FIELD INFESTATION AND SUPPRESSION OF THE INVASIVE FRUIT FLIES BACTROCERA INVADENS (DREW, TRSURUTA AND WHITE) ON CITRUS IN KENYA

Field infestation rates of the invasive fruit fly, Bactrocera invadens on Citrus spp. was determined at different localities in Kenya. The level of infestation varied with location ranging from 3 to 36%. At some locations, B. invadens shared the same fruit with the indigenous fruit fly, Ceratitis capitata but occurred at higher numbers than C. capitata. Among the five Citrus species sampled, sweet orange (Citrus sinensis) recorded the highest level of infestation compared with other species. There was a significant inverse relationship between numbers of B. invadens/kg of fruits and elevation at which fruits were collected. Field trails were conducted on sweet orange during the fruiting and off seasons to compare catches of B. invadens in Multilure trap baited with 6 food-based attractants (Mazoferm, Torula yeast, Hymlure, Molasses, Mango juice and Nulure). During the fruiting season, Mazoferm and Torula yeast were the most effective attractants and captured between 2.4-2.8 times more females and 3.2-4.1 times more males, respectively than the standard Nulure. In the off season, Mazoferm and Torula yeast captured between 2.5-2.7 times more females and 3.7-4.3 times more males, respectively, than Nulure. In field suppression trials using Mazoferm-spinosad bait spray, % reduction in B. invadens population relative to control was 82% at 4-weeks after bait spray, and 94% at 8-weeks after treatment application. At harvest, % fruit infestation was significantly lower in the treated orchards (5%) compared with the control orchards (39%) and demonstrates the efficacy of bait spray for the management of B. invadens on citrus.