Integration of soil fertilizers, selective insecticides and predacious mites for the management of Cofee insect pests in Kenya
Overreliance on residual insecticides to manage insect pests such as Coffee Berry Borer (CBB), Hypothenemus hampei (Ferrari) a primary pest of coffee, has resulted in many environmental and human health problems. Such problems related to CBB management among other pests signified the need to develop improved and effective insect pests control strategies. Poor plant health compromises crop yield and quality while possible temporal and spatial changes in the distribution of pests affect choice of insecticides used by farmers. Current study investigated the viability of a three-pronged coffee farm management strategy that combines use of selective insecticides, conservation of biocontrol agents and improved plant health through a field trial that was laid out at Coffee Research Station (CRS) for three years (2006- 2008). The study focused on H hampei, a primary/major coffee insect pest and Coffee thrips, Diarthrothrips coffeae Williams as secondary/minor one. Prior to this, common insect pests and predacious mites present in coffee growing agro-ecozones (UMI, UM2 and UM3) were established and their distributions determined using a field survey. Existence of predacious mites with resistance to chlorpyrifos commonly used in coffee to control primary pests was determined from mites populations collected from coffee farms and multiplied in the laboratory before bioassay on their sensitivity to chlorpyrifos was conducted. The coffee agro ecosystem exhibited a complex of insect pests. Twenty one (21) insect pest species attacked coffee according to the survey. Among these, ten (10) were common and adapted themselves to the three coffee growing agro-ecozones. The agro-ecozones were rich with biological diversity of predacious phytoseiid mites. A total of twenty nine (29) species inhabited coffee and are known for predating secondary insect pests such as D. coffeae. Euseius kenyae (Swirski and Ragusa) was most common species and adapted to the three coffee agroecozones. Some strains of E. kenyae were resistant to Chlorpyrifos and other similar chemical compounds regularly used in management of primary insect pests. Strains with resistance ratio of 39 times and also resistant to 200% field rate of chlorpyrifos when compared with susceptible strain were detected. The relationships between E. kenyae and D. cojJeae on coffee faim showed a negative correlation. Chlorpyrifos was found safe to use in coffee especially where strains of E. kenyae resistant to Chlorpyrifos occurred. The use of Spinosad and chlorpyrifos when integrated with balanced compound fertilizers (N.P.K. 17:17:17, Organic compost and N.P.K. 22:6:12) were equally effective in controlling the Coffee Berry Borer. The coffee yield and quality had no significant difference (P>0.05) under the same integrate. Yields ranged between 1187.5 - 2844.3 kg/ha while coffee grade AAlAB was between 71.1 - 89.2%. The organic compost (9.99 mites per sample) significantly (P < 0.05) conserved the predacious mites, E. kenyae when compared with N.P.K. 17:17:17 (5.25 mites per sample) under insecticide treatments. The employment of biocontrol agents (predacious mites) to manage secondary pest (thrips) with selective insecticides and balanced crop nutrition incorporated to control the primary pest (Coffee Berry Borer) was established as a suitable integrated pest management system in coffee.