Ovicidal and insecticidal effects of microbial pathogens against invasive Coconut Rugose spiralling whitefly (RSW), Aleurodicus rugioperculatus Martin and impact on their chrysopid predator Mallada boninensis (Okamoto)

Abstract Background The Rugose spiraling whitefly (RSW), Aleurodicus rugioperculatus Martin (Hemiptera: Aleyrodidae), has been reported as an invasive pest of coconut in different parts of peninsular India during 2016. It mainly caused damage to coconut palms, bananas, custard apples and other broad-leaved plants as hosts. Presently it is spread all over India and the coconut growing farmers are facing hard ships due to this infestation of RSW in coconut ecosystem. Still now the management of this invasive pest is fully based on the biological control, particularly with predators and parasitoids and the study on the microbial control of RSW was minimum. Hence, an attempt was made to study the ovicidal and insecticidal effects of microbial pathogens, viz. Isaria fumosorosea Wize, Beauveria bassiana (Balsamo) Vuillemi, Metarhizium anisopliae (Metschnikoff), Lecanicillium lecanii (Zimmerm.) with a spore load of 1 × 108 cfu against different life stages of RSW and their chrysopid predator, Mallada boninensis (Okamoto)(Neuroptera: Chrysopidae) under laboratory as well as field conditions. Results The results revealed that under laboratory conditions, I. fumosorosea caused 34.54% egg mortality, 37.39% nymphal mortality and 48.30% adult mortality, followed by L. lecanii (24.54, 30.76 and 28.01%) and M. anisopliae (20.56, 32.51 and 42.92%) for egg, nymphal and adult mortality, respectively. Under field conditions, I. fumosorosea caused (29.60%), followed by M. anisopliae (24.30%) and B. bassiana (21.00%) nymphal mortality, respectively, at 15 days after spray, also, it was found effective in reducing the RSW population on coconut. The impact of fungal entomopathogens against the predator revealed that I. fumosorosea treated eggs of M. boninensis recorded maximum 90.33% grub emergence than other treatments. Conclusion The present study concludes that the RSW can be controlled effectively by I. fumosorosea along with the chrysopid predator, M. boninensis under field conditions as they showed maximum ovicidal and insecticidal actions against different life stages of RSW and safer to the major predator of RSW and fall under harmless category as per the classification of IOBC.