Growth and development of Spodoptera frugiperda (J.E. Smith) on maize at different temperatures

In India, the invasion of Fall Army Worm (FAW), Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae), was detected as a new exotic invasive pest in May 2018 on maize from Karnataka. By August 2018, the pest had spread to the entire maize-growing areas of South India, including Maharashtra. The study aims to investigate the effects of different temperature levels viz 20 °C, 25 °C, 30 °C, and 35 °C on the growth, development, and reproductive parameters of the fall armyworm (Spodoptera frugiperda) under laboratory conditions. One of the major challenges faced during the study was maintaining consistent environmental conditions and managing high mortality rates at extreme temperatures, which affected the continuity of data collection. Despite these difficulties, the study contributes valuable insights into the thermal thresholds and biological responses of FAW under controlled settings. The larva of S. frugiperda passed through six larval instars at all temperatures and successfully completed its life cycle at varying degrees on maize, being shortest at 35 °C (18.13 ± 0.06 days) and longest at 20 °C (60.00 ± 0.07 days). The highest fecundity of S. frugiperda was registered at 30 °C (764.40 eggs per female), followed by 25 °C (696.20 eggs per female), 20 °C (451.60 eggs per female), and lowest at 35 °C (195.20 eggs per female). Highest percent pupation and adult emergence were at 30 °C (92 ± 0.60% and 98.2 ± 0.48%) and lowest at 20 °C (34 ± 0.74%) and 35 °C (68.4 ± 0.70%), respectively. Thus, the optimum temperature for the efficient growth and development of S. frugiperda was within the range of 25 to 30 °C. The findings can support targeted pest management practices and predictive modeling of FAW outbreaks in varying agro-climatic zones.