Fruit flies are a very real menace in the garden as they attack and destroy soft fruits. They are active in spring, summer and into autumn and affect apricot, peach, nectarine, raspberry and mandarins, as well as our favourite salad vegetable, the tomato. Capsicums may also be damaged. Fruit fly is found all along the Australian east coast and inland.
Female fruit flies lay eggs in the skins of soft fruits such as tomatoes. The eggs hatch as maggots (small white grubs) that feed in the fruit. As they feed, the fruit rots. If it is not disposed of, it falls to the ground where the maggots leave the rotted fruit, finish their life cycle in the soil then emerge as adults to continue the assault on our crops.
Controls in the past involved chemicals such as Rogor and Lebaycid. The removal of these products from the home garden market has made room for other more organic approaches to fruit fly control.
Fruit fly baits and lures
Baits and lures to control fruit fly have been around for a long time, but today there are newer baits, which are more effective. Old style Dak.Pots and Eco-Lure Fruit Fly Traps use pheromones to attract male fruit fly. They are useful to monitor for the presence of fruit fly and offer some control, but are not effective on their own.
New generation baits such as Cera Trap, Eco-Naturalure and Nature’s Way Fruit Fly Control target the female fruit fly, killing her before she can lay her eggs in our soft fruits.
Female fruit flies must feed on protein before they can lay eggs. The low toxic, organic lures attract the female by offering her the protein and sugar feed she is looking for. The insecticide spinosad, based on naturally occurring soil bacteria, is mixed into the protein bait. As the female fruit fly feeds on the bait she takes in the insecticide and dies before laying eggs.
The bait is a powder that is mixed with water then painted on stakes in the tomato or capsicum bed, or on the trunk of a fruit tree in the orchard. It isn’t put on fruit or foliage. The bait needs to be reapplied frequently, particularly after rain or a heavy watering. This is not a ‘set and forget’ control method.
Tip: To protect the baited area on a garden stake from weather, pop a container such as an ice-cream container over the top of the stake.
Other control methods
If all else fails, harvest tomatoes as soon as they begin to colour. Pick them with a small piece of stem attached, bring the fruit indoors and allow it to ripen out of reach of fruit fly.
If fruit fly does get in your fruit crops, make sure you pick up all the affected and spoiled fruit, put it in a plastic bag then let it stew in the sun for a few days to kill the larvae. Finally bury it or put it in the rubbish bin (not the compost heap).