The main pest fruit fly present in parts of the Goulburn Murray Valley is the Queensland fruit fly (Qfly). It’s not unknown for Qfly to cause 100% crop loss.
The adult Qfly is slightly smaller and less stocky than the common house fly. It is reddish brown to dark brown with white to yellow stripes and patches on its body. It has two wings which are mostly clear except along the outer edge and one darker stripe near the body.
Qfly eggs are very small – just about 1mm long – thin, and shaped like a pearly white banana. Eggs are laid through the skin of ripe, or nearly ripe, fruit or even in soft unripe fruit if there’s nothing else around. Maggots hatch out two or three days later and eat into the fruit with the help of some bacteria that live in the fly and its maggots. The fruit goes rotten and drops to the ground and the maggots hop out and wriggle into the ground to become pupae. These pupae are white to brown, football (Rugby) shaped pellets from which adult flies emerge some two or three weeks later.
What’s happening now – in September?
There are about 400 fruit fly traps out in the GMV and they are being checked by officers from the State Government (78 traps) and representatives for the GMV (314 traps). Because it’s been so cold in the GMV there have been very few flies trapped – only 21 from the State Govt for August 2017 – a lot fewer than the 73 flies trapped in August 2016 – and also only 21 from the other 314 traps.
Adult flies are now waking up after their winter down-time – a type of hibernation where they just hang on until it’s warm enough to fly and mate. Dense, evergreen trees like lemons are favoured winter refuges. The weather’s starting to warm up, in patches at least, so adult flies in those areas are now looking for carbohydrate and protein: carbs for energy and protein for sexual maturity. They used up most of their reserves to survive winter and now need more. Carbs can come from flowers (nectar) and protein from yeasts, fungi and bacteria growing on branches.
What can you do about this, right now?
Flies might mate in September if it’s warm enough – they mate at dusk but only if it’s 16˚C or more at sunset. If there are areas where this occurs flies will mate and then lay eggs into fruit one or two days later.
Look out for black marks and soft spots on early ripening fruit that might indicate fruit fly stings. If you cut suspect fruit open and hold it up to the light you may be able to see eggs and young larvae glistening in the fruit pulp close to the fruit’s surface, just under the skin.
If you have any late-hanging autumn fruits (like pomegranates, quinces and apples) or early fruiting fruit such as loquats, and you don’t want to use them, pull them off, or rake them up and feed them to the chooks of destroy them in plastic bags or by deep burial. NOT the compost heap! It’s warmth and humidity provides one of the best spots for them to survive – not die.
If you have lemon trees and had fruit flies last season try putting a male or female fruit fly trap or two nearby to check if these pests are starting to move.
Do you like fruit fly free tomatoes? Try planting out some seedlings or grafted plants now in a warm spot so you can get fruit before Christmas. After that, fruit flies are most abundant in the GMV. Cherry and Roma type tomatoes are a little more resistant to fruit fly attack than larger, softer, more wrinkled tomato varieties.
More information in the next edition of Fruit Flies & You………… ……..until then, stay fruit fly free! Andrew