Impact of the black twig borer on Robusta coffee in Mukono and Kayunga districts, central Uganda

Abstract

1 SUMMARY An outbreak of a “serious” pest of coffee was reported in Mukono and Kayunga districts in central Uganda in December 2008. In response, a survey was carried out in the two districts to determine the identity, spread, incidence and damage caused by the pest. The pest was preliminarily identified as the black twig borer, Xylosandrus compactus (Eichhoff), which was found on coffee in both districts infesting 37.5% of the surveyed Robusta coffee farms. The infestation in Mukono was higher than in Kayunga, being 50 and 8.3%, respectively. The percentage of trees attacked (incidence) in the two districts was 21.2, with 3.7% of their twigs bored (damaged). Mukono district had a much higher incidence (35.3%) and damage (4.9%) compared to Kayunga with 0.8% for both parameters. The most serious damage was recorded in Namuganga and Nabbaale subcounties in Mukono district, the apparent epicentre of the outbreak. It was evident that the pest was spreading to other subcounties surveyed within and outside Mukono district. This pest poses a threat to coffee production in Uganda and immediate comprehensive mitigation action should be taken.