Evaluation of botanicals for onion thrips, Thrips tabaci Lindeman, (Thysanoptera: Thripidae) control at Gum Selassa, South Tigray, Ethiopia

Abstract

Field studies were conducted for two consecutive years (2013 and 2014) to determine the effectiveness of different plant extracts and synthetic chemical insecticides for the control of onion thrips (Thrips tabaci) at Adigudom, Southern Tigray, Ethiopia. Two chemical insecticides including dimethoate 40% E.C and Lambda-cyhalothrin (Karate 5 EC), and five botanical extracts obtained from neem (Azadirachta indica A. Juss), Mexican marigold (Tagetus minuta L.), tree tobacco (Nicotiana glauca Graham) and Jimson weed (Datura stramonium L.) were tested for their controlling effect on onion thrips. The population dynamics of the thrips was monitored and population counts were made before and after the application of each of the treatments. The two years combined analysis indicated that there was a significant difference (p<0.05) in onion bulb yield where dimethoate, Tree tobacco, Karate, and Mexican marigold recorded significantly higher onion bulb yield than the control. Thirty and 37% more bulb yield was obtained in the Tree tobacco and dimethoate treated plots than in the control. Karate has had the highest effect in reducing thrips pest population in year one, though was on par with that of dimethoate, did well in the second year contributing to significant yield improvement against the control. There was no statistically significant difference among treatments in plant height, leaf number and bulb weight. From among the botanicals tested, tree tobacco had the best performance in controlling onion thrips and was comparable to those of dimethoate and Karate.