Resistance of Predacious mites, Euseius kenyae (Acari: Phytoseiidae) to chlorpyrifos (Dursdan

Abstract

Several strategies are employed in management of insect pests. Among these, chemical control is a priority to most farming communities where pest incidences occur while other existing options such as biological control are rarely considered. In coffee farming agro ecosystems, there are indigenous biological control agents such as the predacious phytoseiid mites, Euseius kenyae (Swirski and Ragusa) that have the potential to manage secondary pests like coffee thrips, Diarthrothrips coffeae Williams. This study was conducted to assess the population dynamics of E. kenyae and D. coffeae as well as theirinteractions under coffee agro ecosystems where various soil fertilizer sources and selective insecticides were applied as treatments. The populations of both E. kenyae and D. coffeae fluctuated during the three years study period. The E. kenyae suppressed the population of D. coffeae under various treated coffee blocks. There was negative correlation between E. kenyae and D. coffeae in year 2006 and 2008 where the increasing population of E. kenyae decreased that of D. coffeae. In year 2007, positive correlation between E. kenyae and D. coffeae was observed in some of the treatments where increased population of D. coffeae caused an increased population of E. kenyae. Euseius kenyae managed to contain the D. coffeae population to below economical injury levels (1-2 thrips per leaf) during the three years under the various coffee agro ecosystems. The use of chlorpyrifos never affected E. kenyae. Their survival and increased in number under chlorpyrifos treated coffee blocks indicated the development of resistance by the population of E. kenyae, hence the possibility of using them as a component in an Integrated Pest Management strategy in coffee