Invasive Species Compendium

Detailed coverage of invasive species threatening livelihoods and the environment worldwide

Abstract

Experimental assessment of the impact of the introduced parasitoid Gyranusoidea tebygi Noyes on the mango mealybug Rastrococcus invadens Williams, by physical exclusion.

Abstract

The parasitoid Gyranusoidea tebygi was released in West Africa against Rastrococcus invadens. The ability of G. tebygi to control R. invadens was assessed in mango trees in Benin in 1989-90 using paired sleeve cages. In sleeve cages left open to allow parasitoid attack, G. tebygi reduced R. invadens numbers 2.7-fold within 1.5 host generations, compared to the closed-sleeve treatment. A parasitism index of 34.4% was measured in the open-sleeve treatment. On leaves without sleeves, the parasitism index was 2-fold higher, and the R. invadens population was two times less than that in the open-sleeve treatment. The lower level of the R. invadens population on uncaged leaves, compared to the one on leaves protected by open cages, was attributed to higher mortality caused both by parasitism and by abiotic factors such as rain and wind. The potential of G. tebygi to reduce R. invadens populations is therefore assumed to be higher than the paired sleeve treatments suggest.