Effect of Storage Duration on the Insecticidal Activity of Neem (<i>Azadirachta indica</i>) Seeds Against Fall Armyworm (<i>Spodoptera frugiperda</i>)

Abstract

Neem (<i>Azadirachta indica</i>), native to India, thrives in tropical and sub-tropical climates. Its efficacy against economically significant pests is attributed to the pesticidal properties found in its leaves, bark, and roots. Neem seeds are always harvested by smallholder farmers and stored for use in crop-growing seasons when their availability is scarce. This study aimed to determine if storage duration can affect the toxicity of these neem seeds. Neem seed extracts were tested for toxicity after being stored at different durations, they were stored for 1-3 years. The objective of this study was to analyze the effects of storage time on the insecticidal activity of neem seeds. Fall armyworm larvae were used to test for the neem seed extracts’ toxicity by feeding on maize plants which were sprayed with these extracts. The experimental design used was a complete randomized design in the laboratory. Extracts were made from neem seeds stored for 1-3 years which were harvested from year 2019, 2020, 2021 and 2022. Analysis of FAW larvae mortality at different concentrations (0.5%, 1.0%, 1.5%, and 2.0%) together with the control treatment under laboratory conditions was done. Damage severity rates of maize leaves in which the FAW larvae were allowed to feed were measured and FAW larvae mortality was calculated. The results showed a significant interaction between neem seed storage time and FAW mortality. The results showed that extracts from fresh neem seeds and those stored for one year had the lowest plant damage score. Also, the lowest mortality was obtained from seeds stored for 1 year and the fresh seeds because the larvae refrained from feeding. Following this study, we recommend the usage of fresh neem seeds and those stored for up to a year in the management of fall armyworms.