For a Queensland fruit fly free garden – act now!

Robin Gale-Baker, from Sustainable Macleod, discusses Queensland fruit fly. This is one of a series of articles she has written about growing techniques (see right hand sidebar). She has also written a number of articles about growing various vegetables, herbs and fruit trees.

January 2024 article

If you were hit by an outbreak of Queensland Fruit Fly (QFF) this season, now is not the time to give up. In fact, it is the time to get busy to lower your risk of an outbreak next season.

The key task is to prevent QFF larvae pupating in the soil. If there is no QFF emerging from your soil next spring, then you are well ahead when it comes to a QFF-free orchard and veggie garden. And, you really don’t want to be spending money on lures for QFF that you have bred yourself!

To this end, pick up any fallen fruit daily and strip any fruit tree plus any tomato, chilli and capsicum plants that are infested. Larvae will emerge quickly from fruit laying on the ground (and can even drop from trees) and will burrow into the soil, beginning the long pupation process to emerge next season. This fruit should be:

• Double bagged in black plastic and put in a sunny place for 14 days to solarise the fruit and kill the larvae; or
• Frozen for 48 hours; or
• Microwaved for 10 minutes; or
• Baked in a hot oven for 10 minutes.

Place the treated fruit and vegetables in the waste bin – not in the green bin.

Do not compost fallen or infected fruit. Compost is QFF heaven! They breed in the warmth of the heap and, as you spread your compost, you also spread QFF. Make sure that any vegetable matter is buried in your heap and not exposed to QFF. Also, avoid pulling out plants such as tomato vines with fruit attached and leaving these on the ground. Bin them straight away.

Females will die off in autumn so, if no females are pupating in the soil, you only need deal with the males. Most males will die before winter, but some young males will survive, over-wintering in groups (leks) of about 10 in the canopy of trees, in particular lemon trees. In mid-autumn, place lures with Wild May in them in the canopy of lemon trees (if you have them) or other trees (otherwise) at a height of 1.5-2 metres, to deal with the males. Check the lures weekly as the liquid evaporates.

Wild May is a pheromone that smells like the female and attracts the males. It is organic. It can be difficult to find but should be available from the Sustainable Macleod shop in the autumn at cost price.

If you have chooks (or can borrow some short term) then you are in luck. Chooks scavenge for larvae and will clean the soil like no other. They are truly the gardener’s best friend in relation to QFF.

It can be very discouraging to endure a QFF outbreak and I have heard many a person say that they are ‘giving up for this season’. But that will simply prolong the agony into the following season. Good garden hygiene, proper disposal of infected fruit and using lures proactively during autumn and winter will position you well for a great harvest next summer.

July 2023 article

Now is the time to begin your campaign against Queensland Fruit Fly (QFF). Don’t delay! This pest is the scourge of fruit and vegetable growers throughout the northern suburbs and without doubt will extend its reach this season. The good news is that, after a number of years trying to achieve QFF free fruit and veggies, the Sustainable Macleod Community Garden did so last season. QFF was present – caught in lures and traps – but no produce was infested.

Here’s how it was done:

• August: all leftover fruit still on trees was removed (excluding citrus).
• August onwards: Wild May lures were placed in fruit trees. The males are attracted to these and indicate the presence of QFF. Check them weekly and top them up.
• September onwards: Ceratraps were hung in trees. Ceratraps are a protein trap that attracts males and females. Ceratraps last 3-4 months depending on climate before needing replenishment. Check them weekly to see if you have caught any QFF.
• September onwards: the temperature at sunset was monitored. QFF mate at sunset when it is 16degC or warmer. When this temperature occurs, it is an indicator that QFF may soon emerge and lay eggs.
• As soon as flowers on fruit trees were pollinated by bees and other pollinators, the trees were netted with 2mm x 2mm insect netting which was weighted down around the hem. This included all citrus. All vegetables were netted when planted as most are self-fertile, and weighted down around the hem. (It may be necessary to hand pollinate eggplant, chillies and capsicums).
• Any fallen fruit was microwaved and disposed of in the waste bin twice weekly. None was put in the compost!

At Sustainable Macleod, we favour netting as our primary strategy. If QFF cannot get to the produce then they cannot harm it. We use the lures and traps as back-up and as indicators of whether or not QFF is actually present.

Mistakes that we made early-on included: not weighing down the netting to prevent QFF from crawling under it; not netting early enough or not netting everything; pulling out spent plants with fruit on it, say chillies, at the end of the season, and not disposing of it straight away or exposing it in compost where QFF could then lay eggs in it; and not checking lures and traps despite our good intentions.

Starting early and being vigilant are the keys to success. You will not see any damage until you cut open ripe fruit or veggies so damage may be occurring right under your nose. Given the time and money, we expend on our edible gardens, executing a strategy to protect our produce makes sense, and we can succeed even if our neighbours are failing.

Where to obtain supplies:

• Supplies are surprisingly hard to buy locally. As a service to the community, Sustainable Macleod sells Wild May, lure bottles and netting at cost price. Go to our shop to purchase.
• Ceratraps can be bought online in bulk quantities so join together with friends to share the cost. The cheapest way to purchase is to buy 5 litres and 20 traps for around $210. Google Ceratraps and look for the best deal.
• Netting can be purchased from some nurseries, including Bulleen Art and Garden. It is typically 6 metres wide and about $5 per metre. Avoid buying packaged netting, which is too narrow to do the job.

March 2022 article

I’ve heard a number of people refer to April as the end of the Queensland fruit fly (QFF) season, presumably because their summer veggies and summer fruit have now been harvested. However this is a misunderstanding. The QFF season never ends because the QFF life cycle is a 12 month cycle. Now (April) is the time to do everything in your power to make sure that the larvae do not enter the soil and pupate ready to hatch in the spring.

The first jobs are:

• Remove all fallen fruit from the ground.
• Remove any fruit left on trees that cropped in summer.
• Remove any veggies such as tomatoes or peppers or chillis still on the bushes.
• Dispose of any of the above by cooking (baking, boiling) or microwaving, or solarising for 7 days in double black plastic bags, and then wrap anything not in plastic bags in newspaper and place all in the waste bin.
• Do not put any infested fruit, even treated fruit, in the compost as this is an ideal breeding ground.

Now turn your attention to autumn fruit. Autumnal fruits such as feijoas, guavas, and autumn raspberries are heavily infested with QFF in many gardens right now. Feijoas and guavas fall readily to the ground especially when infested. On the tree, infected guavas will look like droopy sacks and feijoas will have dark, soft patches and obvious holes. Rake out any fruit under the tree and strip any fruit that appears to have QFF and dispose of as above. With raspberries, you will need to break them open and check whether there are larvae. These will be creamy coloured and evident from their wriggling. Note that white spots inside the raspberry are not QFF but rather part of the seed. Feijoas and full size guavas are climacteric fruits, meaning they will ripen off the tree, so pick them early and ripen them indoors.

Then if you have chooks, let them loose under your fruit trees and they will scratch out any pupae and clean up larvae on the surface. Borrowing a few chooks for a day or two may even be an option!

Winter fruit such as persimmon and tamarillo need to be picked as soon as they start to colour and then ripened indoors. Citrus cannot be harvested until it is ripe as it does not ripen after picking so spray with kaolin clay (sometimes called/branded as ‘overhaul’).

Quite soon the female QFF will die, leaving the males to overwinter in warm places in your garden. These males will then mate with the females that hatch from pupae in the spring, and produce the first flush of QFF infestation around September (the second flush will be from December onwards). QFF males assemble in leks – groups of about 10 – and live through the winter in either the canopy of trees (such as lemon trees) or in trees adjacent to warm spots (such as compost heaps or chook pens). It is therefore a good idea to put Wild May traps which attract males in the canopy of trees in these areas to reduce their number. Do this from May onwards. Place them 1.2-2 metres high on the east side of the tree where it will get the weak morning sun (placing them in hot sun evaporates the liquid quickly and denatures it).

Now is the time to prepare a plan for the spring. There’s a lot of evidence from local growers about what works. Taking the following measures can result in your fruit and vegetables being completely free of QFF next season. It’s all about taking early action!

• Net all vegetables that are subject to QFF infestation at the time of planting, making sure the net is secured to the earth in some way – wood, earth, pegs etc. (Many nurseries sell wide net off the roll, which is both less expensive and better than the narrow net in packages. You can buy exactly the amount you need. 2x2mm or 1x3mm exclusion netting is suitable.)
• Net all fruit trees and tie the net to the trunk or weight it down or use net sleeves over branches of fruit or spray all fruit with kaolin clay so that they look ‘snowy’. This will have to be done 3 or 4 times throughout the season, and trees checked after heavy rain. Spray the fruit on all sides.
• Prune your fruit trees so that you can easily reach all fruit and easily net or spray.
• Net all berries as it is too difficult to remove kaolin clay from them (kaolin washes off easily from larger fruit).
• Net any indigenous edible fruit bushes.
• Put out protein baits which attract both males and females but don’t rely on these to do the job or to tell you if there is QFF about – take action earlier (as above) so that when they do arrive, it won’t matter. Put these out in August. I recommend Cera-traps which last a whole season. Making your own protein baits is a possibility but as they need to be changed every 5 -7 days, and most people don’t do this, I think the cost of Cera-traps is worth it.
• Be wary of relying on online advice from well meaning people about when QFF is about in your area. There are many reasons that QFF may be in one person’s garden but not another’s. Much better to take action before there is any possibility of QFF being around.

In summary:

• Clean up all fruit now (April).
• Put out Wild May in May and continue through the year.
• Put out protein baits in August and continue through the year.
• Net all seedlings at time of planting, especially summer seedlings.
• Net fruit trees or use net sleeves to cover fruiting branches or spray with kaolin clay.