Losses in Onion (Allium cepa) Due to Onion Thrips (Thrips tabaci) (Thysanoptera: Thripidae) and Effect of Weather Factors on Population Dynamics of Thips

4 Abstract: Pakistan is sixth largest exporter of onion bulb in the world and its share in international market is 3%. The present studies were conducted during 2008-2010, the results revealed that genotype 'VRIO-3' was highly susceptible one having 181.67 thrips per plant. The genotype "Desi Large" was moderately resistant having 94.20 thrips per plant. On average about 37% losses in yield per bulb of onion was recorded due to thrips as compared with sprayed crop. Effect of weather factors on thrips colonization depicted that heavy rainfall and low temperature had negative correlation with thrips abundance. Stage specific thrips abundance survey revealed that thrips were high on crop when it was on 5-7, 8-12 leaf stages as well as bulb initiation stage 1, as compared to other leaf and bulb developmental stages on all other genotypes. The present studies conclude that 3 sprays of insecticides can save PKR 174380 per acre saving 37.4 % losses incurred by the pest. Survey of susceptibility of onion cultivars revealed that there is scarcity of thrips resistant varieties in agro-ecosystem of Punjab-Pakistan. So thrips resistant varieties must be developed to combat menace of thrips attack.