Exclusion is a preventative method that uses physical barriers to stop female adult fruit flies from reaching your fruit and vegetables. This method forces female flies looking to lay eggs in your crop to search elsewhere for a suitable host. Typical barriers that can be used around the home garden are nets, bags and sleeves.
Mount Alexander Shire Council and the City of Greater Bendigo, in partnership with Agriculture Victoria, produced a series of educational videos on managing Queensland fruit fly. This episode covers exclusion.
- Completely protects your crop so that you can harvest it larvae (maggot) free
- Allows produce to ripen as normal on the tree or plant
- Requires a once only application of exclusion products over your crop
- Can help protect your crop from other insect pests, as well as possums and birds
- Some exclusion products can be reused from year to year
- Relatively low cost and easy to use when compared to cover spraying
What makes it right for you?
Exclusion will be a method that is right for you if you:
- either own your home or are renting
- live in a fruit fly prone area, particularly in highly infested areas
- want to use an effective, organic method without the use of chemicals
- need your produce to ripen on the plant as it is unsuited to being picked green
- are willing and able to spend time in the garden placing barriers on plants and monitoring fruit for ripeness
- have had only limited success with other control methods such as cover spraying and baiting
- want the option of either making your own or buying exclusion products
Factors affecting success
- Integrity of exclusion barriers, i.e. well secured, and free from tears and gaps
- Timing of the placement of barriers over your fruit and vegetables
- Usage in combination with other control methods such as sanitation and pruning
- Removal of any infested fruit if barriers are placed on plants late in the season
- Exclusion can be labour-intensive and time-consuming when installing, monitoring and removing barriers from plants, particularly if you are using bags and sleeves and have a big crop
- Requires that you prune trees to a smaller size so that you can more easily install, check and remove barriers
- Integrity of exclusion products may be damaged if are not removed at the end of the season
- Barriers may not be aesthetically pleasing to the eye (if this a concern to you)
What to do
1. Select barriers that are suited to your crop needs
- Nets are suited for whole trees or whole branches, and even whole rows of crops
- Bags tend to be better for individual fruit with little or no stems
- Sleeves are better suited for covering clumps of fruit, such as plums
Note that you may need to try different barriers to see which one(s) best suit your situation.
2. Place barriers on your crops
Bags and sleeves
- place nets either directly on plants, on a frame of PVC tubes staked in the ground, or over individual tree branches
- secure nets well to the frame or the base of the tree to prevent tearing by strong winds and wildlife such as birds becoming entangled
- use a sturdy frame if you can as this will help your net last longer from rips and tears caused by branches
- secure nets at ground levels with heavy object such as bricks or logs, or use stakes/pegs to prevent fruit fly from getting inside the net
- prune trees to a smaller size so that nets can more easily be placed and removed from the tree (if you want more fruit you may have the option of planting more plants), or consider planting dwarfed varieties of fruit trees
- practice sanitation within the net
Note that if you are unsure whether there are fruit fly pupae in the ground under your fruit trees, you may want to secure the bottom of the net to the trunk base. This will prevent any adult fruit flies emerging from the ground from infesting your new season crop.
- place bags and sleeves over the fruit you want to keep
- thin (remove) any flowers or developing fruit that are not covered by a barrier from the plant
- secure bags and sleeves to the plant with tie wire, clothes pegs or string
3. Monitor your crop for ripeness
You will need to check your crop for ripeness on a regular basis. Do this by opening the barrier and looking inside. This needs to be done since many of the materials used for barriers are not transparent (see through). Also, remember to practice good garden sanitation by collecting and destroying any rotting or unwanted fruit that you find.
4. Remove barriers
At the end of the growing season, remove any barriers that you have used from the garden and store away for next season. Repair or discard any barriers that have been damaged.
When to do it
Exclusion barriers should be applied as early as possible during the growing season. This can mean as early as petal drop, indicating that pollination has occurred, or as fruit are just developing. Placing exclusion products on the plant at this time will protect your produce, since fruit flies tend to target fruit and vegetables that are maturing or ripe. If you suspect that your produce has already been stung, then remove it before netting or bagging. Note that self pollinated crops can be covered anytime before fruit matures or ripens.
Making your own
You can make your own exclusion products if you are able and willing. Some home-made exclusion products, such as cloth or paper bags and sleeves, can be made relatively easy from items that may be found from around the household. While home-made nets and frames may require a little more work. Ideally the materials you use for exclusion products should be relatively durable to outdoor conditions. Some ideas for making your own physical exclusion products are provided below.
Bags and sleeves
- Nets can be made from materials such as mozzie (mosquito) nets and gauze curtain material (1.6mm good for fruit flies and most other pests). Note that gauze curtain material may deteriorate quicker when exposed to weather.
- Nets can be made from mozzie nets, cut or sewn to desired shape and size.
- Mozzie nets can be purchased from places such as Big W, Spotlight, Bunnings (note that lace curtain material may be unsuitable as it eventually deteriorates and become unusable).
- Frames for nets can be made from materials such as electrical conduit/Polypipe (i.e. 2 inch in diameter) that does not lose its shape in the sun.
- Frames can be constructed by crossing over and securing (tie with wire) together two lengths of pipes over the tree.
- Frames can be secured in the ground by slipping end of polypipe over pickets (i.e. star pickets) in the ground.
Also consider buying umbrella and gazebo nets and frames (need to cover hole at top) which may have zipper on side for easy access.
Bags and sleeves are generally a little more easily made because of the size required and materials used to make them. For exclusion products such as bags, some gardeners have been known to use: brown paper lunch bags (which may get soggy when it rains); wax paper bags that are used for keeping mushrooms in; and mozzie netting cut and sewn to size. Sleeves can be made from materials such as mozzie netting, fly screen and gauze curtain material, also cut and sewn to desired size. Both bags and sleeves can be secured to the tree or plant with string, clothes pegs or tie wire.