Effect of Integrating Maize Varieties and Insecticides against Fall Armyworm (Spodoptera frugiperda, J.E. Smith) (Lepidoptera: Noctuidae) in Central Tigray, Ethiopia

Abstract

Fall armyworm (Spodoptera frugiperda) is the most devastating insect causing economic losses of maize production and productivity particularly in tropical and subtropical. A field experiment was conducted in 2024 under irrigated conditions to determine the integrated effect of insecticides with maize varieties against naturally occurring fall armyworm infestations. A randomized complete block design with two factors and three replications was used. The first factor included two improved maize varieties (Melkassa-2 and Melkassa-4), and one local variety (Berihu) while the second factor comprised four synthetic insecticides (Chlorfenapyr + Spinosad, Chlorfenapyr, Acetamiprid + Abamectin, Imidacloprid) and one control (water spraying) spraying three times. Data collected includes fall armyworm (FAW) larvae and egg masses count, plant damage, yield, and yield-related attributes analyzed with the Genstat software version 18. The result revealed that all the treatments significantly (p < 0.05) affected the FAW population, plant damage, and grain yield compared to the control. The highest larvae mortality (94.74%), lowest leaf incidence (4%), lowest leaf severity (0.993), lowest ear damage(1.667), highest ear length (23.23 cm), highest grain yield (5166 kg ha-1), highest avoidable yield loss (42.35%), and highest Marginal return rate (39071.6%) were obtained from Melkassa -2 treated with Spinosad +Chlorfenapyr, while the untreated Berihu variety showed the lowest larvae mortality (-44.55%), lowest egg masses (1.778), highest leaf incidence (98%), highest leaf severity (8.067), highest ear damage (8.133), shortest ear length (8.9cm) and lowest grain yield (1935 kg ha-1). Furthermore, Melkassa-2 showed the lowest leaf incidence, leaf, tassel, and ear severity, highest larval mortality, highest grain yield, and highest yield loss in comparison to the tested varieties. The minimum days required for tasselling (61.5), silking (65), maturity (99.2), highest plant height (186.4), and egg masses (3.889) were recorded from Spinosad +chlofenapyr insecticide. In conclusion, the highest FAW larvae mortality rate, lowest plant damage, uppermost MRR, lowest yield loss, and grain yield were found when the Melkassa-2 variety was treated with Spinosad+ Chlorfenapyr followed by Chlorfenapyr alone. Thus, it can be recommended that farmers use the integration of the tolerant maize (Melkassa-2) variety with selective insecticides (Spinosad+chlorfenapyr) to reduce the fall armyworm damage thereby enhancing maize productivity.