Role of Intercropping on Predatory Thrips (Aeolothrips Spp.) for the Management of Onion Thrips (Thrips tabaci Lind) in Central Zone of Tigray, Ethiopia

Onion thrips, Thrips tabaci (Thysanoptera: Thripidae), is a major insect pest constraining onion production in Central Zone of Tigray Region, Ethiopia. Onion growers in this central zone rely on synthetic insecticides for the management of thrips; there was no other recommended onion trips management option for the area so far. Therefore, a field experiment was conducted in Axum Agricultural Research Center, Ethiopia from November 2015 to April 2016 to encourage the number of banded thrips (Aeolothrips sp) using intercropping and to determine their effects on onion thrips management. The experiment was laid out in a Randomized Complete Block Design (RCBD) with split plot arrangement and replicated three times. Onion cultivars Bombay Red and Nasik Red were used as main plot treatments and intercropping onion with three other vegetable crops viz. cabbage, carrot, lettuce and their combinations, as sub-plot treatments. Onion treated with the insecticide Lambda-cyhalothrin (Karate) 5%EC and untreated control was included as standard and control checks. The number of predatory thrips (Aeolothrips spp) were significantly higher in onion intercropped with cabbage (10.97) and cabbage + carrot (10.73) banded thrips per plant ,respectively, at 90 days after treatment and were absent in the insecticide treated plots. As a result, the number of onion thrips was significantly lower in these treatments and higher in onion treated with Lambda-cyhalothrin. The results showed that the resurgence of thrips pest as the insecticide had more adverse effect on the predator than the prey. Thus, encouraging natural enemies especially banded thrips is an important option of biological control of onion thrips in onion production in central zone of Tigray, Ethiopia.