QUARANTINE EVALUATION OF EXOTIC PARASITOIDS OF THE SWEET-POTATO WHITEFLY, BEMISIA-TABACI (GENNADIUS)

Nineteen strains of parasitoids belonging to the genera Eretmocerus an d Encarsia were evaluated as potential biological control agents of th e sweetpotato whitefly, Bemisia tabaci on melons. Of these strains, th ree are undescribed species of Eretmocerus, two collected from Texas a nd one from Taiwan. Percentage parasitism and numbers of hosts attacke d were measured on melon plants in the greenhouse. Percentage parasiti sm was found to decline with host numbers and was described by an expo nential decay function. Highly significant differences were found in b oth numbers of hosts attacked and in percentages of parasitism among t he different strains, but no strong evidence was found to indicate tha t Eretmocerus species are better parasitoids than Encarsia species, or vice versa. The evaluations indicate that a species of Encarsia nr. p ergandiella from Brazil (identification number M94055) appeared to be the most promising parasitoid of B. tabaci in a melon crop.