In-field management of fruit flies in fruiting vegetable crops has relied heavily on regular cover sprays with dimethoate and fenthion. However, recent restrictions in their use, and the possibility of further future restrictions, mean that alternative control options are required. The project aimed to assess a combination of perimeter protein baiting and male annihilation, and alternative chemical options, as well as obtaining data on seasonal fruit fly activity in vegetables.
Semi-field trials were performed to assess eight insecticides, applied as cover sprays to fruiting capsicum and zucchini plants, for efficacy against Queensland fruit fly, Bactrocera tryoni, and cucumber fly, Zeugodacus cucumis. Clothianidin was very effective against Queensland fruit fly and cucumber fly. Thiacloprid, imidacloprid, cyantraniliprole and alphacypermethrin were also very effective against Queensland fruit fly, but less so against cucumber fly. Bifenthrin, spinetoram and abamectin demonstrated a suppressive effect. Alpha-cypermethrin, bifenthrin and dimethoate were linked to higher incidence of aphid and silverleaf whitefly infestation. A laboratory trial, in which Queensland fruit fly were exposed to dried insecticide residues on capsicum fruit, found that efficacy of thiacloprid was comparable with dimethoate, and spinetoram had a suppressive effect. Chlorantraniliprole and flubendiamide were ineffective.
A trial was performed in a commercial chilli crop in Bundaberg to assess a combination of perimeter protein baiting and male annihilation for management of fruit fly. Sampling of fruit from the trial block throughout harvest found that the treatments successfully prevented infestation: no fruit fly larvae were found in any sampled fruit (a total 6966 fruit, 91 kg), with an upper infestation level of 0.04% (95% confidence). For comparison, sampling was also conducted in a second block, where regular cover sprays with dimethoate, trichlorfon and methomyl were applied. Seven flies were found in fruit sampled from the comparison block (3048 fruit, 49 kg), with an upper infestation level of 0.21% (95% confidence).
The trial was repeated on a smaller scale in a research planting of capsicums at Bundaberg Research Facility, using a combination of perimeter protein baiting, male annihilation, and fortnightly cover sprays with spinetoram. A total of 12,995 fruit (2488 kg) were sampled. No larvae were recovered during winter, when fruit fly activity was low; however the control measures were not sufficient to prevent infestation outside of this period. The high local fruit fly pressure at the trial site coupled with the smaller size of the area over which control measures were applied were most likely critical factors.
Monitoring was performed to obtain more information on the seasonal activity of fruit flies in vegetable crops in the Bundaberg region. Peak trap catch occurred in the spring, with a second peak in the summer. Monitoring also indicated an edge effect, with more flies caught in traps located along a tree-line, or within the crop close to the treeline, compared with those further within the crop. A trial targeting cucumber fly, using traps baited with a cucumber volatile lure, found that the BioTrap (BioTrap Australia Pty Ltd) was a better performing trap type for this species, catching an average of 9.1 cucumber flies per trap per day, compared with 0.7 cucumber flies per trap per day caught by Bugs for Bugs traps (Bugs for Bugs Pty Ltd). The average sex ratio of trapped flies was 74:26 female:male. However, further trials performed in the Fassifern Valley failed to catch cucumber flies.
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