Effect of Migration, Temperature, and Precipitation on Thrips Infestations in South Texas1

A two-year study on onion thrips (Thrips tabaci Lind.) yielded data which indicated that concentrated migrations of thrips into onion fields do not occur in South Texas. Thrips movement into onion fields lessened as other host plants became lush and onions approached maturity. Precipitation and mean daily temperatures below 50 degrees F. reduced thrips movements. Driving rains reduced thrips 58 degrees F. favored destructive infestation. Heavy infestations resulted from build-up in the field and not from thrips movement into the field.