Temperature Effects on the Development of Life Stages of Fall Armyworm, Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae) on Maize

The effect of temperature on the development of different life stages of Spodoptera frugiperda on maize was assessed at the Centre for Agro Climatic Studies, University of Agricultural Sciences, Raichur at five different constant temperatures viz., 18, 22, 26, 30, and 32°C with a constant relative humidity 65 ± 5% for all the temperatures under growth chambers conditions. Over the temperature studied, the duration of different life stages decreased with a rise in temperature from 18 to 32°C. Where, the duration of the egg stage reduced from 6.00 days (1°C) to 2.00 days (32°C); for the larva from 31.50 to 10.10 days and for the pupae from 30.86 to 6.0 days. The temperature ranges of 26 to 30°C were found to be favourable for growth and development whereas the temperature extremities of 18 and 32°C were not favourable for the growth and development of fall armyworm; at 18°C there was no eclosion and at 32°C there was eclosion of adults but mortality occurred within an hour. The linear regression studies revealed that lower developmental threshold temperatures of 11.50, 11.49, 13.90, and 20.13 and corresponding thermal constants of 43, 236, 149, and 494 degree days were recorded for the incubation period, larval period, pupal period and total life cycle respectively in order. The present study revealed that the upper threshold of 32°C and a lower threshold of 18° C were detrimental to the development of fall armyworm life stages. These estimated thermal thresholds and degree days might be used to predict the fall armyworm activity in the field for devising strategies to manage fall armyworms effectively.