Farmers insecticide use practices and species composition and abundance of thrips species (Thysanoptera: Thripidae) on onion in the Rift Valley of Ethiopia

A survey was conducted in 2016 in the major onion producing areas of the Ethiopian Central Rift Valley. A structured questionnaire was used to assess farmers’ management practices with a focus on the use of insecticides. Plant samples were collected to assess species composition of thrips and their abundance. Results showed that insecticides were the only control methods for onion growers to control thrips infesting onion. The insecticides diazinon, dimethoate, profenofos, lambda-cyhalothrin and spinetoram were commonly used. Level of insecticide use was higher in Meki than Melkassa and Werer. The volume of insecticide for thrips control and thrips population was noted to be on the increase over the years. Frankliniella occidentalis and Thrips tabaci were present in all surveyed areas with T. tabaci accounting for a higher proportion. The relative species composition varied significantly with location. The highest proportion of T. tabaci was recorded at Werer, where insecticide use was relatively minimal. On the other hand, F. occidentalis was highest at Meki where insecticide use was also higher. The study suggests that thrips infesting onion have developed resistance to the commonly used insecticides. Further studies are required to confirm and develop a thrips resistance management program in the area. Key words: Frankliniella occidentalis, Thrips tabaci, onion, species composition.