Temperature-dependent Life History Traits of Fall Armyworm, Spodoptera frugiperda

A mid-May 2018 outbreak of fall armyworm (FAW) was witnessed in Karnataka and it then spread rapidly across the country, causing extensive damage to maize crop. It is ideally adapted to tropical and subtropical environments around the world. Temperature has a major role in synchronizing its invasion and life cycle since it does not go into diapause.

An investigation was conducted, to examine the life-history parameters of fall armyworm (FAW), Spodoptera frugiperda Smith fed with maize foliage at five different temperatures viz.,18, 20, 25, 30, 35 and 40±1°C, under 14 hr light and 10 hr dark cycle maintained inside a BOD incubator.

Results revealed an inverse relation between developmental stages of eggs, larvae and pupae and growing temperatures, wherein the fastest growth occurred at 35°C and no development was observed at 40°C. Maximum percentage hatchability was noticed at 25°C (94.2%), while it decreased both at higher and lower temperatures. The larval developmental duration decreased from 34.08 days at 18°C to 10.06 days at 35°C. The duration of pupal development was also minimum at 35°C, taking 7.22 days. Adult longevity decreased linearly with an increase in temperature where females outlived males at all temperatures except at 18°C. The thermal constants for development were estimated at 45.92 (egg), 245.34 (larvae), 169.64 (pupae) and 466.06 degree days (total).