Virulence and efficacy of different entomopathogenic nematode species against western flower thrips (Frankliniella occidentalis)

Virulence and efficacy of five species and strains of the entomopathogenic nematodes of the families Steinernematidae and Heterorhabditidae: Steinernema riobravis, Steinernema feltiae strains Ger. and UK, and Heterorhabditis bacteriophora strains HP88 and IS5, against the prepupal and pupal stages of the western flower thrips (WFT), Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae), were investigated in the laboratory. Although all these nematodes controlled WFT to some extent, they differed in efficiency. The heterorhabditid nematode H. bacteriophora strain HP88 was more specific to the soil-inhabiting WFT stages (36-49% thrips mortality). The steinernematid nematodes S. riobravis and S. feltiae strains Ger. and UK had only a slight effect (10% mortality) on prepupal and pupal populations of WFT, and H. bacteriophora strain IS5 had the least effect of all. A possible reason for such species variation is suggested and discussed.