Parasitism of Psyllaephagus blitues (hymenoptera: encyrtidae) a biological control agent of the eucalyptus pest Glycapsis brimblecombei ( hemiptera : aphalaridae) in selected agro ecological zones of Uganda.

Abstract

Eucalyptus is important in plantation forestry in Uganda this is because of early rotation, high coppicing ability, and can be grown in most parts of the country however invasive pests like Glycaspis brimblecombei Moore ((Hemiptera: Aphalaridae) are threatening Eucalyptus plantations. The successful biological control results obtained elsewhere using Psyllaephagus bliteus Riek (Hymenoptera: Encyrtidae) prompted its importation into Uganda. To assess its establishment in Uganda, the level of parasitism by P bliteus, the factors that affect parasitism level, and the dispersal range of P bliteus were determined in Central wooded Savannah and Northern Moist Farmlands AEZs of Uganda. For each site data was collected once every month for six months. 10 leaves were sampled from each section of the tree crown from 10 trees per plantation, 8 sites were sampled including 4 Eucalyptus camaldulensis and 4 GC plantations, 3 silvicultural practices were assessed. Mean parasitism was 49.50%, Differences in parasitism in the two AEZs were not significant (p = 0.17). A Significant difference in parasitism was noted between E. camaldulensis plantations and GC plantations (p = 0.001). No statistical differences is noted on the different Eucalyptus age groups, on vertical sections of the crown and different leaf surfaces. Silvicultural practices did not affect parasitism and mummified nymphs of G. brimblecombei were got 10 km away from release sites. Our results demonstrate that P.bliteus has been established and since establishment correlates with control I infer substantial control of G. brimblecombei under field conditions in tropical zones like Uganda however longer field studies might be necessary to better understand the host and parasitoid relationship including seasonality and success in different parts of the country.