Field evaluation of commonly used synthetic insecticides against Thrips tabaci (Thysanoptera: Thripidae) on onion (Allium cepa) in the Central Rift Valley of Ethiopia

Abstract

Thrips are responsible for high onion yield losses and mainly controlled with the use of insecticides  There is a demand for new products against thrips due to failure of commonly used insecticides  Thus, commonly used insecticides are periodically evaluated to avoid total failure of thrips management on onion  The efficacy of nine insecticides from classes of pyrethroids, organophosphates, spinosyns, neonicotinoid and botanical were evaluated against thrips on onion using a randomized complete block design in four replications in two seasons in 2015 and 2016  The lowest thrips infestations were observed in plots treated with spinosad, spinetoram, and imidacloprid, which resulted in high marketable yield of onion both in cool and hot dry seasons  Alpha-cypermethrin, diazinon, neem anamdad cyhalothrin insecticides poorly performed on treated plots in both seasons with low marketable yields.  The performance of dimethoate and profenofos was intermediate with the intermediate yield gain over the check  Rotational application of the most effective insecticide classes of neonicotinoid and spinosyns with less effective insecticide classes of pyrethroids and organophosphates need to be practiced to safeguard their long-term efficacies and utility to thrips management  Future researches directed to the management strategy of this pest should focus on insecticide resistance management and other effective IPM options wherever the pest problem prevails.