First report on the comparative biology of white grub, <i>Holotrichia serrata</i> (Coleoptera: Scarabaeidae) in sugarcane and artificial diet and its implications in pest management

Abstract White grub, Holotrichia serrata (Coleoptera: Scarabaeidae), is one of the most destructive pests of sugarcane in India. Though it is a major pest, its biology in sugarcane has not yet been studied in detail. It would be difficult to manage the pest without knowing its biology on the host plant. Hence, the biology of H. serrata was studied in sugarcane and its shoot powder‐based artificial diet under laboratory conditions. This is the first report on the biology of H. serrata in sugarcane and artificial diet. The artificial diet standardised in this study could support the pest to complete its life cycle successfully. In sugarcane shoot chips, the duration of egg, larval and pupal stages of male individuals was 10–12, 121–154 and 15–21 days, respectively. The corresponding values for females were 10–12, 120–151, and 15–20 days, respectively. The longevity of adult males and females was in the range of 57–78 and 68–81 days, respectively. Male and female insects completed their life cycle in 237.1 and 240.5 days, respectively. In artificial diet, they could complete their life cycle in 255.4 and 275.3 days, respectively. Sugarcane chips and the artificial diet have thus been proved to support the entire life cycle of H. serrata . In the present study, H. serrata passed through three instars to attain its pupal stage both in natural host and artificial diet. The mean head‐capsule widths were 2.72 + 0.09, 4.49 + 0.15 and 7.25 + 0.59 mm for the first through third instar grubs of cane‐reared population. The corresponding values for diet‐reared grubs were 2.74 + 0.20, 4.66 + 0.37 and 7.66 + 0.25 mm, respectively. The mean Dyar's ratios were 1.633 and 1.672 for cane‐reared and diet‐reared grubs, respectively. Excellent linearity between the instars and mean head‐capsule width, and frequency histogram with three prominent peaks confirm that the white grub has three instars. The findings of this study would have a significant impact in applied entomology. The use of sugarcane shoot chips or an artificial diet to rear the population under laboratory conditions is simple, cost‐effective and ensures the availability of grubs all through the years for the studies on applied agricultural entomology.