Fall Armyworm, Spodoptera frugiperda (J.E. Smith) Damage Severity on Maize Crops in Farmers’ Field Conditions in Kathmandu Valley

Abstract

Maize, a major staple crop that is essential for Nepal's food security and rural livelihoods, is increasingly threatened by the invasive fall armyworm (Spodoptera frugiperda J.E. Smith), which causes substantial yield losses while farmers' heavy reliance on indiscriminate pesticide use and limited knowledge of sustainable management practices obstruct effective control. Field survey was carried out in six major maize-growing areas of Kathmandu valley- Kathmandu, Bhaktapur and Lalitpur districts to assess the fall armyworm, Spodoptera frugiperda (J.E. Smith) incidence, severity and farmers’ management practices during maize growing season in 2024. Semi-structured questionnaires were used for farmer interview , and damage assessment in the field was recorded using a score ranging from 1 to 9 scale based on the reference damage on the scaling of the leaf lesions, scraping of leaf surfaces and visual observations of the damage symptoms. Data analysis and result interpretation were carried out using MS Excel 2016 and SPSS version 29.0.2.0. Results indicated that maize crop damage incidence and severity varied significantly (p<0.05) with p<0.001 at vegetative and p=0.005 reproductive stages. Damage severity was highest in V11 stage during vegetative stage and dough (R4) stage during reproductive stage of maize crop. Similarly, in relation to temperature, the damage was more at temperature range of 25°C to 27°C. The highest infestation (91%) was observed in Kathmandu compared to other two districts. The survey indicates that maize farmers have to focus on agro-ecological adoption approaches like chemical, cultural, physical/mechanical, IPM, biological, and botanical measures for the management of this pest.