Monitoring of the Seasonal Occurrence of Fall Armyworm Populations in Zea mays L. in Nagaland

Abstract

Background: Maize is the second most important crop next to rice, and is grown in all the districts of Nagaland. It is affected by many abiotic and biotic stresses. Among those constraints, insect pests are the most limiting factor in the successful cultivation of maize starting from germination to harvesting. Aim: The study aimed to correlate leaf infestation percentage and the number of larvae infested with the weather parameters in maize. Methodology: A Randomized Block Design was adopted. The study was conducted at the Department of Entomology, SAS, Nagaland University, Medziphema campus, Nagaland, from May to September during 2022 and 2023. Maize variety BIO-9637 Maharaja was used to observe the incidence of the pest. The readings were taken in a zig-zag pattern, in the form of a “W” pattern in the field. The population per plant were expressed as the mean of three replications. Each replication of data was the mean of data obtained from 10 plants. The data obtained were subjected to ANOVA. Larval count and per cent leaf damage were recorded once a week during the crop period. Results: The incidence of fall armyworm (FAW) infestation was first recorded in 24th SMW at 1.22 larvae/10 plants during 2022 and 1.32 larvae/10 plants during 2023. Initial leaf damage was recorded at 5.32% during 2022 and 5.78% during 2023. The infestation increased steadily, reaching its peak at 83.86% on 28th SMW (2022) and 80.25% on 27th SMW (2023). Correlation analysis revealed that in both years, leaf damage and larval incidence were positively and significantly associated with maximum (r=0.759* and 0.850* respectively) and minimum temperatures (r=0.664* and 0.832* respectively), while relative humidity exerted a negative influence. Rainfall showed little effect. Conclusion: FAW incidence in maize is strongly temperature-dependent, with humidity exerting a significant negative effect, and rainfall having minimal influence. Management strategies should be proactive during periods of high temperature and low humidity, with interventions timed within the short window between pest establishment and peak damage.