FAQ

WHAT ARE FRUIT FLIES?

When we talk about pest fruit flies that damage our fruit and vegetable crops, we refer to flies in a specific family called Tephritidae. In contrast to these flies, flies in the family Drosophilidae are the tiny ferment or vinegar flies that we see hovering around over-ripe fruit in the kitchen or farm packing sheds. The former, true fruit flies, with head, thorax and wings quite visible, attack fresh fruits growing on plants. These true ‘fruit flies’ are larger, colourful flies generally about 5-8mm long. These are the culprits that damage susceptible growing fruits and vegetables.

We recognise eight major fruit fly pest species in Australia. One (Mediterranean fruit fly) in Southwestern Australia and seven in Northeastern Australia. In Southeastern Australia, only one species, the Queensland fruit fly, occurs. While most of these species attack fruit crops, the Queensland fruit fly is ‘public enemy no. 1’. Another species, the cucumber fly, specializes in attacking cucurbit crops such as pumpkins, zucchinis and melons. 

For more information on the pest species, we recommend reading ‘The Fruit Fly Management Guide’ that is available through contacting us via this website.

FRUIT FLY BIOLOGY

The first stage in the fruit fly life cycle is when the female lays eggs just under the skin of the fruit at the mature green to ripe stage. For many fruits such as citrus and persimmons we can recognise this by small black spots on the fruit surface, while for fruits like mangoes and stone fruits, the so-called ‘sting’ marks are not so obvious. After the eggs hatch, the larvae feed on bacteria on decayed fruit tissue and move towards the fruit centre. By the time the larvae are fully mature the affected fruit drops to the ground. At this point the larvae crawl into the top 25-50 mm of soil and transform into the pupa. From the pupa the new adults emerge, fly away and begin a new life cycle in new host plants. Over a three-month period, each female fly can produce up to 1000 eggs.

The new adult fruit flies can move over very large distances and eventually find new fruit host plants to occupy. Our research has demonstrated that about 80% of the females that enter an orchard or backyard fruit tree are immature and need a protein diet to develop eggs and mate to have their eggs fertilized. The remaining 20% of the females that arrive are mature with fertile eggs. These flies are not attracted to and don’t feed on protein as all they seek are ripening fruit in which to lay their eggs.

FRUIT FLIES IN THE HOME GARDEN

In regions where fruit flies occur, the largest fruit fly populations are in suburban areas, thus causing major problems for home gardeners. These large populations result from fruit flies breeding in major host fruits that are growing in parks, along water courses and in home gardens where no pest management treatments are being applied. In Southeast Queensland, for example, the large urban region from the Gold Coast to the Sunshine Coast creates ideal conditions for the build up of large numbers of pest fruit flies. While these flies cause major problems for home gardeners, they also can migrate westwards into commercial plantations. In discussing fruit fly management to reduce crop losses, we have to devise different strategies and/or treatment rates for the home garden due to the very large populations and the potential of invasion into one lot from uncontrolled neighbouring backyards.

FRUIT FLIES IN COMMERCIAL PLANTATIONS

In most countries, especially in the tropics and subtropics, there are a number of fruit fly species that attack a wide range of fruit and vegetable crops that are grown commercially. Different levels of crop losses can be experienced while some cultivars such as stone and pome fruits, carambola, feijoa, persimmon and guava to name just a few, can have up to 100 percent loss. In citrus crops in eastern Australia, most fruit fly damage is caused to early season (Autumn) varieties especially if a wet Autumn is experienced.

Other citrus crops are mostly Winter maturing when fruit fly populations are absent or in very low numbers. In cucurbit plantations such as zucchini and pumpkin squash, specific fruit fly species such as the cucumber fly in eastern Australia, can cause very large crop losses. This fly often attacks the female flowers of pumpkins, even before fertilization causing a large loss of flowers and subsequent poor fruit set.

In Australia there has been a significant reduction in permits for the use of insecticide over sprays. Consequently, growers now have to use other methods based on protein baits, traps and lures. Because there are a very large number of fruit and vegetable varieties grown over a wide variation in climate types, the application of these techniques often require adaptation for each farm. In summary, the crop type, cultivation method, climatic zone and fruit fly population all have to be considered in order to achieve successful outcomes.

FRUIT FLY PEST MANAGEMENT

In the absence of insecticide cover sprays, the main fruit fly control strategies available can be summarised as follows –

Physical control – using netting or bagging of individual fruit

Protein baiting – applying spot sprays of a protein lure plus registered toxicant

Trapping – Using the Fruition Nova female fruit fly trap.

In home gardens, pruning of trees to a manageable size and covering the tree with netting after fruit has set is a good option. After harvesting the net can be removed and stored for the next season or placed over the next developing crop.  Alternatively, Fruition Nova female traps combined with weekly applications of protein bait sprays are generally successful. Because urban lots are under excessively high fruit fly pressure from breeding in abundant host plants over a large area and also from nearby lots where the pest is not managed, a higher density of Fruition Nova traps is recommended.

For commercial fruit tree crop growers, a combination of weekly applications of protein bait and Fruition Nova female traps set across the plantation generally achieve a high level of success. Protein baits are important and effective because some 80% of all female fruit flies that enter a crop are immature and seek a protein diet to develop fertile eggs. However, the remaining 20% of female fruit flies are not targeted by the protein bait but are attracted to the Fruition Nova trap. This is why the combination of both methods is successful.

Important:

The benefit of the Fruition Nova trap relates to comprehensive research successfully undertaken to identify naturally-occurring chemicals and develop a lure that mimics the odour of ripe fruit in nature, in order to attract the female fruit fly which does the damage by laying her eggs into the fruit. This solution is safe to humans and the environment as no toxicant is used. The sticky surface of the trap traps the fruit flies.