Fruit Fly ID & Management
About fruit fly
Queensland fruit fly is located throughout eastern Australia. (WA is affected by Mediterranean Fruit Fly). Both damage fruit in the same way and in most cases similar methods are used to control them.
QLD Fruit Fly are smaller than regular houseflies with a distinct yellow band across their back. More often that not, you will not see the adult flies until late in the season, when populations are high and after they’ve done their damage, stinging your fruit to lay eggs from which larvae hatch and eat away the insides of the fruit, turning it to mush.
Note: The tiny flies that hover around your compost or fruit bowls are usually vinegar flies, not fruit flies as they are often called.
Below are a list of strategies recommended for controlling fruit fly. Use the strategy(s) best for your situation.
Netting physically stops fruit fly from stinging fruit, I believe it to be the best method for preventing fruit fly damage. This method is suitable for trees/crops that flower and set fruit over a short period.
Netting plants where flowers and fruit set occur over an extended period of time eg. tomatoes or berries can prevent pollination. One way around this is to gently agitate plants with your hands plants every couple of days to distribute pollen. For best success:
- Net as soon as flowering has finished and fruit set
- Ensure netting holes are no more than 2-3mm wide
- Netting applied over a frame extends the netting life and prevents stinging of fruit through netting resting on fruit
- If you have had previous fruit fly damage secure netting to trunk not to ground as fruit fly will pupate from the soil below
- Check netting each season for holes and tears
- Remove netting after all fruit has been harvested
Best used: Early in the season before fruit fly have emerged. Don’t use: On trees with fruit fly stung fruit.
Bait sprays are applied to underside of foliage or boards placed in trees (not directly to fruit). Bait sprays use a combination of a protein source (attractive to females prior to stinging fruit) and Spinosad. The idea is that female flies need to feed on a protein source prior to laying eggs. When they feed on the bait spray they die.
Example: Eco-naturelure (active ingredient: Spinosad)
Use these to trap males. This is not a control method but rather an early warning system to indicate presence of the pest. If flies are found in the trap, implement other control methods. Traps can also be used to monitor fruit fly numbers after implementing a control program to see if it is successful.
Example: Eco-lure Fruit Fly Trap (attracts Male Fruit Fly)
Cover sprays kill eggs and grubs thus breaking the breeding cycle and reducing pest numbers. Sprays based on Pyrethin or Spinosad have a low environmental impact and are based on natural ingredients. They are best applied:
- When fruit fly numbers are high or if fruit has already been stung to protect remaining unstung fruit
- Weekly for continued protection
- Early morning/late evening to limit impact to beneficials
Example: Richgro Naturally Based Fruit Fly Spray (active ingredients incl. Garlic, pyrethrins, Piperonyl Butoxide
Fruit fly resistant varieties
Grow fruit fly resistant fruit and fruiting vegetables.
My experiences with fruit fly
I first discovered fruit fly in my garden, November 2013. Why? A very mild winter, a super warm Spring or a neighbour cutting down some unmanaged fruit trees. One can only guess. Read about my experiences below…
25 Nov – Found a few small grubs in the youngberries and 1 yellow pear tomato. I suspected they are young fruit fly larvae. For the moment, I will continue to pick fruit daily, picking early and ripening inside where possible (tomatoes). Any fruit picked or collected with grubs in it is being sealed in ziplock bags and left in full sun for 7 days (longer if days not 30C plus) to kill grubs. I have netted nectarine tree (highly attractive to them) and checking underneath daily in case any have already been stung.
10 Dec – I saw an actual live fruit fly in the mango tree today and made the decision to use a bait spray on boards placed near preferred crops. One is placed 1/2 way up mango tree, the other behind tomato plants (on pool deck in shade). I figure that by not spraying tree foliage, I’m minimising pesticide contact with fruit. I have used eco-naturelure.
12 Dec – Some animal licking my bait lure boards completely clean overnight. I suspect mice who have also been eating some of my tomatoes. Will continue to use boards but have covered them in chicken wire propped up above board with timber offcuts. Flies can still get through, hopefully mice can’t.
17 Dec – The mesh on the boards has worked. Yay! Bait has stayed on for a week. Unfortunately, the loss of this food source has meant the mice have turned to the vege patch. Looks like a new post is in order 🙂
Update: Spring 2014
Instead of baking the fruit fly in enclosed bags in the sun (Yuk!), I have started freezing any fallen or fruit fly affected fruit for 2 weeks prior to disposal. This also kills the fly larvae.
Over the years, I have tried different strategies for managing the dreaded fruit fly. Early netting or bagging fruit (as soon as fruit has set) has worked best for me as it physically prevents the FF fruit laying eggs. If I do encounter fruit fly affected fruit, I freeze them or microwave prior to disposal in sealed ziplock bags.