EXPERIMENTAL ASSESSMENT OF THE IMPACT OF THE INTRODUCED PARASITOID GYRANUSOIDEA-TEBYGI NOYES ON THE MANGO MEALYBUG RASTROCOCCUS-INVADENS WILLIAMS, BY PHYSICAL EXCLUSION

The parasitoid Gyranusoidea tebygi Noyes was released in West Africa a gainst the mango mealybug, Rastrococcus invadens Williams, a pest that invaded Africa in the early 1980s. The ability of G. tebygi to contro l the mango mealybug was assessed in mango trees using paired sleeve c ages. In sleeve cages left open to allow parasitoid attack, G. tebygi reduced mealybug levels 2.7-fold within 1.5 host generations, compared to the closed-sleeve treatment. A parasitism index of 34.4% was measu red in the open-sleeve treatment. On leaves without sleeves, the paras itism index was a-fold higher, and the mealybug population level was t wo times lower than that in the open-sleeve treatment. The lower level of the mealybug population on uncaged leaves, compared to the one on leaves protected by open cages, is attributed to higher mortality caus ed both by parasitism and by abiotic factors such as rain and wind. Th e potential of G. tebygi to reduce mango mealybug populations is there fore assumed to be higher than the paired sleeve treatments suggest. ( C) 1995 Academic Press, Inc.