Bronwyn Koll (QueenslandFruitFlyRegionalCoordinator,YarraValley)and Kevin Sanders (orchardist).
Bronwyn’s role is to help keep Queensland Fruit Fly out of the Yarra Valley. Main points of her talk:
- QFF is native to the Queensland rain forest but has for many years been found in northern Victorian fruit-growing districts – Wodonga, Shepparton, Cobram etc. Since 2013 it has become so prevalent that it is no longer monitored and the idea of fruit-fly exclusion zones has been abandoned. It was found for the first time this year in the Yarra Valley, as isolated outbreaks around Lilydale and Sylvan. There have also been outbreaks in Tasmania and WA.
- QFF has a 28-day life cycle. The adult is a red-brown colour, about 7mm long, with characteristic yellow banding on the body. The female lays her eggs under the skin of ripe fruit. In the early stages, all that can be seen is a little mark (‘sting’) on the fruit skin. The resulting larvae are creamy white with a black head, about 5 – 10 mm long. The fruit rots prematurely and falls from the tree. The larvae then pupate underground and develop into flies. These emerge from the ground and feed on protein until sexual maturity. The cycle then repeats. There could be 2 or 3 cycles in a typical Yarra Valley summer.
- There is the potential for almost every type of fruit and fruiting vegetable in the Yarra Valley to be affected, including wild blackberries, prickly pear, tomatoes, and fruit from wild trees. The commercial implications are severe, but the growers have an incentive to monitor and control, whereas it has been difficult to motivate home gardeners.
- What should home gardeners do?
- be constantly vigilant
- do not bring fruit from home gardens in other areas of the country into the Yarra Valley
- remove neglected trees
- share information with other gardeners
- set traps
- pick fruit : don’t let it lie on the ground
- net host trees
- If any affected fruit is found notify Shire Council.
- Do notcompost affected fruit: either boil it or freeze it to kill the maggots, then dispose of it in the garbage.
- Traps, baits and sprays are available at nurseries and hardware stores. A trap can also be homemade from an empty soft-drink bottle with three 10-cent size holes cut into it near the top. Use a bait made of 1 cup of fresh fruit juice and pulp mixed with one tablespoon of cloudy ammonia. Hang the trap in the tree on the shady side, about 1½m above the ground, and change the bait weekly.
- Bronwyn left a number of fliers and information sheets for members to study.
Following on from Bronwyn’s talk, Kevin Sanders spoke on apple growing in the Yarra Valley. Kevin is the Deputy Chairman of Apples and Pears Australia Ltd and has been growing fruit in the Yarra Valley for 40 years.
- Apple trees grown for commerce differ from home-gardeners’ trees in that they are far more productive, having more lots more wood and fewer leaves. Since 80% of pests and diseases occur on new and growing shoots, commercial trees are thus also less prone to problems.
- Since the mid-90s the trees have been semi-dwarf types with a very low canopy, grown 4 x 4 m apart on a V-trellis with posts and wires for support. The trees are pruned initially to have 3 narrow trunks and no branches, after which no further pruning is required.
- The apples are harvested by machine over a 20-week picking season, but next season this will be done by robots since labour costs are 60% of the total production cost.
- Each tree produces 120 apples, and with 4000 trees, this represents a yield of 20 tonnes/hectare.
- Pollination: when the trees are grown so intensively, getting enough bees is a huge problem. Kevin’s orchards have their own supply of bees: 3 hives per hectare
- Spraying: most of the sprays in use are nutrient sprays rather than pesticides. Beneficial insects are encouraged in preference. Immediately prior to rain, some fungicide is used against black spot.
The varieties grown depend on market fashions. At present Pink Lady, Gala, Fuji and Granny Smith are the most popular. There is a new variety about to be released called Kanzi.