Management of Thrips tabaci (Thysanoptera: Thripidae) through agronomic practices in Onion field plots

Onion,allium cepa (l.) is very important and highly valuable vegetable crop all over the world. amongst the insect pests,onion thrips,thrips tabaci linedman (thysanoptera: thripidae) has been proved to be the most important factor for onion yield reduction. in the present study effects of intercropping and plant spacing were recorded in onion field plots as a management tool against t. tabaci. for this purpose,four intercrops (chili,tomato,okra and cotton) and five plant spacings (10,15,20,25 and 30 cm) were used in onion field crop. minimum thrips density per plant was recorded in onion plots intercropped with cotton during the study period of two years. the maximum thrips density was recorded in control plots (26.19±5.67),f4,250= 7.79; p< 0.001. onion plots intercropped with cotton gained the highest bulb weight and yielded maximum onion/plot followed by tomato,chilli and okra,respectively. no difference in mean bulb weight of control and onion plot intercropped with okra was recorded in the current study. however,bulb weight of onion in both of these plots was significantly lower as compared to onion plots intercropped with cotton. minimum thrips density per plant was recorded in onion plots in which plant to plant space was 30 cm followed by 25 cm,20 cm,15 cm and 10 cm plant spacing during both experimental years. the thrips density was increased with the decrease of plant to plant spacing. further,single bulb weight with 30 cm plant spacing was significantly higher as compared to lowest plant spacing (10 cm). in both years,onion plots with minimum plant spacing (10 cm) produced more yield/plot but with lowest bulb weight and vice versa. therefore,it was concluded that cotton should be intercropped with onion as a trap crop and medium onion plant spacing should be practiced for reducing thrips infestation and suitable bulb size with optimum yield. copyright 2016 zoological society of pakistan.