Management of the grape mealy bug, Maconellicoccus hirsutus (Green), using entomopathogenic fungi and botanical oils: a laboratory study

Abstract

Background: Laboratory experiments were conducted to evaluate the bio-efficacy and cumulative effect of entomopathogenic fungi (EPF), viz., Lecanicillium lecanii (Zimmermann) Zare and Gams, and Beauveria bassiana (Balsamo) Vuillemin and different botanical oils against grape mealy bug, Maconellicoccus hirsutus (Green). M. hirsutus infestation during berry formation has left no option other than chemical management. However, the pesticide application during this stage leads to residues. Thus, safer and sustainable biological need was tested for their effectiveness against M. hirsutus. Results: Dipping bioassay technique was used to determine the cumulative mortality. When L. lecanii was used as sole (at 6 and 4 g/l), significant mortality was observed (51.63 and 50.18%). However, the maximum cumulative nymphal mortality was achieved when the combination of EPF formulations was used, i.e., 57.64% with B. bassiana + L. lecanii (6 g/l + 6 g/l). Their effectiveness was at par with the same combination but with minimal concentration, i.e., 4 g/l + 4 g/l (56.29%). Concerning the botanical oils evaluated, neem oil at 15 ml/l achieved a higher mortality of 81.36%. Consecutive effective treatment was a combination of neem oil and pongamia oil (at 10 + 10 ml/l) with 79.65% mortality. However, the standard dosage of neem oil (at 10 ml/l) and IIHR neem soap (at 10 g/l) also recorded the significant mortality of 78.09 and 77.67%, respectively. When compared, the neem oil was found significantly superior in sole and compatible combination than pongamia oil. Conclusions: Lecanicillium lecanii and neem oil (sole and in combination with other compatible bioagents) proved significantly better for the management against M. hirsutus with an efficacy of 90.21 and 96.67 % mortality, respectively against the standard chemical control (more than 97%).