Biological control of white grubs, Holotrichia serrata (Fabricius) in sugarcane by two species of entomopathogenic fungi, Metarhizium anisopliae and Beauveria bassiana

Sugarcane is one of the important commercial crop in India and white grubs are one of the serious pests of this crop. The present study was taken up to study the efficacy of entomopathogenic fungi against Holotrichia serrata (Fabricius) in sugarcane. Laboratory bioassay studies were conducted using five strains of Metarhizium anisopliae (ICAR-NBAIR Ma-4, Ma-6, Ma-11, Ma-14a & Ma-35) and one strain of Beauveria bassiana (ICAR-NBAIR Bb-5a) on third instar grubs of H. serrata at the concentration of 1 × 108 spores/ml. M. anisopliae (ICAR-NBAIR Ma-4) strain showed 100% mortality of the grubs and the rest of the strains showed 56–80% mortality of H. serrata. Dose and time mortality studies with aqueous spore suspensions and talc formulation (2% WP) of M. anisopliae (ICAR-NBAIR Ma-4 strain) showed LC50 value of 6.67 × 104 spores/ml and 1.72 g/l andLT50 value of 122.02 h at spore dose of 1 × 108 spores/ml and 183.86 h at the dose of 5 g/l. Further field evaluation was conducted in white grub infested sugarcane during 2016–17 and 2017–18 using M. anisopliae (ICAR-NBAIR Ma-4 strain) and B. bassiana (ICAR-NBAIR Bb-5a) for management of white grubs, H. serrata in Karnataka state of India. The results showed soil applications of 250 kg of M. anisopliae, (ICAR-NBAIR Ma-4) enriched Farmyard manure per hectare two times (June & July) effectively reduced the grub population of H. serrata by 86–89% leading to reduced plant damage and increased yield (33–34%). This treatment was better than the insecticidal application in the management of sugarcane white grubs.