Life table studies of sugarcane scale, Melanaspis glomerata G.*

Life table studies of Melanaspis glomerata conducted in vitro on CoC 671 (susceptible) and CoSi 86071 (resistant) genotypes under limiting and non-limiting environment at Sugarcane Research Station Sirugamani revealed that the innate capacity for increase in numbers, finite rate of natural increase and weekly multiplication of the population was high in CoC 671. The value of cohort generation time and mean generation time increased in CoSi 86071 while the innate capacity for increase came down. Life table studies under field conditions indicated that the dispersal of crawlers and mortality due to unknown causes in the early instars were the key mortality factors. Mortality due to predators and parasites was low. Parasitisation was evident only in the fourth instar and fifth instar by Adelencyrtus mayurai Subba Rao and Botryoideclava bharathiya Subba Rao. Lower values of trend index were recorded in CoSi 86071 when compared to CoC 671. Maximum contribution to generation mortality was from the first two instars and total generation mortality was higher in CoSi 86071 (K = 1.7034) when compared to CoC 671 (K = 1.6134).