Population dynamics and chemical control of onion thrips (Thrips tabaci,Lindemann)

Population dynamic studies conducted at peshawar,pakistan showed that the activity of onion thirps (thrips tabaci lindermann) was first recorded on 3rd february (1.20 thrips/plant) and reached to its peak (100 thrips/plant) during the last week of april. later,the population declined to 3.85 thrips/plant towards the end of may as the crop started to mature. population model using the meteorological data indicated that linear and quadratic components of average air temperature were important in predicting the population development of t. tabaci. however the model accounted only for 44% of total population variability. the insecticides; thiodan®,contutor®,tracer®,megamos®,and actara® were sprayed three times and data were taken at 24 hours,72 hours,seven days and 10 days intervals. except actara,all insecticides were significantly effective against the pest as compared to control maximum cost-benefit ratio was recorded for confidor (39.45) and the least was recorded for actara (3.41) treated plots. copyright 2010 zoological society of pakistan.