Influence of shade systems on spatial distribution and infestation of the Black Coffee Twig Borer on coffee in Uganda

Abstract

Studies were conducted to determine spatial distribution and effects of shade systems on Xylosandrus compactus infestation on coffee. Number of twigs varied significantly (p<.0001) within canopy portions with the highest (17.7±6.1) in upper and least (9.1±4.6) in lower portions. Percentage of infested twigs and number of X. compactus entry holes varied significantly (P<.0001) within canopy and along twigs respectively. The highest percentage of infested twigs (10.7±15.9%) was in the middle whereas, the lowest (3.2±7.2%) in upper portion. The highest number of entry holes (0.9±0.7) was on basal and the lowest (0.3±0.6) on tip section of twigs. Tunneling by X. compactus was neither inclined towards base nor the tips of twigs. Percentage canopy cover varied significantly (P=0.0276) across shade tree species; with highest (60.0±26.5%) on jackfruit tree and the lowest (11.7±7.6%) on Chinese silk tree. Percentage of infested trees and twigs varied but not significantly (P<0.05) across shade categories and tree species. Coffee under full shade had the highest percentage of infested trees (70.8±27.8%) and twigs (14.8±18.3%); whereas, coffee under full sun registered the lowest (45.8±17.3 and 5.7±9.1% respectively). However, ANCOVA showed that shade and percentage canopy cover of Albizia, jackfruit and mango tree species had a significant (at P<0.05) positive influence on X. compactus infestation. The highest percentage of infested trees (77.8%) and twigs (15.7%) were observed on coffee under Ficus natalensis; whereas coffee under Maesopsis eminii had the lowest (44.4% and 1.5% respectively). These studies provided vital preliminary ecological information for designing and implementing appropriate management strategies for X. compactus.