A systems approach to fruit fly management

Fruit Fly Sept. 27, 2021

*For more than 50 years tree fruit growers have relied largely on the repeat application of toxic cover sprays to control Queensland fruit fly. This has inevitably led to issues with secondary pest outbreaks (commonly mites, mealybugs and thrips for example) as well as concerns regarding residues and insect resistance to pesticides.

Many of the pesticides that have been used for fruit fly management are being withdrawn due to global health and environmental concerns.

A systems approach based on the concept of ‘attract and kill’ has proven to be an effective alternative in many situations. Growers are encouraged to make the effort to learn how to adopt this approach to achieve a more sustainable pest management outcome.

There are several elements to a systems approach for the management of Queensland fruit fly. Each component is relatively simple and is based on our current knowledge of fruit fly biology and behaviour.

The nuts and bolts of this ‘systems approach’ are:

Protein baiting:

Protein baiting is the single most important element of this approach.

To make it work you should focus on the following points:

•    Commence your bait program early (at least two weeks before fruit become susceptible – this is often around ‘colour break’)

•    Continue baiting at least weekly until well after harvest (no residual fruit in the orchard)

•    Be prepared to bait twice (or even three times) per week during periods of high risk or high pressure

•    Bait as large an area as possible (whole orchard and perimeter spray onto vegetation if at all possible)

•    Include thickener with the bait solution at the minimum rate of 2.5 g/L (pre-mix this the day before for ease of use).

Male annihilation technique (MAT):

Male annihilation is all about taking out as many male flies from the local population as possible. This can help reduce overall numbers over time. MAT is not a substitute for protein baiting. It is simply another additive tool which can help in your pursuit of best practice fruit fly management.

•    Place MAT cups (pictured below) three times per year at the rate of 20 per hectare

•    Be prepared to put out even more in highly susceptible crops or if the pressure is high

•    Leave each MAT cup out for a full 12 months (we now recommend the biodegradable cardboard cup so they can be left out permanently)

•    MAT cups are highly effective for three months but will continue to offer benefit for up to eight months or more.

MAT cup

Monitoring:

Monitoring is essential so that you know what is going on in your crop. You will make better pest management decisions if you understand what the local fruit fly population is doing and how it is affecting your crop.

•    Monitor the fruit fly population with male fruit fly traps

•    You do not need to put out a lot of traps to get the information you require

•    For less than five hectares, 3–5 traps is sufficient. For larger operations one trap per 5-10 hectares will do

•    Understand that MAT cups will compete with male fruit fly traps

•    The absolute number of flies caught is not terribly relevant. Focus more on population trends

•    Monitoring should also include regular crop inspection by a competent scout

•    Look for evidence of fruit fly damage, fallen fruit or active flies in the field

•    Dissect damaged fruit and learn to recognise fruit fly larvae

•    Be prepared to increase frequency of applied protein bait sprays if monitoring indicates a period of elevated activity.

Sanitation:

This is all about reducing the opportunity for fruit flies to breed in and around your crop.

•    Ensure that all fruit are harvested from each block and continue baiting until all fruit are gone (either harvested or due to natural drop)

•    Remove any host trees from around farm buildings and nearby areas

•    Try to ensure that your neighbours understand the importance of either controlling fruit fly populations or removing host trees.

Cover sprays:

•    If all else fails be prepared to resort to a cover spray but try everything you can to avoid this option.

Area wide management:

All the principles mentioned above (other than cover sprays) will work better if applied over larger areas. Horticulturalists within a district would do well to manage their fruit fly populations in a coordinated and cooperative way. Nevertheless individual farms can achieve a great outcome if they religiously practice the simple steps described above.

*Written by Dan Papacek an entomologist with Bugs for Bugs which specialises in IPM. Bugs for Bugs are one of Australia’s leading suppliers of non-toxic alternatives to conventional pesticides. Their products include biological control agents, fruit fly management tools, and trap and pheromone products. Their mission is to help Australian growers achieve best practice pest management with minimal pesticides.

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