Field Evaluation of Eretmocerus eremicus Efficacy in the Control of Sweet Potato Whiteflies Infesting Melons

The effect of three different release rates (1x, 10x, and 20x the recommended rate of 10,000/acre) of Eretmocerus eremicus, a whitefly parasitoid, on sweet potato whitefly populations in cantaloupe were evaluated against populations in untreated control plots. Parasitoids were released from a point source in the center of each of nine treatment plots. All stages of whitefly development were monitored within a 10-m annulus surrounding each release point in all 12 plots, as were rates of parasitism. This occurred over a 52-d period from July 21 through September 11, 2001. The rates of sweet potato whitefly population increase during this time were equivalent and independent of the parasitoid release rate. Whitefly densities were not controlled in any of our treatment plots, nor in the controls. Moreover, rates of parasitism did not increase with time in any of the treatment plots and did not differ among the three release rates (22.0 ± 16.2%). Hence, Eretmocerus eremicus, by itself, is not efficient as a means to control whitefly populations in melon crops in the Southwest US. The ineffectiveness of E. eremicus to control whitefly populations in the field may be due to its propensity to dispersal at low host densities