Introduction. Timing of management practices requires an
understanding of pest population dynamics in given cropping systems. Our study was
designed to establish the population trends of B. invadens in mango
orchards and to determine if population fluctuations were reflected in fruit infestation
levels during changes in mango phenology. Materials and
methods. Bactrocera invadens flies were trapped weekly from
February 2011 to November 2012, using methyl eugenol and DDVP (dichlorvos) insecticidal
strips. Trapping was done in three mango orchards in the Luweero district of Uganda’s Lake
Victoria Crescent. Mango fruit samples were incubated for the retrieval of puparia to
calculate positivity (proportion of fruits infested) and fruit infestation indices (number
of puparia per kg of fruit) for each stage of fruit maturity. Results. Mean
trap catches of adult B. invadens varied significantly over the months
(range : ~11 flies per trap per day (FTD) to over 590 FTD; P £ 0.0001).
During each year, infestations peaked during June-July and January-February. Trap catches
were higher in the major fruiting season compared with the minor fruiting season and were
the highest when mango was at the physiological maturity and ripe stages. Fruit
infestation and positivity were highest for fruit at the physiological maturity and ripe
stages and lowest at the fruit set stage. Discussion. Our findings show that
B. invadens is present year-round and all stages of mango fruit
development are susceptible to attack. Thus, control measures should be implemented
throughout the year and preferably started at fruit set to lessen fruit fly population
build-up and damage to fruits.