Brenner Robert, Prischmann-Voldseth Deirdre A
Department of Entomology 7650, North Dakota State University, Fargo, ND.
Environ Entomol. 2020 Apr 14;49(2):461-472. doi: 10.1093/ee/nvaa010.
Insecticidal neonicotinoid seed treatments are a common agricultural insect pest management strategy; however, effects on nontarget pests and omnivorous arthropods are understudied. We used a series of experiments to evaluate impacts of the neonicotinoid seed treatment thiamethoxam on densities of herbivorous twospotted spider mites (Tetranychus urticae Koch [Acari: Tetranychidae]) and feeding behavior of western flower thrips (Frankliniella occidentalis Pergande [Thysanoptera: Thripidae]), an omnivore that feeds on spider mite eggs but is also a significant plant pest. Spider mite densities were higher on neonicotinoid-treated soybeans, but only when mites were not spatially confined. We then examined how availability of thiamethoxam-treated food items (i.e., eggs from spider mites reared on treated soybeans, soybean leaf discs, or a combination of the two), and previous exposure to thiamethoxam-treated soybean impacted thrips feeding. Regardless of the presence of leaf tissue, thrips consumed fewer spider mite eggs laid by females reared on treated soybeans, suggesting spider mite eggs can serve as poisoned prey. Overall, thrips consumed less treated soybean leaf tissue, and thrips on treated leaf discs had a lower percentage of herbivorous feeding events and consumed more nontreated spider mite eggs, indicating a dietary shift from herbivory to predation. The neonicotinoid status of spider mite eggs and prior exposure of thrips also caused shifts in the number and size of leaf scars, likely as a result of altered foraging behavior and/or movement. Shifts between herbivory and predation have implications for thrips damage, virus transmission, and pest management, especially in systems with mixtures of nontreated and neonicotinoid-treated plants.
杀虫新烟碱类种子处理是一种常见的农业害虫管理策略；然而，其对非靶标害虫和杂食性节肢动物的影响尚未得到充分研究。我们通过一系列实验评估了新烟碱类种子处理剂噻虫嗪对草食性二斑叶螨（Tetranychus urticae Koch [蜱螨目：叶螨科]）密度以及西花蓟马（Frankliniella occidentalis Pergande [缨翅目：蓟马科]）取食行为的影响，西花蓟马是一种杂食性昆虫，以叶螨卵为食，但也是一种重要的植物害虫。在经新烟碱类处理的大豆上，叶螨密度更高，但仅在叶螨没有空间限制时如此。然后，我们研究了经噻虫嗪处理的食物（即取食经处理大豆的叶螨所产的卵、大豆叶盘或两者的组合）的可获得性，以及之前接触经噻虫嗪处理的大豆对蓟马取食的影响。无论是否存在叶片组织，蓟马取食经处理大豆上饲养的雌螨所产叶螨卵的数量都较少，这表明叶螨卵可作为有毒猎物。总体而言，蓟马取食经处理的大豆叶组织较少，在经处理叶盘上的蓟马食草性取食事件百分比更低，且取食更多未经处理的叶螨卵，这表明其饮食从食草转向了捕食。叶螨卵的新烟碱类状态以及蓟马之前的接触情况也导致了叶痕数量和大小的变化，这可能是觅食行为和/或移动改变的结果。食草和捕食之间的转变对蓟马危害、病毒传播和害虫管理具有影响，尤其是在未处理植物和经新烟碱类处理植物混合的系统中。
