Final Report on the Use of Parasitoids to Control Sweet Potato Whiteflies in Open Arizona Agriculture
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AbstractThe effect of three different release rates (1x [label rate], 10x, and 20x the recommended rate of 10,120/acre) of the parasitoid Eretmocerus eremicus on sweet potato whitefly populations found in open fields of cantaloupe was evaluated against populations in untreated control plots. Parasitoids were released from a point source in the center of each of nine treatment plots. Whitefly population growth, encompassing all developmental stages, and rates of parasitism were monitored within a 33 ft radius surrounding the center point in all 12 plots over a 52-d period. The rates of sweet potato whitefly population increase during this time were equivalent regardless of the parasitoid release rate. Whitefly densities were not limited in any of our treatment plots when compared to those found in the control plots. Moreover, mean rates of parasitism did not increase with time nor did they differ among the three treatments or control plots (7.9 ± 6.5%). Finally, estimated rates of parasitism were density dependent responding positively to increasing host numbers. The ineffectiveness of this parasitoid in controlling whitefly populations in the field may be due to its high propensity to disperse at low host densities or to influxes of immigrating whiteflies. Hence, the use of E. eremicus alone is not an efficient means to reduce whitefly populations in melon crops in the southwestern United States.