Kalia Vinay, Sharma Garima, Shapiro-Ilan David I, Ganguly Sudershan
Division of Entomology, Indian Agricultural Research Institute, New Delhi 110012, India.
USDA-ARS, Southeastern Fruit and Tree Nut Research Laboratory, 21 Dunbar Road, Byron, GA 31008.
J Nematol. 2014 Mar;46(1):18-26.
Under laboratory conditions, the biocontrol potential of Steinernema thermophilum was tested against eggs and larval stages of two important lepidopteran insect pests, Helicoverpa armigera and Spodoptera litura (polyphagous pests), as well as Galleria mellonella (used as a model host). In terms of host susceptibility of lepidopteran larvae to S. thermophilum, based on the LC50 36 hr after treatment, G. mellonella (LC50 = 16.28 IJ/larva) was found to be more susceptible than S. litura (LC50 = 85 IJ/larva), whereas neither host was found to be significantly different from H. armigera (LC50 = 54.68 IJ/larva). In addition to virulence to the larval stages, ovicidal activity up to 84% was observed at 200 IJ/50 and 100 eggs of H. armigera and S. litura, respectively. To our knowledge this is the first report of entomopathogenic nematode pathogenicity to lepidopteran eggs. Production of infective juvenile (IJ) nematodes/insect larva was also measured and found to be positively correlated with rate of IJ for H. armigera (r = 0.990), S. litura (r = 0.892), as well as G. mellonella (r = 0.834). Both Phase I and Phase II of symbiotic bacteria Xenorhabdus indica were tested separately against neonates of H. armigera and S. litura by feeding assays and found to be virulent to the target pests; phase variation did not affect the level of virulence. Thus S. thermophilum as well as the nematode's symbiotic bacteria applied separately have the potential to be developed as biocontrol agents for key lepidopteran pests.
在实验室条件下，对嗜热斯氏线虫针对两种重要鳞翅目害虫棉铃虫和斜纹夜蛾（多食性害虫）以及大蜡螟（用作模式宿主）的卵和幼虫阶段的生物防治潜力进行了测试。就鳞翅目幼虫对嗜热斯氏线虫的宿主易感性而言，根据处理后36小时的半数致死浓度（LC50），发现大蜡螟（LC50 = 16.28 感染性幼虫/幼虫）比斜纹夜蛾（LC50 = 85 感染性幼虫/幼虫）更易感，而这两种宿主与棉铃虫（LC50 = 54.68 感染性幼虫/幼虫）相比均无显著差异。除了对幼虫阶段具有毒力外，在200 感染性幼虫/50枚棉铃虫卵和100 感染性幼虫/50枚斜纹夜蛾卵时，分别观察到高达84%的杀卵活性。据我们所知，这是昆虫病原线虫对鳞翅目卵致病性的首次报道。还测量了感染性幼虫线虫/昆虫幼虫的产量，发现其与棉铃虫（r = 0.990）、斜纹夜蛾（r = 0.892）以及大蜡螟（r = 0.834）的感染性幼虫率呈正相关。分别通过喂食试验对共生细菌印度致病杆菌的I期和II期进行了测试，发现它们对目标害虫具有毒力；相变不影响毒力水平。因此，嗜热斯氏线虫以及单独应用的线虫共生细菌有潜力被开发为关键鳞翅目害虫的生物防治剂。
