Abstract:
Damage by fruit flies (Bactrocera dorsalis) poses a formidable threat to fruit
cultivation in Sri Lanka particularly in the dry zone. Synthetic pheromone traps
containing methyl eugenol have been used to manage fruit flies. However, the rapid
evaporation of pheromones under high temperatures in the dry zone and the increased
cost of traps are significant drawbacks. This study aimed to design traps using locally
available materials to facilitate the slow release of pheromone and evaluate their
efficiency for trapping fruit flies. The traps were constructed by using readily
available materials: a transparent plastic bottle (500 mL), PVC pipe (diameter 2.5
cm), plastic lid (diameter 5.5 cm) and a plastic straw (diameter 5 mm). Four
treatments were tested based on the material inside the straw for absorbance and
retention of pheromone methyl eugenol: (1) plastic straw infused with tea residue, (2)
plastic straw infused with elephant dung, (3) paper straw filled with cotton wool and
(4) the standard synthetic pheromone trap as the control. Following a completely
randomized design, 60 traps were employed with 15 traps per treatment. The traps
were installed in a guava cultivation in Galgamuwa. The number of insects trapped
in each trap was counted at 72-hour intervals for 45 days. Trapped insect counts were
analyzed using a repeated Poisson regression model. The results indicated that the
tea-residue-filled straw traps were the most effective for trapping fruit flies and had
the longest period of efficacy (p<0.05). The least effective traps were those using
paper straws filled with cotton wool. This study provided innovative methods of
trapping fruit flies more efficiently and for an extended time period using materials
abundantly available in the local environment. These methods offer a viable
alternative for monitoring and managing these pests in fruit cultivation in the dry zone
of Sri Lanka.
