Improved Monitoring Program for Delia antiqua (Diptera: Anthomyiidae)

Abstract

A vertical, two-sided sticky trap consisting of non-ultraviolet reflective, whitepainted cardboard was developed for monitoring activity of adult Delia antique (Meigen) in commercial onion fields. A total trap surface area of 308 em2 was efficacious and economically desirable for trapping. Traps painted white were four times more attractive to D. antique flies than traps painted yellow, and were similar in attractiveness to horizontally oriented yellow sticky traps baited with onions. Traps placed 20-30 cm above a bare soil field captured more D. antique flies than traps at higher elevations. Within a mature onion stand, male fly captures increased linearly with trap height, whereas females appeared to prefer areas within the canopy. The most appropriate location for capturing males and females in a mature stand was just below the top of the crop canopy. Captures of the flies as influenced by trap direction followed a sinusoidal regression model, but combined trap catch on the complementary sticky trap faces was not significantly influenced by direction. Trap catch would be optimized by placing traps just inside the perimeter of an onion field with a spacing of 100 m between traps. A monitoring program using white sticky traps was as effective and considerably more cost efficient than a previous monitoring program that used yellow sticky traps baited with onions.