Efficacy of indigenous isolates of entomopathogenic fungi, Beauveria bassiana against the box tree moth, Cydalima perspectalis, invasive pest in Iranian forests

Cydalima perspectalis (Walker), box tree moth (BTM) is a major invasive pest of Buxus hyrcana Pojark in northern Iran that has spread across Asia and Europe. To reduce the use of insecticides in the management of forest pests, developing integrated pest management (IPM) programs using biocontrol agents can be an effective strategy. During our studies on native entomopathogenic fungi (EPF) in northern Iran, Beauveria bassiana (B2, F4, D2, B1) were naturally isolated from BTM larvae in Hyrcanian forests. Under laboratory conditions, the potential of the naturally occurring EPFs as a biological control method against the third-instar larvae of BTM was evaluated. The mean lethal concentration values (LC50) of isolates B2, F4, D2 and B1 were found to be 1.2×107 , 2.0×107 , 2.8×107 and 1.0×108 conidia ml−1 , respectively on third-instar BTM larvae in the laboratory tests 96 hours after the treatment at 26 ± 1 °C, 75 ± 5% relative humidity. Under field conditions, the foliar applications of isolate B2 formulations containing linseed oil, corn oil, soybean oil, and wettable powder resulted in 13.2-82.2% mortality against BTM in Maskupa, Mazandaran and 8.8-70.4% mortality in Sisangan Forest Park, Mazandaran (after 14 days at a concentration of 108 conidia ml−1 ), respectively. This investigation suggests that BTM larvae in Hyrcanian forests contain pathogenic B. bassiana isolates and highlights for the first time their potential as a biological control agent against BTM.