In vivo and in vitro metabolism of fipronil by larvae of the European corn borer Ostrinia nubilalis

In vivo and in vitro metabolism of [14C]fipronil was examined in a susceptible European corn borer (Ostrinia nubilalis, Hübner) laboratory strain. [14C]Fipronil penetrated the larval integument slowly, with 71.5% of the applied radioactivity recovered from surface rinses 24 h after topical application. Despite this slow penetration, radioactivity was detected in both the excrement and internal organo-soluble fractions. Radioactivity in the internal aqueous fraction and tissue pellet accounted for less than 0.8% of total radioactivity. The in vivo studies suggest that fipronil oxidation to its sulfone metabolite is the major route of metabolic conversion. In vitro studies were performed using subcellular microsomal fractions isolated from European corn borer larval midguts. Cytochrome P450-dependent monooxygenase activity (methoxyresorufin O-demethylase) was consistently observed in midgut preparations, and formation and detection of the sulfone metabolite in the same midgut preparations was also NADPH-dependent and inhibited by piperonyl butoxide. In vitro metabolism results indicate microsomal monooxygenases are responsible for the conversion of fipronil to its sulfone form in the European corn borer.     

Postdiapause development and spring emergence of the european corn borer,Ostrinia nubilalis,in Israel

The European corn borer (ECB),Ostrinia nubilalis (Hübner) (Lepidoptera: Pyralidae), is the major pest of corn (Zea mays L.) in Israel. We investigated the temporal patterns of pupation and emergence of various overwintering ECB populations in Israel during 1992-94. The association between Julian date (JD) or cumulative degree-days (DD) and the rates of either pupation or emergence was studied using simple linear regression models. Differences between populations in JDs required to reach 50% pupation amounted to 5%, whereas for DD differences amounted to 26%. Similarly, at 50% emergence, differences between populations were up to 3% for JD and to 12% for DD. Two different forecasting models are proposed for either pupation or emergence. Based on these models, both pupation and emergence develop over a period of 4 to 5 weeks, and they are expected to occur between the following JDs: onset of pupation, 66–70 (March 7–11); 50% pupation, 96–102 (April 6–12); onset of emergence, 85–94 (March 26-April 4); and 50% emergence, 115–121 (April 25-May 1). Pupal development required 160 DD (confidence interval [C.I.] 141–179 DD) and it is expected to takeca 16 days (C.I. 14–18 days). The simple linear regression models obtained in this study are suggested as preliminary phenological models for the temporal prediction of postdiapause pupation and emergence of ECB.     

Evaluation of entomopathogenic nematodes for biocontrol of the european corn borer,Ostrinia nubilalis, on sweet corn in Israel

The potential of entomopathogenic nematodes for biological control of the European corn borer (ECB),Ostrinia nubilalis (Hübner), was evaluated under laboratory, screenhouse and field conditions. The ‘All’ and ‘Mexican’ strains ofSteinernema carpocapsae (Weiser) and the ‘HP88’ strain ofHeterorhabditis bacteriophora Poinar were compared in both dose response assays (5, 50 and 500 infective juveniles [IJ] per petri dish containing five 5th-instar ECB eggs; 72 h of incubation) and exposure time assays (3, 6 and 9 h of incubation). In the dose response assays the highest rates of ECB killing resulted from infestation with the Mexican strain ofS. carpocapsae. In the exposure time assays there were no significant differences between the killing rates of the three nematode strains. Sweet corn plants(Zea mays var.saccharata) grown in a screenhouse, were infested with ECB neonates and 4 days later sprayed with a suspension of the Mexican strain ofS. carpocapsae (50,000 IJ per plant). The number of ECB larvae found on treated corn plants after one week was significantly (P=0.05) lower (3- to 5-fold) than the number found on untreated plants. Similar treatment in the field significantly reduced the rate of economic ear damage from 20% to 5%. Contribution from the Agricultural Research Organization. No. 2260-E, 1997 series     

Inhibition of pheromone response in Sesamia nonagrioides by the pheromone of the sympatric corn borer, Ostrinia nubilalis

Sesamia nonagrioides Lef. and Ostrinia nubilalis (Hübn.) are two corn borers present in the Mediterranean area that share a similar feeding habitat. The female sex pheromones of the two species consist of (Z)-11-hexadecenyl acetate, (Z)-11-hexadecen-1-ol, (Z)-11-hexadecenal and dodecyl acetate (77:8:10:5 w/w) and (Z)-11-tetradecenyl acetate and (E)-11-tetradecenyl acetate (97:3 w/w) respectively. Although the pheromones share no common components, previous work had shown the inhibition of the response by O. nubilalis males to their own pheromone owing to the presence of S. nonagrioides pheromone. In this study, the pheromone of O. nubilalis and its two components separately were shown to inhibit the attraction of S. nonagrioides males to the synthetic female pheromone in both laboratory wind-tunnel bioassay and field trapping studies. In the wind tunnel, the number of contacts of S. nonagrioides males with the source were significantly (P < 0.05) reduced by the single pheromone components of O. nubilalis. In the field, the addition of 1% of O. nubilalis pheromone significantly (P < 0.05) reduced the catches of S. nonagrioides males. The components of both pheromones also elicited electroantennographic responses from antennae of male S. nonagrioides moths. The ecological consequences and the possibilities of applying this cross-inhibition for mating disruption techniques are discussed.     

Activity of gut proteinases from Cry1Ab-selected colonies of the European corn borer, Ostrinia nubilalis (Lepidoptera: Crambidae)

Susceptibility to the Cry1Ab protoxin and toxin from Bacillus thuringiensis (Berliner) and activity of gut proteinases were assessed in both susceptible and Cry1Ab-selected colonies of European corn borer, Ostrinia nubilalis (Hubner). Resistance in two different selected colonies was at least 6- and 15-fold for the Cry1Ab protoxin and 108- and 484-fold for the Cry1Ab toxin. Activities of trypsin-like, chymotrypsin-like and elastase-like proteinases were variable among the colonies tested and not indicative of a major contribution to Cry1Ab resistance. Activation of the 130-kDa Cry1Ab protoxin occurred rapidly in all colonies, with no apparent differences among colonies. In addition, there were no apparent changes in activated Cry1Ab processing, indicating that proteolytic degradation was not associated with resistance. These results suggest that mechanisms other than proteolytic activation of protoxin and toxin degradation, such as target site modification may be involved in the resistance to B thuringiensis Cry1Ab in these O nubilalis colonies.     

Topical, residual and ovicidal contact toxicity of three reduced-risk insecticides against the European corn borer, Ostrinia nubilalis (Lepidoptera: Crambidae), on potato

BACKGROUND: The goal of the research was to gather efficacy data required to introduce reduced-risk insecticides in sustainable control programs for European corn borer, Ostrinia nubilalis Hubner, on potato. RESULTS: Laboratory tests confirmed that sprays of indoxacarb and novaluron at recommended field rates are as effective as spinosad against neonate larvae of O. nubilalis. However, there is evidence that higher rates would enhance the inhibition of chitin synthesis by novaluron. The three insecticides showed ovilarvicidal activity when applied to O. nubilalis egg masses 2 days prior to black head stage. The ovicidal activity of spinosad and novaluron was almost twice that of indoxacarb. At the recommended field rates, the residues of the three insecticides displayed contact toxicity to O. nubilalis larvae. Spinosad residues 16 h old or less provided the highest immediate (24 h after exposure) contact mortality, followed by indoxacarb and then by novaluron. Also, residues of spinosad had faster contact efficacy than indoxacarb, which had faster efficacy than novaluron. CONCLUSION: Spinosad, indoxacarb and novaluron have ovicidal properties, which could enhance O. nubilalis management programs. However, the contact residual toxicity is limited in duration and would likely only play a minor role in O. nubilalis control.     

北方春玉米区亚洲玉米螟对Bt玉米的抗性风险分析

为了解我国北方春玉米区种植Bt玉米条件下主要靶标害虫亚洲玉米螟Ostrinia furnacalis的Bt抗性风险,探索合理的Bt玉米种植比例,根据亚洲玉米螟的特点构建种群动态与遗传模型,对不同的Bt玉米种植比例进行分析评估。结果显示,当以种子混合种植75%的Bt玉米+25%的非Bt玉米庇护所时,亚洲玉米螟的种群控制时间,即亚洲玉米螟种群密度下降到每百株玉米植株30头幼虫以下的时间,为1～2年,而害虫的抗性时间,即亚洲玉米螟种群抗性基因频率达到50%的时间,在1代区为40年、在2代区为20年。当以种子混合种植20%、15%、10%、5%的非Bt玉米庇护所时,亚洲玉米螟的种群控制时间仍为1～2年,而害虫的抗性时间缩短,在1代区分别是29、21、15、9年,在2代区分别是14、10、7、4年。表明在研究区域内以种子混合种植20%以上的非Bt玉米庇护所可维持对亚洲玉米螟的Bt抗性管理至少14年。     

美国杀鼠剂的登记应用现状

目前在美国环保署登记应用的杀鼠剂商品共有302个,有效成分13种。其中磷化锌、氯鼠酮、敌鼠酮、α-氯代醇和马钱子碱等全部或部分产品被列入限制使用农药产品名录,和其他限制使用农药一样受到限制使用政策的约束。同时,美国杀鼠剂产品的销售、流通和使用主要受到EPA《杀鼠剂风险消减决定》的限制,特别是第二代抗凝血类药剂只允许在特定专业领域流通和使用。     

杀虫剂对转Bt水稻靶标害虫二化螟和非靶标害虫稻飞虱种群数量的影响

为明确杀虫剂对转Bt水稻品种华恢1号(Huahui 1,HH1)靶标害虫二化螟Chilo suppressalis及其非靶标害虫白背飞虱Sogatella furcifera和褐飞虱Nilaparvata lugens种群数量的影响,于2014—2015年在江西省南昌市南昌县莲塘镇的广福试验基地进行田间试验,种植转Bt水稻和对照亲本水稻,分别对其进行施用杀虫剂和未施用杀虫剂处理,然后对经2种处理后转Bt水稻和对照亲本水稻田中靶标害虫二化螟幼虫数量及非靶标害虫白背飞虱、褐飞虱的若虫数量、成虫数量、总虫量(若虫数量和成虫数量之和)进行调查,并对这3种害虫田间种群数量的年份、水稻品种、杀虫剂影响因子进行方差分析。结果显示,转Bt水稻种植对二化螟幼虫数量影响显著,而施用杀虫剂处理未显著影响二化螟幼虫数量。转Bt水稻种植对白背飞虱和褐飞虱的若虫数量、成虫数量和总虫量无显著影响;而施用杀虫剂处理显著降低转Bt水稻及其对照亲本水稻稻田内白背飞虱和褐飞虱的若虫数量及总虫量,并显著降低白背飞虱成虫数量。2014年和2015年,施用杀虫剂和未施用杀虫剂转Bt水稻田内二化螟幼虫数量极低或未调查到;未施用杀虫剂转Bt水稻上二化螟幼虫数量仅在2014年显著低于未施用杀虫剂对照亲本水稻。2014年,未施用杀虫剂转Bt水稻和对照亲本水稻上白背飞虱总虫量最大值分别为1 037、1 376头/百丛,施用杀虫剂后分别降低至233、253头/百丛;未施用杀虫剂转Bt水稻上和对照亲本水稻上褐飞虱总虫量最大值分别为4 120、2 413头/百丛,施用杀虫剂后降低至367、410头/百丛;2015年白背飞虱和褐飞虱的发生规律与2014年相同。表明转Bt水稻可显著降低二化螟幼虫数量,但褐飞虱及白背飞虱数量没有降低,而施用杀虫剂可有效降低褐飞虱及白背飞虱数量。     

甜玉米玉米螟的发生危害与防治措施

研究了吉林省公主岭地区甜玉米上亚洲玉米螟Ostrinia furnacalis(Guene)的发生危害和防治措施。田间抗螟性人工接虫鉴定结果表明,甜玉米710A和普通玉米自交系丹340的食叶级别为9级,即高感玉米螟,而单交种邢抗5号和邢抗2号的食叶级别为5级,为中抗型。与普通感虫和中等抗虫性玉米品种相比,取食甜玉米的玉米螟幼虫存活率高3～7倍,发育速度更快,提前约4～8天(1～2个龄期),说明甜玉米比普通玉米感虫。甜玉米比普通玉米及早播比晚播田更吸引玉米螟产卵。田间小区试验表明,化学杀虫剂的防治效果比白僵菌和苏云金杆菌的好,以氯菊酯喷雾防治效果最好,虫孔减退率达90％;其次是杀螟灵颗粒剂、Bt喷雾和Bt颗粒剂;而白僵菌的防治效果较差,喷雾防治效果好于颗粒剂。大田防治效果与小区试验基本相同。同时还分析了氯菊酯防治甜玉米玉米螟的防治策略、防治时期、施用次数等。此外,对Bt制剂作为化学杀虫剂的取代品及与其它生物防治方法协调使用的优点与潜力进行了讨论。     

玉米根萤叶甲的抗逆性与防治研究进展

玉米根萤叶甲（Diabrotica virgifera virgifera Leconte）在美国是最重要的玉米害虫。它不仅对一些环戊二烯、有机磷类和氨基甲酸盐类化学杀虫剂产生了很强的抗药性,还对玉米 大豆轮作和调整播期等农业防治措施产生了适应性。此外,该虫有较广的适生性和扩展性。在过去的60年内,它从美国中西部传到了东北部沿海地区,并入侵欧洲定殖为害。新近采用的防治方法主要是种植转Bt基因抗虫玉米。表达经生物工程改良并导入的某个Bt毒素基因如Cry3Bb1、Cry34Ab1/Cry35Ab1或mCry3A的转基因抗虫玉米可毒杀取食的玉米根萤叶甲。但在转Bt基因玉米使用数年后,田间观察和温室筛选研究显示,玉米根萤叶甲具有对转基因玉米的潜在抗性。本文对该叶甲与防治有关的生物学特性、抗逆性及其机制、防治措施做了综述和讨论,旨在对该害虫的检疫防除有所帮助。