Spatial Distribution of Psyllaephagus Bliteus and Its Impact on Glycaspis Brimblecombei Population in Eastern and Western Kenya

Abstract

Glycaspis brimblecombei Moore (Hemiptera: Psyllidae), a sap-sucking psyllid is known to cause 20-30% defoliation, crown thinning and death of eucalypts. The main natural enemy that has proved effective against this pest in Australia is a parasitoid Psyllaephagus bliteus Riek (Hymenoptera: Encyrtidae). This parasitoid reportedly spread and established unaided in areas where the G. brimblecombei is found. In 2007, Forestry Resources Research Institute (NaFORRI) released P. bliteus in Eucalyptus camaldulensis plantations in Uganda bordering Western Kenya under the assumption that it will spread and contain populations of G. brimblecombei. The current study was designed to evaluate the extent of distribution of P. bliteus and determine parasitism rate on G. brimblecombei in Western and Eastern, Kenya. During the study, three (3) E. camaldulensis plantations in Western Kenya (Busia, Bungoma and Siaya counties) and two (2) in Eastern Kenya (Ndufa and Kiamuringa Kenya Tea Development factory plantations in Embu County) were assessed. Global Positioning System Coordinates of identified plantations were recorded and ten (10) E. camaldulensis trees were randomly selected from each plantation and assessed. Four different damage categories by G. brimblecombei were assigned to sample trees through visual observation. Adult population of P. bliteus was assessed by placing two yellow sticky traps on each sample tree. Three assessments were carried out in three different months and generate data analysed was carried out using packages in R Environment. Distribution maps were drawn using ArcGis to indicate the intensity of spread of the pest in the regions of study. Tree infestations by G. brimblecombei were highly varied across the four counties (F3,1492= 7.44; p < 0.001) and time of assessment (F2,1492= 91.91; p < 0.001). Embu County had the highest G. brimblecombei populations (40.67±1.58), recorded in the month of February with damage ranging between 50–75%. This was followed by Busia (28.79±1.19), Siaya (25.47±1.86) and Bungoma (20.80±1.29) Bungoma recorded the highest parasitism rate of P. bliteus (11.61%), followed by Siaya (7.92%), Embu (5.08%) and Busia (3.54%), indicating that P. bliteus found its way into Kenya. This study provides important information on the establishment of P. bliteus in Kenya and this would guide enable initiation of implementation of Bio-control program for sustainable management of G. brimblecombei in Kenya.