In November 2019, Penny Grose wrote an article on Queensland fruit fly for this website. In February 2020, Bron Koll, Queensland fruit fly coordinator for Yarra Valley Agribusiness, added her comments. In March 2020, Even Gellert added his thoughts. Ditto Pam Jenkins in January 2021 and Paul Gale-Baker in March 2021. All five contributions are below in reverse chronological order.
The National Fruit Fly Council provides a wide range of advice.
Paul Gale-Baker – kaolin clay (March 2021)
Kaolin clay, best known by home gardeners as a spray to control gall wasp, has apparently proved to be successful in trials as a preventative for Queensland Fruit Fly infestation. Trials are ongoing.
Kaolin clay is an organically registered product, described as a ‘light spray oil emulsion’. It is made of clay (as the name suggests) and, when sprayed, provides a light, white covering for fruit, stems and leaves. It is effective on citrus, stone fruits, pome fruits (including apples) and tomatoes. The Department of Primary Industry has reported that sting marks on apples were reduced by 92% and that there were no larvae or maggots in the fruit in a trial run at Bathurst, NSW.
The spray is also ‘soft’ on beneficial insects. It deters grasshoppers, codling moth, leafrollers, mites, thrips, some moths and Plum curculio, as well as gall wasp. These insects are deterred from landing, feeding and egg laying by the unsuitable surface that the kaolin clay film creates. Note that it needs to be produced commercially to refine it to the correct particulate size as pure kaolin clay will kill trees.
To be effective, trees need to be fully sprayed and research thus far suggests spraying early in the season is essential. Spraying needs to be done three times, a week apart each time, and will not work unless all three sprays take place. To be effective, spraying should be to the point where the solution drips from the leaves. Rain will not wash it off until late in the season when its job will have been done.
Additionally, strong, healthy trees get the best results. This requires good soil and water management so that the trees are well fed and can draw on plenty of moisture. This in turn encourages the presence of beneficial insects and deters attacks by non-beneficial ones.
My experience is that I may have inadvertently protected the fruit on my 6 citrus trees by spraying kaolin clay from October to December to deter gall wasp. While many of my friends have citrus (particularly lemon trees) that have been devastated by Queensland Fruit Fly, my trees are completely free of this pest.
In summary, kaolin clay looks like a very promising treatment for Queensland Fruit Fly. I will be using it from August onwards but I will also be combining it with other methods including exclusion netting, pheromone and protein traps, and biodiverse planting under all my fruit trees to encourage beneficial insect predators.
Newsletter reader suggested links (January 2021)
Richard Rowe has published some guidance on the Edendale website. At the bottom of that page, is two videos of a webinar that Richard, Bronwyn Koll (QFF co-ordinator for Yarra Valley) and others ran last year.
Pam Jenkins (January 2021)
I suggest that you read this report from Horticulture Innovation Australia. It looks like there may be some hope in integrating kaolin with exclusion netting especially for the home gardener … Kaolin looks like a great alternative to the previous regimes of cover spraying with toxic chemicals. It is going to affect pest insects that inject eggs, suck or chew on fruit and, so far, my reading suggests that it has little impact on beneficial insects and bees unless it is sprayed directly on to them. It has the added bonus of reflecting sunlight so helps prevent sunburn and slows evaporation from leaves in really hot weather. I also read that it doesn’t affect photosynthesis but I haven’t had it on leaves long enough to confirm that for myself.
Evan Gellert (March 2020)
Evan Gellert is from Eltham, where his property backs on to the Diamond Creek
Queensland fruit fly (QFF) (Bactrocera tryoni) can infest nearly all fruits and fruiting vegetables, including solanums and cucurbits. Our Eltham neighbours have been devastated by the infestations to their stonefruit this summer. Separated by about 100 metres from them, our stonefruit escaped but our tomatoes are now being infested in March. The larvae and less than 2mm long when they first hatch, and then grow to 5-9mm long. Look for these on the move inside infested fruit. Adult flies are 5-8mm long, generally brown, with yellow shoulder pads and a yellow patch on the mid lower back.
QFF was recognised as being on the rise in Nillumbik from January this year. But this was not the first time: a co-volunteer with the Heritage Fruits Society told me some years ago that QFF had been here. The Nillumbik Council website has some advice of the subject, including a downloadable fruit fly guide. If your fruit has been infested by the small larvae this season, I suggest you download this guide.
QFF is found throughout eastern Australia, from Cape York to Victoria. They prefer to gather in dark spaces, probably due to their forest origins. Creek lines have been suggested as a likely transmission route through suburbia. They rarely fly across open grassland. Where I live backs onto the Diamond Creek. I wonder whether there are notable differences between the ridge-lines and creek-lines for infestations in Eltham. The flies are reported to be repelled by white surfaces which might explain their low incidence in plastic greenhouses. They mate for only around 30 minutes at dusk.
Why did we escape infestations to our apricots and nectarines only 100 metres from our neighbour when QFF is known to circulate over 500 metres (but rarely more than 1 km)? It could have been our insect net which we use as fruit tree netting. The mesh size of 1 x 3mm should exclude the flies, and the white colour might deter them. I have finally netted our tomatoes late in March and seen the QFF inside trying to get out. I’ve made a calendar note for earlier next year to erect netting over tomatoes. Infested fruit can’t be just composted, or the cycle continues.
Why have the flies been much more active here this year? We can only guess. Perhaps we have had a series of milder winters which otherwise keep numbers in check. Or perhaps other random environmental drivers have favoured their breeding.
Bron Koll (February 2020)
Bron Koll is Queensland fruit fly coordinator for Yarra Valley Agribusiness.
Fantastic to read that so much information has been retained and passed on to those who need it. Thank you!
I am too saddened by the discouraging of sharing produce. We are only asking that the utmost care is taken. If you can’t be certain that the fruit is QFF free, then take precautions like cooking or preparing the fruit before transferring it. If receiving fruit, have a little biosecurity plan of your own. Accept the fruit into the kitchen (not the yard) and prepare the fruit for consumption. Freeze or boil the scraps. Take care that nothing goes into your production area that is doubtful. It can be done!
My additional QFF management comments are as follows:
1. It’s a community effort – areawide management is required for QFF control to be effective, everyone needs to pitch in (including public land managers).
2. Prevention is one massive control option, but if QFF is around, trapping (monitoring), baiting and hygiene are all required in unison. One has to use a multi-pronged approach.
Bron’s contact details are 0490 381999, email@example.com.
Penny Grose (November 2019)
Penny Grose is from Rosanna and co-convenor of Transition Warringal.
Early in 2019, I learned of cases of Queensland Fruit Fly in Brunswick West and Viewbank, so became more interested in the topic.
I recently learned more about preventing and managing it at an ORICoop workshop (ORICoop is a new cooperative working to support organic and regenerative farming across Australia through farm management and investment in organic farms.)
At the workshop, I learned that QFF has spread across a significant area of Victoria, especially in home gardens, as a result of lack of awareness, partly due to de-funding of public services in recent decades. A few years ago, there was an increase in cases in the Greater Sunraysia Pest Free Area, which has been managed. I gather that it’s currently throughout Wodonga, Shepparton, Bendigo and Seymour. There was a case in the (upper) Yarra Valley that has been managed and engagement with home gardeners is continuing there. The QFF Regional Coordinator in the (upper) Yarra Valley, who co-presented the workshop, is Bronwyn Koll. You can contact Bronwyn by email.
There is currently government funding ($5,000 grants) for QFF community education in Victorian municipalities, except the Melbourne metropolitan ones. Communities are presenting workshops, creating videos and bulk buying traps, bait and netting to supply at cost to home gardeners.
The take home message was that every home grower of fruit trees (as well as susceptible veggie fruits like tomatoes) should watch out for it, use monitoring traps and be ready to manage it with traps, baiting and exclusion (netting).
We should avoid transporting fruit between regions. We should be wary of sharing home grown fruit unless we are sure the grower is actively monitoring and managing the risk. (How sad that sharing is being discouraged!)
QFF can travel kilometres under their own steam. Insects are also carried on the wind.
There are lots of trap and bait types. An organic bait is EcoNaturalure (active ingredient spinosad, an insecticide extracted from bacteria).
All fruit trees should be pruned to convenient harvesting height to ensure that every piece of fruit is harvested, to eat or destroy as appropriate. All fallen fruit should be collected.
Any affected fruit should be boiled or frozen to kill eggs and larvae.
Much of the Agriculture Victoria information is a bit dense, so not very helpful to the home grower. More accessible information resources are the regional home gardener education materials, for example: Great Sunraysia Pest Free Area and Fruit Fly Yarra Valley.
I read the Grow Great Fruit newsletter from the farm formerly known as Mt Alexander Fruit Gardens. They provided the links below:
- Agriculture Victoria’s Managing Fruit Fly in the Home Garden.
- An e-book: What’s Bugging My Fruit.
- Mount Alexander Fruit Fly Facebook Group.
- Bendigo Region Fruit Fly Facebook Group.
- The Victorian Government’s Fruit Fly surveillance outbreak monitoring.
- The Australian Handbook for the Identification of Fruit Flies. This is a fairly high-level document published by Plant Health Australia that is a compilation of diagnostic information for 65 fruit fly species.
- The Harcourt Valley Fruit Fly Regional Action Plan.
- The Harcourt Valley QFF Emergency Outbreak Plan.