Biology and biometric characteristics of Spodoptera frugiperda (Lepidoptera: Noctuidae) reared on different host plants with regard to diet.

Background: The fall armyworm (FAW) Spodoptera frugiperda (J. E. Smith), native to the Americas, is a new invasive pest that was reported in India for the first time in May 2018. Being polyphagous, FAW can infest several different hosts and increase its population all year round. In this context, the present study was conducted under laboratory conditions to evaluate the biological parameters of FAW on four different hosts, Zea mays (maize), Gossypium hirsutum (cotton), Ricinus communis (castor) and Brassica oleracea var. botrytis (cauliflower), and a semi-synthetic diet.

Results: The shortest life cycle of 32.8 ± 0.52 days in males and 34.1 ± 0.43 days in females was observed on maize. Semi-synthetic diet was superior in terms of higher mean fecundity (1324.6 ± 61.21 eggs), larval weight (503 ± 0.02 mg), pupal weight (263 ± 0.01 mg) and adult female weight (128 ± 0.0 mg) compared with natural hosts. Cotton was the least preferred host with a longer life cycle of 49.5 ± 0.50 days. Head capsule width and length were measured and the growth rate was validated using Dyar's rule. The mean width and length of the head capsule of first-instar larvae of FAW on different hosts was 0.35 ± 0.00 mm. The maximum width (2.76 ± 0.03 mm) and length (2.31 ± 0.03 mm) were observed in sixth-instar larvae grown on diet.

Conclusion: The results of this study will be instrumental in understanding and formulating management strategies for FAW.