Department of Plant Protection, Faculty of Agriculture, Aydin Adnan Menderes University, Aydin, Turkey.
Department of Biology, Faculty of Arts and Science, Duzce University, Duzce, Turkey.
J Invertebr Pathol. 2021 Sep;184:107641. doi: 10.1016/j.jip.2021.107641. Epub 2021 Jun 27.
Entomopathogenic nematodes are used widely in biological insect control. Entomopathogenic nematodes can infect live insects as well as dead insects (i.e., they can act as scavengers). It is important to determine compatibility of entomopathogenic nematodes with other pest management tactics such as chemical insecticides. We hypothesized that chemical insecticides have negative impact on scavenging nematodes. According to our hypothesis, we first investigated the effects of direct exposure of Steinernema carpocapsae infectivity juveniles (IJs) to three chemical insecticides, cypermethrin, spinosad or diflubenzuron in terms of nematode survival and virulence. Subsequently, using the same chemicals, we tested the effects of insecticide-killed insects on scavenger nematode penetration efficiency, time of emergence and the number of nematode progeny. Prior to our study, the impact of pesticides on scavenger nematode fitness had not been studied. Fall webworm, Hyphantria cunea, and greater wax moth, Galleria mellonella, larvae were used as host insects. The survival rate of IJs after direct exposure was 83% for cypermethrin and 93-97% for the other insecticides and control. There were no significant differences in the survival and virulence of the nematodes after 24 h exposure to insecticides. The number of nematodes that invaded the insecticide-killed host was significantly higher in cypermethrin and spinosad treated groups and live H. cunea than in the diflubenzoron treated group and freeze-killed control. However, no significant differences were observed in time of emergence. Significantly more progeny IJs emerged from Spinosad-killed insects than the freeze-killed control. In conclusion, we discovered that the fitness of scavenging IJs is not diminished by insecticides in insect cadavers. In fact, in some cases the exposure to chemical insecticides may enhance virulence.
昆虫病原线虫被广泛应用于生物防治昆虫。昆虫病原线虫可以感染活体昆虫和死亡昆虫（即，它们可以充当清道夫）。确定昆虫病原线虫与其他害虫管理策略（如化学杀虫剂）的相容性非常重要。我们假设化学杀虫剂会对清道夫线虫产生负面影响。根据我们的假设，我们首先研究了三种化学杀虫剂（氯菊酯、多杀菌素或除虫脲）对斯氏线虫感染力幼虫（IJs）的直接暴露对线虫存活率和毒力的影响。随后，我们使用相同的化学物质测试了杀虫剂杀死的昆虫对清道夫线虫穿透效率、出现时间和线虫后代数量的影响。在我们的研究之前，还没有研究过杀虫剂对清道夫线虫适应性的影响。秋粘虫、舞毒蛾幼虫和大蜡螟幼虫被用作宿主昆虫。直接暴露后，IJs 的存活率为氯菊酯 83%，其他杀虫剂和对照为 93-97%。在接触杀虫剂 24 小时后，线虫的存活率和毒力没有显著差异。在氯菊酯和多杀菌素处理组以及活体 H. cunea 中，入侵杀虫剂杀死的宿主的线虫数量明显高于在除虫脲处理组和冷冻杀死的对照组中。然而，出现时间没有显著差异。从 Spinosad 杀死的昆虫中孵化出的子代 IJs 明显多于冷冻杀死的对照组。总之，我们发现清道夫 IJs 的适应性不会因昆虫尸体中的杀虫剂而降低。事实上，在某些情况下，接触化学杀虫剂可能会增强毒力。
