Toxicity of thiamethoxam to Tetranychus urticae Koch and Phytoseiulus persimilis Athias-Henriot (Acari Tetranychidae, Phytoseiidae) through different routes of exposure

BACKGROUND: Knowledge of the impact of insecticides on Tetranychus urticae Koch and its predator Phytoseiulus persimilis Athias‐Henriot is crucial for IPM. This study evaluates the effect of thiamethoxam on T. urticae and its predator by considering different routes of exposure (topical, residual and contaminated food exposures) and their combinations. RESULTS: Thiamethoxam effects on T. urticae were higher when residual and contaminated food exposures were considered. The total effect was higher than 90% where contaminated food exposure was involved. On P. persimilis, the total effect was higher in residual and contaminated prey exposures compared with topical exposure, and all combinations of routes of exposure attained a total effect higher than 90%. CONCLUSION: Thiamethoxam was found to be toxic to T. urticae and P. persimilis; however, the impact of the insecticide depended on the routes of exposure and their combinations. Lethal and sublethal effects occurred in residual and contaminated food exposures, while only sublethal effects occurred in topical exposure of predators and prey. The toxicity of thiamethoxam on prey and predator increased with the number of exposure routes involved. By limiting exposure to thiamethoxam to ingestion of contaminated food only, the impact of the pesticide was more favourable to P. persimilis than to its prey. Copyright © 2010 Society of Chemical Industry     

温度对以朱砂叶螨为食的加州新小绥螨实验种群参数的影响

在19、22、25、28和31℃5种温度条件下,研究了加州新小绥螨[Neoseiulus californicus(McGregor)]国内种群以朱砂叶螨[Tetranychus cinnabarinus(Boisduval)]为猎物的实验种群参数。在19~31℃温度范围内,随着温度的升高,加州新小绥螨世代发育历期和种群倍增时间缩短,在31℃下,世代历期和种群倍增时间最短,分别为5.69d和2.537 2d。净增殖率在25℃时最大,为26.707 7。内禀增长率(rm)和周限增长率(λ)随着温度的升高而增大,在31℃时为最大,分别为0.273 2和1.314 2。在28℃时性比(♀/(♀+♂))最大,为0.642 4。在28℃时,平均每雌产卵数最大,为46.6粒/雌。加州新小绥螨国内种群捕食朱砂叶螨的发育和繁殖生物学特性表明该捕食螨具有重要的生物防治潜能。     

加州新小绥螨对猕猴桃卢氏叶螨的捕食作用

为明确加州新小绥螨对卢氏叶螨的捕食潜力,采用捕食功能反应研究了加州新小绥螨对卢氏叶螨各螨态的捕食作用。结果表明,在19～31℃温度下,加州新小绥螨对卢氏叶螨的捕食作用属于Holling Ⅱ型,28℃时捕食能力最强,a/Th为51.9750;对卵、幼螨和若螨的选择系数分别为0.87、0.90、1.22;对各螨态的控制能力大小依次是幼螨 >卵 >若螨。同一密度下,加州新小绥螨对卢氏叶螨若螨的寻找效应随着温度的升高先增大后减小,28℃时最大,为0.9074;同一温度下,寻找效应随猎物密度的增加而减小,猎物密度为16头时最小,为0.3367。加州新小绥螨对猕猴桃卢氏叶螨具有较强的捕食能力,具有开发利用价值。     

球孢白僵菌对二斑叶螨的致病性和对天敌智利小植绥螨的间接影响

二斑叶螨是世界性害螨,为害多种经济作物和蔬菜.为明确球孢白僵菌和捕食螨联合应用防控二斑叶螨的可行性,本文测定了不同浓度球孢白僵菌GZGY-1-3孢子悬浮液对二斑叶螨的致病力,并用喷施球孢白僵菌16h、24h、36h和48h后的二斑叶螨分别饲喂智利小植绥螨,测定智利小植绥螨连续两代的致死率、生长发育及繁殖力变化.结果表明...     

Acetylcholinesterase point mutations in European strains of Tetranychus urticae (Acari: Tetranychidae) resistant to organophosphates

BACKROUND: In Tetranychus urticae Koch, acetylcholinesterase insensitivity is often involved in organophosphate (OP) and carbamate (CARB) resistance. By combining toxicological, biochemical and molecular data from three reference laboratory and three OP selected strains (OP strains), the AChE1 mutations associated with resistance in T. urticae were characterised. RESULTS: The resistance ratios of the OP strains varied from 9 to 43 for pirimiphos‐methyl, from 78 to 586 for chlorpyrifos, from 8 to 333 for methomyl and from 137 to 4164 for dimethoate. The insecticide concentration needed to inhibit 50% of the AChE1 activity was, in the OP strains, at least 2.7, 55, 58 and 31 times higher for the OP pirimiphos‐methyl, chlorpyrifos oxon, paraoxon and omethoate respectively, and 87 times higher for the CARB carbaryl. By comparing the AChE1 sequence, four amino acid substitutions were detected in the OP strains: (1) F331W (Torpedo numbering) in all the three OP strains; (2) T280A found in the three OP strains but not in all clones; (3) G328A, found in two OP strains; (4) A201S found in only one OP strain. CONCLUSIONS: Four AChE1 mutations were found in resistant strains of T. urticae, and three of them, F331W, G328A and A201S, are possibly involved in resistance to OP and CARB insecticides. Among them, F331W is probably the most important and the most common in T. urticae. It can be easily detected by the diagnostic PCR‐RLFP assay developed in this study. Copyright © 2009 Society of Chemical Industry     

基于两性生命表的以朱砂叶螨为猎物的加州新小绥螨四川种群生长发育、繁殖及捕食率

为全面掌握加州新小绥螨四川种群的种群特征,本试验运用两性生命表开展了以朱砂叶螨为猎物的加州新小绥螨四川种群的生长发育、繁殖与捕食率研究。结果表明,加州新小绥螨四川种群不同发育阶段重叠,在雌成螨产卵期结束前雌成螨特定年龄-阶段存活率S_xj明显高于雄成螨。单位时间（12 h）特定年龄-阶段繁殖力f_x5、特定年龄繁殖力m_x最大值分别为1.74和1.12粒/雌,单雌总产卵量为49.28粒。种群内禀增长率为0.27/d、周限增长率为1.31/d、净增殖率为26.61粒/个体、世代平均周期为12.34 d。在未成熟阶段,加州新小绥螨各螨态特定年龄-阶段捕食率C_xj均呈双峰型,雌成螨和雄成螨捕食率均随时间明显波动。加州新小绥螨取食朱砂叶螨的转化率为4.55、内禀捕食率为0.54、周限捕食率为1.72头。以朱砂叶螨为猎物时,加州新小绥螨四川种群表现出较好的个体发育、种群增长和捕食能力,可作为控制朱砂叶螨的生防资源,值得进一步研究和开发利用;同时朱砂叶螨可作为加州新小绥螨四川种群人工繁殖选择的猎物之一。     

哒螨灵对加州新小绥螨的安全性和捕食能力的影响

本文在评估哒螨灵对加州新小绥螨Neoseiulus californicus(McGregor)安全性的基础上,测定了经该药剂处理后的捕食螨对朱砂叶螨Tetranychus cinnabarinus(Boisduval)的捕食功能反应.结果表明,哒螨灵对朱砂叶螨和加州新小绥螨的致死中浓度(LC50)分别为17.62μg...     

加州新小绥螨对猎物的选择行为及其扩散行为

本文研究了柑橘全爪螨Panonychus citri （McGregor）不同螨态及其丝网对加州新小绥螨Neoseiuluscalifornicus的吸引作用和影响加州新小绥螨扩散行为的因素。结果表明,柑橘全爪螨完整丝网对加州新小绥螨吸引最强,在试验的5 h中,对加州新小绥螨吸引作用在第1 h效果显著,第2~5 h效果极显著,其中第3 h时的吸引作用最强达78.33%;柑橘全爪螨雌成螨、若螨和幼螨对加州新小绥螨均具有不同强度的吸引能力,吸引作用最强时分别达76.67%、71.67%和68.33%;猎物密度影响不同取食经历下加州新小绥螨的扩散行为,其扩散时间与生境中的柑橘全爪螨卵初始密度呈正相关,处于饥饿状态和自身密度较高时会加速加州新小绥螨的扩散行为,加州新小绥螨雌后若螨扩散时间低于加州新小绥螨雌成螨。     

Efficacy of five selected acaricides against Tetranychus urticae (Acari: Tetranychidae) and their side effects on relevant natural enemies occurring in citrus orchards

BACKGROUND: Three groups of natural enemies are fundamental in citrus IPM in Spain: coccinellid and phytoseiid predators and hymenopteran parasitoids. Tetranychus urticae Koch is an important pest affecting citrus, for which biological control has not yet been achieved; therefore, acaricides are commonly used to control it. The goal of this study was to measure the efficacy of different acaricides on this mite and their side effects on three natural enemies relevant for citrus (Cryptolaemus montrouzieri Mulsant, Neoseiulus californicus McGregor and Aphidius colemani Viereck).RESULTS: Some products proved highly effective against T. urticae and harmless to A. colemani (mineral oil, tebufenpyrad, clofentezine and fenazaquin). However, almost all products tested were slightly harmful for both the predators considered. Fenazaquin was even moderately harmful for N. californicus. CONCLUSION: Further studies, like that presented here, are necessary to gain a better understanding of integrating biological and chemical controls. When considering both efficacy and side effects on beneficial arthropods, the best options would seem to be mineral oil, tebufenpyrad and clofentezine. However, it is urgent to complete testing of the side effects of the acaricides used in citrus. This question is crucial if the fact that two recently introduced Tetranychidae are being controlled in citrus by chemical means exclusively is considered.     

Fenpyroximate resistance in Tetranychus urticae (Acari: Tetranychidae): cross-resistance and biochemical resistance mechanisms

A field colony of the Two-spotted spider mite, Tetranychus urticae (Koch), resistant to fenpyroximate was further selected with fenpyroximate 5SC for 20 generations at a selection pressure of 30-50% mortality (designated as FR-20 strain). Resistance and cross-resistance levels of the FR-20 strain to 18 acaricides were determined using a spray method. The FR-20 strain was extremely resistant to fenpyroximate [resistance ratio (RR) 252]. The strain exhibited extremely strong positive cross-resistance to acrinathrin (RR 196), and high levels of resistance to benzoximate (RR 55) and propargite (RR 64). Moderate levels of cross-resistance (RR 11-40) to abamectin, fenbutatin oxide, fenpropathrin, pyridaben, pyridaben + bifenthrin and tebufenpyrad were observed. The FR-20 strain showed low levels of resistance (RR < 10) to azocyclotin, bromopropylate, chlorfenapyr, chlorfenapyr + bifenthrin, chlorfenapyr + pyridaben, dicofol, fenazaquin and milbemectin. Synergist experiments with different metabolic inhibitors revealed that piperonyl butoxide had the greatest effect on the efficacy of fenpyroximate, followed by iprobenfos and triphenyl phosphate. In a comparative assay with detoxifying enzymes, the FR-20 strain showed 2.5-fold higher activity in p-nitroanisole-O-demethylation, and 2.5- and 2.2-fold higher activities in alpha- and beta-naphthyl acetate hydrolysis, respectively. These results suggested that enhanced activities of both mixed-function oxidases and esterases likely contribute to the fenpyroximate resistance of the FR-20 strain of T urticae.     

变温和光周期对加州新小绥螨性别分化及繁殖的影响

本研究以朱砂叶螨为猎物,研究了在23℃/13℃、26℃/16℃、29℃/19℃、32℃/22℃和35℃/25℃五个变温和14L：10D、12L：12D和10L：14D三个光周期共15个组合对加州新小绥螨性比分化及繁殖的影响。明确32℃/22℃的变温与光周期14L：10D组合的雌性比最高,为78.38%。其次为32℃/22℃的变温和光周期10L：14D的组合,为77.32%;32℃/22℃的变温和光周期10L：14D组合的每雌平均产卵量最高为91.12,显著高于32℃/22℃的变温和光周期14L：10D的每雌平均产卵量43.55。32℃/22℃的变温和光周期10L：14D组合利于加州新小绥螨种群发展。该研究结果为规模繁育加州新小绥螨,实现种群快速增长提供了重要理论依据。     

Prey stage preference,mutual interference and switching of Amblyseius swirskii (Acari: Phytoseiidae) on Eotetranychus frosti (Acari: Tetranychidae) and Cenopalpus irani (Acari: Tenuipalpidae)

Abstract

Prey stage preference, mutual interference, and switching of Amblyseius swirskii Athias-Henriot on Eotetranychus frosti (McGregor) (Tetranychidae) and Cenopalpus irani Dosse (Tenuipalpidae) were evaluated under laboratory conditions on apple leaves. The results of no-choice experiments on the two prey revealed that the predator A. swirskii consumed significantly more eggs than other prey stages. The predator consumed about 46% and 57% of the initial density of eggs of E. frosti and C. irani, respectively. In choice experiments the mean consumption rate of A. swirskii females significantly differed among each of the pests’ life stages. The negative value of the interference coefficient in the mutual interference analysis showed an inverse relationship between the predator density and per capita searching efficiency. The prey preference by predator was not dependent on the relative abundance of prey, as it did not switch from of E. frosti when it became rare to another prey which was more abundant except for the ratio 20E. frosti:60C. irani. The results of this study revealed that A. swirskii could be utilized as an effective predator in the integrated management of E. frosti and C. irani; particularly, its heavy preference for E. frosti could play a considerable role in control of it.     

Toxicity of the herbicide glufosinate-ammonium to Tetranychus urticae (Acari: Tetranychidae) under laboratory and field conditions

The toxicity of herbicides widely used in apple orchards to the two-spotted spider mite (Tetranychus urticae) was evaluated in laboratory and field studies. In a laboratory study with susceptible T. urticae, glufosinate-ammonium was highly effective against larvae, protonymphs and adults, but non-toxic to eggs. Its efficacy was much greater than that of the commonly used acaricide azocyclotin. The immatures died within 24 h after treatment, suggesting that the nymphicidal action may be attributable to a direct effect rather than an inhibitory action of chitin synthesis. Glufosinate-ammonium showed a positive temperature coefficient of toxicity against T. urticae adults at six temperatures from 10 to 32°C, being more toxic at higher temperatures. Very low levels of resistance to the herbicide were observed in the seven field-collected T. urticae populations resistant to various acaricides. Treatment with glufosinate-ammonium did not cause a repellent response from either adults or immature stages of T. urticae. Paraquat dichloride and glyphosate were ineffective against all stages of T. urticae. In a field study of a population of T. urticae, glufosinate-ammonium when sprayed to weeds caused significant decrease in T. urticae population densities in apple trees for nine weeks after treatment, as compared with the control. Thereafter, a single application of standard acaricides to apple foliage greatly reduced population densities, although there was no difference in the densities between the glufosinate-ammonium-treated and control plots. Based upon laboratory and field data, two single treatments with glufosinate-ammonium to weeds in May and a selective acaricide to apple trees in July may be used to prevent damage by T. urticae. ©1997 SCI