Departamento de Entomologia, Universidade Federal de Viçosa, Viçosa, MG 36570-000, Brazil.
Chemosphere. 2013 Oct;93(6):1111-6. doi: 10.1016/j.chemosphere.2013.06.030. Epub 2013 Jul 3.
Secondary pest outbreak is a counterintuitive ecological backlash of pesticide use in agriculture that takes place with the increase in abundance of a non-targeted pest species after pesticide application against a targeted pest species. Although the phenomenon was well recognized, its alternative causes are seldom considered. Outbreaks of the southern red mite Oligonychus ilicis are frequently reported in Brazilian coffee farms after the application of pyrethroid insecticides against the coffee leaf miner Leucoptera coffeella. Selectivity favoring the red mite against its main predatory mites is generally assumed as the outbreak cause, but this theory has never been tested. Here, we assessed the toxicity (and thus the selectivity) of deltamethrin against both mite species: the southern red mite and its phytoseid predator Amblyseius herbicolus. Additionally, behavioral avoidance and deltamethrin-induced hormesis were also tested as potential causes of red mite outbreak using free-choice behavioral walking bioassays with the predatory mite and life-table experiments with both mite species, respectively. Lethal toxicity bioassays indicated that the predatory mite was slightly more susceptible than its prey (1.5×), but in more robust demographic bioassays, the predator was three times more tolerant to deltamethrin than its prey, indicating that predator susceptibility to deltamethrin is not a cause of the reported outbreaks. The predator did not exhibit behavioral avoidance to deltamethrin; however insecticide-induced hormesis in the red mite led to its high population increase under low doses, which was not observed for the predatory mite. Therefore, deltamethrin-induced hormesis is a likely cause of the reported red mite outbreaks.
次要害虫暴发是农业中使用杀虫剂带来的一种反直觉的生态反弹，即在针对目标害虫物种使用杀虫剂后，非目标害虫物种的丰度会增加。尽管这种现象已经得到了很好的认识，但很少考虑其替代原因。在巴西咖啡农场，应用拟除虫菊酯杀虫剂防治咖啡潜叶虫后，南方红蜘蛛 Oligonychus ilicis 的暴发经常被报道。红螨对其主要捕食性螨虫的选择性优势通常被认为是暴发的原因，但这一理论从未得到过验证。在这里，我们评估了溴氰菊酯对两种螨虫的毒性（因此也评估了其选择性）：南方红蜘蛛及其植绥螨捕食性螨虫 Amblyseius herbicolus。此外，还使用捕食性螨虫的自由选择行为步行生物测定和两种螨虫的生命表实验，分别测试了行为回避和溴氰菊酯诱导的激素作用作为红蜘蛛暴发的潜在原因。致死毒性生物测定表明，捕食性螨虫比其猎物稍微敏感（1.5×），但在更健壮的种群生物测定中，捕食者对溴氰菊酯的耐受性是其猎物的三倍，这表明捕食者对溴氰菊酯的敏感性不是报道的暴发的原因。捕食者没有表现出对溴氰菊酯的行为回避；然而，红螨的杀虫剂诱导的激素作用导致其在低剂量下种群大量增加，而捕食性螨虫则没有观察到这种情况。因此，溴氰菊酯诱导的激素作用可能是报告的红蜘蛛暴发的原因。
