Potential of different entomopathogenic nematode strains in controlling Atrijuglans hetaohei Yang (Lepidoptera: Heliodinidae).

Background: Atrijuglans hetaohei (Yang) (Lepidoptera, Heliodinidae) is a major pest of walnut in China. Larvae feed on the seeds of walnut fruit. Damaged fruits turned black and fallen prematurely. Current management relies upon broad-spectrum of chemical insecticides applied in the late spring or early summer. However, due to missed applications or poor application timing, high levels of A. hetaohei infestation may still occur. Entomopathogenic nematodes (EPNs) have been long used for suppressing the soil-dwelling and fruit-boring pest, but few were done on the control of A. hetaohei. The present study was conducted to determine the virulence of seven EPN strains against A. hetaohei under laboratory conditions. Results: Among the seven EPN strains, Steinernema glaseri (Sgib strain) (Rhabditida: Steinernematidae) had good potentials in the management of A. hetaohei because of the better desiccation tolerance and pathogenicity than other strains. The cocooned and mature larvae of A. hetaohei all could be infected by the nematodes of Sgib strain. Sgib strain had the best efficiency to A. hetaohei under the infection condition of 24 °C and 100 IJs per larva. At 48-h exposure to 24 °C, the highest mortality rate of A. hetaohei treated with Sgib strain was 96.67%. Sgib strain of 100 IJs/larva caused 100% mortality after 72-h post-application. Conclusion: Sgib strain from Steinernematidae was the favorable to control A. hetaohei larvae which inhabit in the soil surface effectively. Sgib strain may be a contribution to the biological control of A. hetaohei in China. Highlights: Steinernema glaseri (Sgib strain) could be used as biocontrol agent for A. hetaohei larvae because of the better anti-desiccation ability and pathogenicity. Sgib strain showed high infectivity to the cocooned larvae as well as the mature larval A. hetaohei. Sgib strain had the optimum infecting effect with 100 IJs per larva at 24 ℃ and still maintained high pathogenicity after spraying into the field for 96 h. The results suggested that some potential for Sgib strain from Steinernematidae as one tool in controlling A.hetaohei larvae, which is the main fruit-boring pest of walnut in China [ABSTRACT FROM AUTHOR]