Efficacy of Entomopathogenic Nematodes Against the Tobacco Cutworm, Spodoptera litura (Lepidoptera: Noctuidae)

Abstract

Spodoptera litura (F.) is an obnoxious cosmopolitan pest that causes serious damage to different economic crops. Entomopathogenic nematodes (EPN) have the potential to control the S. litura larvae. Fifteen EPN isolates were screened, and Steinernema sp. 64-2, four isolates of S. carpocapsae (Weiser), S. longicaudum (Shen & Wang) X-7, and two isolates of H. indica (Poinar, Karunaka & David) were found to cause higher mortality of the second, third, and fourth instars of S. litura than the other tested isolates, with larval mortality rates > 90% after 48 h of exposure. An exposure rate of 12.5 infective juveniles per larva was enough for S. carpocapsae A24, All, and G-R3a-2 and S. longicaudum X-7 to cause 100% mortality of the second instar, and for S. longicaudum X-7 and H. indica 212-2 to cause 100% mortality of the third instar. Five EPN isolates were tested on their virulence at different temperatures and found that all the five EPN isolates performed well against the S. litura larvae at 25 and 30°C, but were not active at 10 and 15°C. Two S. carpocapsae isolates (All and Mex) were virulent against the S. litura larvae at lower temperatures. The five tested EPN isolates were also found to have the ability to infect and kill the pupae of S. litura in the laboratory. The present study further proves that EPN are effective at controlling S. litura, which may partially substitute the use of chemical insecticides, thus reduce the overuse of chemical insecticides.

Additive interactions of some reduced-risk biocides and two entomopathogenic nematodes suggest implications for integrated control of Spodoptera litura (Lepidoptera: Noctuidae)

“…Many insect pests including armyworms, Spodoptera spp., have been reported to develop resistance against the insecticides used in pest management programs 1,2,8 . Combining certain efficient techniques like biological control agents, especially EPNs, and insecticides can help address the challenges in management of certain pest insects in agriculture 7,12,13,21,25,35,36 .…”

Virulence of Steinernema ceratophorum against different pest insects and their potential for in vivo and in vitro culture

“…In the present study, S. ceratophorum were also found to be effective against different instar larvae of S. exigua, O. ubilalis, H. armigera and young larvae of S. frugiperda when applied at 50-200 IJ/larva in the laboratory, when compared to the published EPN isolates. Steinernema ceratophorum was first reported and identified in north-east China (Jian et al, 1997) and later isolated in north and south-west China (Ma et al, 2010;Yan et al, 2020). Steinernema ceratophorum caused high mortality of larvae of the bark beetle Dendroctonus valens LeConte (Coleoptera: Scolytidae) (Jian et al, 2002), Haemaphysalis longicornis Neumann (Acari: Haemaphysalinae) (Gao et al, 2004) and Bradysia odoriphaga Yang & Zhang (Diptera: Sciaridae) (Ma et al, 2013a, b).…”

“…In previous research to screen EPN species/isolate against the tobacco cutworm, Spodoptera litura L. (Lepidoptera: Noctuidae), an isolate recovered from the Yunnan survey, Steinernema sp. 64-2, was found to be with high virulence against S. litura (Yan et al, 2020). This indigenous EPN isolates may contribute to successful pest control in the tobacco field in Yunnan.…”

“…For the 2nd and 3rd instar of H. armigera and S. exigua, and different larval stages of O. nubilalis, 9-cm-diam. Petri dishes were used for bioassays (Yan et al, 2020). Briefly, 10 larvae were added in each Petri dish, lined with two layers of 9-cm-diam.…”

“…To collect EPN sources for better control of the tobacco (Nicotiana rustica L.) pests, an extensive survey of EPN was conducted in the tobacco planting area in Yunnan province, China. Several EPN isolates were collected and maintained in the laboratory (Yan et al, 2020). In previous research to screen EPN species/isolate against the tobacco cutworm, Spodoptera litura L. (Lepidoptera: Noctuidae), an isolate recovered from the Yunnan survey, Steinernema sp.…”