New in-field treatment solutions to control fruit fly (VG13041)

What was it all about?

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, means that alternative control options are required.

This project aimed to assess combined control methods of perimeter protein baiting and male annihilation, and alternative chemical options, as well as finding out more about seasonal fruit fly activity in vegetables.

In the first part of the study, semi-field trials were performed to assess the efficacy of eight insecticides applied as cover sprays to fruiting capsicum and zucchini plants.

Results showed that:

• Clothianidin was very effective against Queensland fruit fly and cucumber fly
• Thiacloprid, imidacloprid, cyantraniliprole and alpha- cypermethrin 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 third trial was performed to assess a combination of perimeter protein baiting and male annihilation for management of fruit fly in a commercial chilli crop in Bundaberg. Sampling of fruit from the trial block throughout harvest found that the treatments successfully prevented infestation.

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. No larvae were recovered during winter, when fruit fly activity was low, but the control measures were not sufficient to prevent infestation outside of this period. The researchers put this down to high local fruit fly pressure at the trial site, coupled with the smaller size of the area over which control measures were applied.

Monitoring of seasonal fruit fly activity in the Bundaberg region found that traps caught most flies in spring, with a second peak in 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 tree-line, compared with those further within the crop.

Another trial on traps baited with a cucumber volatile lure found that the BioTrap was better than a Bugs for Bugs trap for cucumber fly.