FRUIT FLY CONTROL
Article from Organic Gardener October 2016 by Justin Russell
When it comes to homegrown fruit, public enemy number one in my part of the world is Queensland fruit fly. Bactrocera tryoni is a little wasp-like insect that’s about the same size as a housefly but is gold and black. It’s native to the rainforests of subtropical and tropical Australia, but with a warming climate and the expansion of commercial and backyard orchards, it has gradually spread into warm-temperate zones up and down the east coast and adjacent inland. It’s now endemic to parts of Victoria , and has even popped up a couple of times across the ditch in Auckland. On each occasion it was successfully eradicated. Fruit fly is a major problem because of its breeding habits. Female flies mate, then buzz around looking for a nice bit of fruit in which to lay their eggs. These hatch into larvae, which feed on sugars in the flesh of the fruit and spread a bacteria that aids in the decomposition process. The result is rotten fruit. This falls to the ground, allowing the fly larvae to burrow into the soil where they pupate, then emerge about 10 days later as a new generation of adult flies. The entire lifecycle takes about a fortnight.
Very dry weather puts a halt to the breeding cycle and heavy frost kills off overwintering adult flies. But in favourable areas that experience warm, wet summers, fly numbers build to plague proportions, 'stinging' and ruining pretty much every piece of fruit available. Commercial growers and backyard orchardists alike once kept flies under control by using toxic pesticides such as Lebaycid. This was banned in 2015 by the Australian government, but many growers now use dimethoate as an alternative. This is a non-selective chemical, which essentially means that it kills any insect it comes into contact with. It is, therefore, highly toxic to bees and other beneficials.
To control fruit fly organically, you have a few options. One is to create a physical barrier that prevents the female fly from accessing fruit. This technique is known as exclusion and involves the use of fine-weave netting or small bags to protect ripening fruit. The former can be used to cover an entire tree/bush, or in the case of large trees, just a couple of individual branches. Bagging can be used to cover individual pieces of fruit, or fruit clusters. Exclusion is highly effective, if a bit fiddly.
As for chemical control, there are a few certified organic products available. These range from attractant baits that simply lure the flies and drown them in a trap (eg Cera Trap, Wild May), to baits that contain a lure, along with a naturally occurring pesticide called spinosad that kills flies when ingested (eg Eco-Naturalure, Nature's Way Fruit Fly Control). Some gardeners swear by traps, others prefer baits. A combination of both might prove the best method of control.
The final piece of the fruit-fly puzzle is free, simple and within the grasp of every gardener – cleanliness. When it comes to fruit fly, it is next to godliness. If you diligently pick up every piece of fallen fruit from the ground and either solarise it in a plastic bag left in the sun or seal it in a bag and bin it, you’ll put a significant dent in your garden’s fly population. Heat kills the maggots. The best advice I can offer is to see fruit-fly control in two ways – as a suite of techniques that work more effectively together than in isolation, and as an act of neighbourliness. It takes a village all working in unison to keep fly numbers down, so do your bit, and encourage your neighbours to play their part as well. Who knows, you might get a bag of beautifully ripe, organically grown fruit passed across the back fence for your trouble.
NB: Gardeners in WA and SA might encounter similar issues with Mediterranean fruit fly. This is an introduced pest, but is controlled similarly to Queensland fruit fly.
Stop fruit fly ruining your
beautiful fresh fruit -
we use Biotraps & Nets
1.When the fruit has been pollinated, after flowering, put out your traps. Traps work for 3 months before they need reloading with bait & attractant. Each trap will protect about 15 square metres
2. You can also cover your fruit tree with a very fine net ( holes between 1-3 mm ).
Nets are the most effective way to stop fruit fly, other bugs and birds eating and damaging your fruit.
3. Remove obviously damaged fruit from trees and pick up any fruit that has fallen on the ground
4. Put fallen/waste fruit in a plastic bag and leave in the hot sun for a week or longer if it is cool weather. This will kill the maggots. Put in another bag, to double the bagging, and bin it.
5. Fruit flies in the affected fruit can also be killed by heating fruit up. You can boil, bake or microwave the fruit.
PLANTING BARE ROOT TREES
Information taken from Flemings Nurseries pocket guide
It is critical to prune a bare rooted tree prior to planting. Remove 30% - 50% of branches from the tree in an even manner with clean secateurs. This will bring the tree back into balance and ensure it flourishes in spring, as well as helping to form a strong framework of branches.
Prepare the hole that is one-and-a-half times the size of the root system. Place a shovelful of soil back into the hole as a loose, soft bed for the roots to sit on before filling the rest of the soil around the roots.
Plant the tree to the soil level. Once you have planted the tree, lightly pack the soil down with your foot.
Make a small well around the base of the tree, above the root zone.
Water in with a bucket of water at the time of plant the tree and weekly as it gets warmer.