Insecticide application schedules for fall armyworm Spodoptera frugiperda (Lepidoptera: Noctuidae) control and their partial budget impact on irrigated maize in the Raya Valley District, Tigray, Ethiopia

Focusing on the fall armyworm Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae), a significant economic pest in Ethiopian maize capable of causing 50% field damage, this research aimed to determine the best application schedule for the insecticide Tutan 36%SC Plus in the Raya Valley District. The study documented significant differences in fall armyworm incidence and damage to maize leavesand cobs among the various treatment schedules. Treatments with more frequent applications (T10, T9, T8, T7) achieved superior pestcontrol, evidenced by the lowest incidence and damage levels. In contrast, the highest pest incidence and damage occurred in the untreated control (T1) and treatments with fewer or poorly timed applications (T3, T2, T4, T5). This pattern is held for leaf injury, cobdamage, and larval presence. Maize yield also varied significantly, ranging from 12.13 to 49.03 quintals per hectare. Maximum yields were associated with frequent applications (T10, T9, T8, T7), while minimum yields were recorded for the untreated control (T1) and plotswith infrequent or suboptimal sprays (T2, T3, T4 and T5). Partial budgeting analysis indicated that the schedule of three bi-weekly applications (T7) was the most economically viable, yielding the highest Marginal Rate of Return (MRR) at 3916.865% and a mean grain yield of 44 qt/ha. The researchers conclude that this T7 schedule should be scaled up and demonstrated in the Rata Valley district andextended to other areas with similar agro-ecological conditions.