Injury and control of onion thrips (Thysanoptera: Thripidae) on edible podded peas

Harvests of edible podded peas from commercial fields in upstate New York during 1984 contained two types of injury previously unreported in the United States. Damage to pods consisted of either small raised bumps or scars appearing as silver mottling. Field-sampling indicated the presence of onion thrips, Thrips tabaci Lindeman, so greenhouse and field tests were designed to assess its ability to cause this injury and strategies for control. Results from greenhouse and field trials demonstrated that the scars were caused by T. tabaci. In greenhouse trials, T. tabaci reproduced on peas and caused scars. A single application of parathion at the prebloom or bloom stage was effective in eliminating all thrips and scarring, whereas an application at pod initiation allowed a low but noticeable level of damage. In field trials, applications of parathion and dimethoate provided comparable control of scars. In one field trial it was necessary to apply an application at either the prebloom or bloom stage, followed by an additional application at the next crop stage (i.e., bloom or pod-initiation stage, respectively), to achieve greater than 70% scar-free pods. Counts of total thysanopteran larvae in treated plots before harvest indicated that both insecticides were effective in reducing larval populations. In another field trial in which thrips populations were much higher, no treatments were effective in reducing scarring injury. In greehouse and field trials the occurrence of bumps was not reduced by the use of insecticides, nor did it appear related to thrips numbers, thus indicating that they were not the cause of this blemish