Relative Susceptibility of Cashew Stem and Root Borers (CSRB), Plocaederus Spp. and Batocera rufomaculata (De Geer) (Coleoptera: Cerambycidae) to Entomopathogenic Nematodes

Cashew stem and ischolar_main borers (CSRB) viz., Plocaederus ferrugenius L., Plocaederus obesus Gahan and Batocera rufomaculata De Geer are major pests of cashew (Anacardium occidentale L.) in all cashew growing tracts of India. The grubs of these CSRB species damage the vascular tissues by internal tunneling, thereby gradually killing the infested trees leading to decline in tree density. Studies were conducted at Directorate of Cashew Research, Puttur during 2010-11 to evaluate the effectiveness of entomopathogenic nematodes (EPN), Heterorhabditis indica Poinar (Rhabditida : Heterorhabditidae), Steinernema abbasi Elawad (Rhabditida : Steinernematidae) and Steinernema bicornutum Tallosi (Rhabditida : Steinernematidae) against the grubs of Plocaederus spp. and B. rufomaculata. All the three species of EPN induced mortality of Plocaederus spp. grubs in a mean duration of 14.11, 12.88 and 12.37 days respectively. The younger grubs (<45 days) of Plocaederus spp. showed equal susceptibility to all the three speices of EPN. In case of grubs of B. rufomaculata, H. indica induced mortality within a mean duration of 7.43 days, which was superior than mortality induced by S. abbasi (18.25 days) and by S. bicornutum (17.94 days). It was noticed that the body weight was strongly correlated to emergence of IJs in all the three spp. of EPN. Studies on survival of the infective juveniles (IJs) in soil and persistence of virulence indicated that all the three species of EPN could survive in soil upto 150 days.