Biology and host preference studies of Spodoptera frugiperda (Smith) (Lepidoptera: Noctuidae) in Ethiopia

Abstract

The fall armyworm (FAW), Spodoptera frugiperda, was first reported on the African continent in early 2016 and reported from Ethiopia in early 2017. The host preference and its biology are not known in Ethiopia. Therefore, the current study was aimed at studying the biology and host preferences of FAW. The experiment was carried out in the greenhouse and wire-house of Ambo Agricultural Research Center from July 2021 to October 2021. The biology of FAW was studied using maize, sorghum, chickpeas, barley, and wheat. The experiments were conducted in the average rearing room temperature of 25.5°C to 37.4°C and relative humidity of 35.33% to 45.46%. Data on egg incubation period, pre-pupal, pupal, egg to adult period, pupal weight, sex ratio, and cannibalism percentage were collected for the biology study. The egg incubation period was between 5 and 8 days. The larval developmental period completed in 14 to 19 days, while pupal stage needed 8 to 9 days. FAW females lay 32-122 eggs in their lifetime. The oviposition period was 2 to 3 days. FAW life cycle ranged from 31 to 38 days at the specified temperature and relative humidity. In terms of the sex ratio of FAW, there was no difference between the tested crops. However, significant (P<0.05) variation was observed with respect to larval cannibalism when reared on different crops. The host preference study was carried out using choice and no-choice experiments on 23 different crops. Data on preferences for oviposition by adult females and for larval feeding were collected. Compared to the other studied host crops, it was discovered that maize, sorghum, swiss chard, teff, elephant grass, and cabbage were the most preferred hosts for larval development and egg laying. The adult female laid eggs on faba bean, soya bean, haricot bean, garlic, and mustard plants, but the eggs did not hatch into larvae. These findings have important implications for understanding the FAW survival, development, and host preference, as well as knowing the best time to plan its effective management.