Evaluation of indigenous entomopathogenic nematodes in Southwest China as potential biocontrol agents against Spodoptera litura (Lepidoptera: Noctuidae)

Abstract

Spodoptera litura is a notorious leaf feeding insect pest in the Asia-Pacific region and leads to a significant economic loss in vegetable and field crop production. Entomopathogenic nematodes (EPNs), lethal parasites of insects, are used as biocontrol agents. Yunnan Province in China is a well-known region due to its rich biodiversity. In the present study, a survey of EPNs using the Galleria-baiting technique was conducted in 2017 and 2018 throughout the entire Yunnan province. In total, 789 soil samples were collected from 232 sites, of which 75 samples were positive for EPNs. Phylogenetic analyses of ITS, D2D3 expansion region of the 28S rRNA gene, as well as mitochondrial cytochrome c oxidase subunit I (COI), were performed to identify isolated nematode species and evaluate their genetic diversity. In total, 13, 3, and 58 identified populations belong to Steinernema, Heterorhabditis, and Oscheius, respectively. The phylogenetic relationships of EPN species in the three genera were analyzed with the Neighbor-Joining method. The virulence of the trapped isolates in the genera of Steinernema, Heterorhabditis, and Oscheius against S. litura was evaluated. Ten new indigenous isolates from Steinernema and Heterorhabditis showed prominent virulence to S. litura within 48 hr which is equivalent to that of commercial EPNs populations. The present study provides background information on indigenous EPN resources for S. litura control in Asia-Pacific region.

Identification and biocontrol potential of entomopathogenic nematodes, Steinernema siamkayai occurring in western Thailand against the common cutworm, Spodoptera litura Fabricius (Lepidoptera: Noctuidae) under laboratory and screenhouse conditions

“…Similar results were reported by Sun et al. (2021) who found that two indigenous isolates of S. siamkayai exhibited a 90% mortality in S. litura larvae after 72 h. The results also agreed with Park et al. (2001), who demonstrated that Steinernema spp.…”

“…At the same application rate, the 3rd instar larvae of S. litura were susceptible to the three indigenous EPNs both in laboratory and screenhouse conditions after 72 h of exposure. Similar results were reported by Sun et al (2021) who found that two indigenous isolates of S. siamkayai exhibited a 90% mortality in S. litura larvae after 72 h. The results also agreed with Park et al (2001), who demonstrated that Steinernema spp. were highly effective against S. litura larvae, completely killing 2nd and 3rd instar larvae within 48 h when applied at 300 IJs/larva.…”

Understanding Molecular Plant–Nematode Interactions to Develop Alternative Approaches for Nematode Control

“…Finally, the above-mentioned approaches should be integrated into PPN management in real time. For instance, there is no evidence that the novel strains of BCA have favorable traits without hard and tiring screening focusing on their virulence and versatility [130]. The alternate method is a directed search of mediums where BCAs will have had to develop the needed traits.…”

Molecular Identification and Phylogenetic Diversity of Native Entomopathogenic Nematodes, and Their Bacterial Endosymbionts, Isolated from Banana and Plantain Crops in Western Colombia

“…Therefore, it is paramount to isolate and characterize native EPNs, which may be locally adapted to the regional entomofauna. Local EPNs may be more infectious and competent in parasitism at either the adult or larval stage of development [46]. Particularly interesting are the strains that could tolerate intervened soils.…”