from a variety of locations in the USA and Canada using diet incorporation bioassays. The field performance of imidacloprid, thiamethoxam and clothianidin against imidacloprid-resistant beetles on a commercial potato farm in southern Maine was also evaluated. Correlation between LC(50) values for imidacloprid and thiamethoxam was highly significant, even when populations previously exposed to thiamethoxam were excluded from the analysis. There was no statistically detectable difference in the LC(50) values between populations exposed to both insecticides and to imidacloprid alone. Applications of neonicotinoid insecticides at planting delayed build-up of imidacloprid-resistant beetle populations on field plots by 1-2 weeks but failed to provide adequate crop protection. Consistently with bioassay results, there was also substantial cross-resistance among the three tested neonicotinoid insecticides. Results of the present study support the recommendation to avoid rotating imidacloprid with thiamethoxam as a part of a resistance management plan.     

Effectiveness of thiamethoxam and imidacloprid seed treatments against Bemisia tabaci (Hemiptera: Aleyrodidae) on cotton

BACKGROUND: Bemisia tabaci (Gennadius) biotype B is one of the most important pests on cotton around the world. Laboratory, greenhouse and field experiments were conducted to determine the efficacy of thiamethoxam and imidacloprid seed treatments against B. tabaci on cotton. RESULTS: Under laboratory conditions, the two treatments caused whitefly adult mortality, reduced oviposition and increased mortality of nymphs at 10, 20, 30 and 40 days after germination (DAG). The longer the adults fed on plants from treated seeds, the higher the mortality. The two treatments did not have any effect on eggs. The efficacy of the treated seeds against B. tabaci gradually decreased from 10 to 40 DAG, being the lowest at 40 DAG. In laboratory experiments, the efficacies between the two treatments were similar. In greenhouse experiments, the two treatments were equally effective with lower numbers of whiteflies than untreated controls. With both treatments the concentrations of the active ingredient were gradually reduced with aging of the plants and from the bottom to the top leaves of the plants. Numbers of live whiteflies were well correlated with the dosage of active ingredients. Under field conditions, the seeds treated with both insecticides exhibited similar efficacy against B. tabaci for up to ～2 months. CONCLUSION: Cotton seeds treated with imidacloprid and thiamethoxam were effective against B. tabaci for up to 45 days under laboratory and greenhouse conditions, and up to ～2 months under field conditions. Use of imidacloprid‐ and thiamethoxam‐treated seeds can be an important alternative for management of whiteflies on cotton. Copyright © 2010 Society of Chemical Industry     

Effect of imidacloprid on the reproduction of acaricide-resistant and susceptible strains of Tetranychus urticae Koch (Acari: Tetranychidae)

Occasional reports linking neonicotinoid insecticide applications to field population outbreaks of the two-spotted spider mite, Tetranychus urticae Koch, have been a topic of concern for integrated pest management (IPM) programmes, particularly in apples. In order to shed light on the factors which may contribute to the occasional field population increase of T. urticae following the application of neonicotinoid insecticides, greenhouse experiments have been set up. Four different T. urticae strains, namely GSS (acaricide-susceptible), WI (organophosphate-selected), USA (a largely uncharacterised strain) and Akita (METI (mitochondrial electron transport inhibitor) acaricide-resistant and cross-resistant to dicofol), were compared for their fecundity without insecticide treatment and for their ovipositional response to foliar and drench applications of the field-relevant dose of imidacloprid (100 mg litre(-1)). Without insecticide treatment, strain GSS laid significantly more eggs (162.50 (+/- 5.43)) than the multiple resistant strain Akita (139.90 (+/- 5.54)) during a 16 day oviposition period. With imidacloprid treatment the highest effect was observed with GSS, with a significantly reduced number of eggs in drench (143.40 (+/- 4.22)) and foliar (144.60 (+/- 5.85)) applications. For strains Akita and USA, no significant differences were observed in oviposition between imidacloprid treatments and controls. The proportion of F1 female offspring decreased significantly with drench application for GSS and WI, while no differences were observed among strains in the survival of F1 immature stages, except for strain USA. The viability of eggs was relatively high (from 82.9 (+/- 4.5)% for USA to 95.2 (+/- 1.2)% for GSS) and not affected by imidacloprid treatments.     

Spatial and temporal distribution of imidacloprid and thiamethoxam in citrus and impact on Homalodisca coagulata populations

Titers of two systemic neonicotinoid insecticides in citrus trees were measured in conjunction with conventional evaluations of their impact on glassy-winged sharpshooter (Homalodisca coagulata (Say); GWSS) populations. Xylem fluid samples were collected at regular intervals and from multiple locations within field-grown citrus trees to determine imidacloprid and thiamethoxam concentrations using commercial ELISA kits. Uptake profiles varied considerably with peak mean titers of imidacloprid occurring 6-8 weeks after application compared with 2 weeks for thiamethoxam. The persistence of each compound also varied as near-peak levels of imidacloprid were sustained for another 6-10 weeks before gradually declining. In contrast, thiamethoxam titers declined more rapidly after the initial peak, possibly reflecting an application rate only one-quarter of that used for imidacloprid. Within-tree distributions were more similar for the two compounds, with no significant effect due to height of the sample (upper or lower half) or to the quadrant location within the tree, with the exception of one quadrant in the thiamethoxam-treated trees. Substantial reductions in GWSS nymphs and adults were observed in imidacloprid-treated trees during the 2001 trial and were sustained for 4-5 months after treatment. Treatment effects on nymphs were not as well pronounced in the 2002 trial, when overall GWSS infestations were much reduced from the previous year. However, consistently lower adult infestations were still observed in 2002 for both treatments compared with untreated trees. Information on the spatial and temporal profiles in citrus trees was obtained for both compounds to complement field impact data and improve understanding of their pest management potential.     

Persistence and metabolism of imidacloprid in different soils of West Bengal

A laboratory experiment was performed to study the persistence of imidacloprid from two formulations (Confidor 200 g litre-1 SL and Gaucho 700 g kg-1 WS), and its metabolism in three different soils (Gangetic alluvial soil of Kalyani, lateritic soil of Jhargram and coastal alkaline soil of Canning) of West Bengal following application at 0.5 kg and 1.0 kg AIha-1. Dissipation of imidacloprid in soil followed first-order kinetics and DT50 values ranged from 28.7 to 47.8 days. The shortest half-lives (28.7 and 35.8 days) were observed in the lateritic soil of Jhargram for both liquid and powder formulations. The formation of two metabolites of imidacloprid, imidacloprid-urea and imidacloprid-olefin, was first detected on day 30 of degradation at 28 (+/- 1) degrees C in all three soils.     

Persistence,metabolism and safety evaluation of thiamethoxam in tomato crop

BACKGROUND: Thiamethoxam, a neonicotinoid insecticide, has been widely accepted for use in various crops, including vegetables, owing to its high efficacy against various chewing and sucking insect pests. In this particular study, the authors examined the residue dynamics of this insecticide in tomato and soil and calculated a safety index for this insecticide in an Indian context. RESULTS: In tomato fruits, the insecticide dissipated from 82 to 87% in 10 days with a half‐life of 4 days, whereas dissipation in soil, under tomato crop, varied between 72 and 75% in 15 days with a half‐life of 9 days. Total residues reached below detectable level in 15 days in tomato fruits and 20 days in soil. Maximum damage (30%) was found in control plots, as opposed to 8–10% of fruit damage in treated plots. One degradation product was detected on the tomato fruit surface, and three metabolites were identified in tomato fruits by the LC‐MS technique. The metabolites have been reported for the first time in tomato fruits. CONCLUSION: Thiamethoxam at normal and double the recommended use rate effectively controlled aphids, whiteflies and Helicoverpa, as the insect population decreased to a minimum within 10 days of spraying in comparison with the control. There was no significant difference between the two rates of application, and both thiamethoxam treatments significantly increased tomato fruit yield compared with the untreated control. A maximum residue limit (MRL) of 0.05 mg kg^?1 for tomato has been proposed, with a corresponding preharvest interval (PHI) of 8 days. These parallel advances in toxicology and analytical chemistry have strengthened the observations that thiamethoxam can be used safely and efficiently in crop protection programmes. Copyright © 2009 Society of Chemical Industry     

70%噻虫嗪种子处理可分散粉剂和10%吡虫啉可湿性粉剂拌种对马铃薯甲虫的防效

利用药剂拌种处理马铃薯种薯后播种的方法,研究比较了2种新烟碱类杀虫剂对马铃薯甲虫的活性和防治效果。结果表明,按药剂有效成分18 g/100 kg种薯拌种,70%噻虫嗪种子处理可分散粉剂拌种出苗后60 d对马铃薯甲虫幼虫的生物活性和防效较高,卵块孵化率较低,死亡率在61.1%以上,防效达57.3%,孵化率为36%,这有利于降低马铃薯甲虫种群数量,减轻为害。而10%吡虫啉可湿性粉剂拌种出苗后60d对马铃薯甲虫幼虫生物活性和防效较低,卵块孵化率较高,死亡率在12.5%以下,防效为37.1%,孵化率为64.6%,对马铃薯甲虫的控制效果较差。