Woods Joanna L, Richardson Briana J, Kaur Navneet, Dorman Seth J, Gent David H
U.S. Department of Agriculture-Agricultural Research Service, Forage and Cereal Research Unit, Corvallis, OR, USA.
Department of Botany and Plant Pathology, Oregon State University, Corvallis, OR, USA.
J Econ Entomol. 2025 Jun 13;118(3):1441-1445. doi: 10.1093/jee/toaf079.
Imidacloprid and other neonicotinoids have been associated with secondary pest outbreaks of twospotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae). Imidacloprid is commonly applied in hop for the suppression of various pest organisms. A 3-yr study was conducted in western Oregon to determine the impact of a single foliar application of imidacloprid on twospotted spider mites and their predators in hop when made in mid-May versus mid-June. Applications made in June generally resulted in greater densities of twospotted spider mites as compared to applications made in May or when plants were nontreated, although this effect was year-dependent. Predatory mites (Acari: Phytoseiidae) were present at low levels and seemingly were not impacted by imidacloprid application. Orius spp. (Hemiptera: Anthocoridae), Stethorus spp. (Coleoptera: Coccinellidae), and other macropredators were minimally reduced in one year on 2 dates. Given the small impact on the key predator groups, the mechanisms of imidacloprid-induced secondary outbreak of twospotted spider mite appears to involve factors other than direct toxicity to predators. Practically, avoiding the application of imidacloprid when twospotted spider mite densities are increasing (generally June) should minimize risk of secondary outbreaks of this organism.
吡虫啉和其他新烟碱类药剂与二斑叶螨（Tetranychus urticae Koch，蜱螨亚纲：叶螨科）的次要害虫爆发有关。吡虫啉通常用于啤酒花中以抑制各种害虫。在俄勒冈州西部进行了一项为期3年的研究，以确定在5月中旬与6月中旬对啤酒花进行一次叶面喷施吡虫啉对二斑叶螨及其捕食者的影响。与5月喷施或不喷施药剂的植株相比，6月喷施药剂通常会导致二斑叶螨的密度更高，不过这种影响因年份而异。捕食螨（蜱螨亚纲：植绥螨科）数量较少，似乎不受吡虫啉施用的影响。在一年中的2个日期，小花蝽属（半翅目：花蝽科）、食螨瓢虫族（鞘翅目：瓢虫科）和其他大型捕食者数量略有减少。鉴于对关键捕食者群体的影响较小，吡虫啉引发二斑叶螨二次爆发的机制似乎涉及除对捕食者直接毒性之外的其他因素。实际上，当二斑叶螨密度增加时（通常在6月）避免施用吡虫啉应可将该害虫二次爆发风险降至最低。
