Virulence of Entomopathogenic Nematodes to Pupae of Frankliniella fusca (Thysanoptera: Thripidae)

Abstract

Tobacco thrips, Frankliniella fusca (Hinds) is an economically significant pest. Entomopathogenic nematodes (EPNs) have shown promise as biocontrol agents against certain thrips species, but they have not been explored for suppression of F. fusca. We investigated the potential of EPNs to manage F. fusca by conducting three different bioassays: 1) a small cup dose-response bioassay (25, 50, and 100 IJs cm-2) with four EPN species, 2) a broad virulence bioassay with eight EPN species at 100 IJs cm-2, and 3) a potted soil bioassay testing with four EPN species (100 IJs cm-2). In the dose-response bioassay, all treatments showed relatively lower adult emergence when compared with the control group, but the minimum adult emergence (30%) was observed at 7 d post-treatment when Heterorhabditis bacteriophora (FL1-1) was applied at the highest rate (100 IJs cm-2). In the broad virulence study, all EPN treatments caused significant reductions in F. fusca adult emergence (18.3-75.0%) in comparison with the control. H. bacteriophora (Fl1-1) was more virulent than other nematode treatments but statistically not different from Steinernema feltiae and Steinernema riobrave, while Steinernema rarum was the least virulent. In the potted soil bioassay, the lowest emergence (10.6%) was observed in H. bacteriophora (Fl1-1) treatment, followed by S. feltiae (SN), S. riobrave (355), and Heterorhabditis indica (HOM1) treatments. These results indicate that EPNs have the ability to suppress the soil dwelling stage of F. fusca and should be explored further under greenhouse and field conditions for biocontrol potential within an integrated pest management (IPM) context.