Fruit fly poses no easy answers

As one of the identities at the coal face of finding the best alternative to controlling Queensland fruit fly, Dr Lindhout’s role has taken on a greater urgency as the release of the review of dimethoate and fenthion looms.

The situation has left growers asking what they will do if the chemicals are eventually withdrawn from registration.

The answers are not clear cut.

At the National Low Chill Stonefruit Conference in Ballina this year, growers heard from the Industry and Investment New South Wales researcher who has focused her attention on improving market access opportunities for Australian-grown fruit that are hosts of fruit fly.

Dr Lindhout said there were a number of industries now looking to researchers and scientists for solutions.

“The magic bullet approach is generally having a new chemical to spray and unless chemical companies have got something in the pipeline and they are keeping it really quiet, it’s not as likely,” she said.

Part of Dr Lindhout’s presentation at the conference looked at the remaining methods of fruit fly treatment (baits, male annihilation technology and lures) if the major chemicals were no longer an option.

Some of the more novel approaches suggested included kaolin clays which have shown to be effective in some overseas cropping systems, and ultra-pure mineral oils, which are under investigation by Andrew Beattie and his team at the University of Western Sydney.

Both treatments have had limited testing and data collection for Australian crops.

According to Dr Lindhout, post-harvest treatments are the easiest to deal with but of course, if there is no suitable fruit in the first place, then it is useless.

No treatment provides 100 per cent control of the pest, however a systems approach which utilises multiple fronts may be a viable option for growers.

Dr Lindhout gave an example of a systems approach for a stone fruit crop which would include monitoring (lures); management (baits, male annihilation technology, chemicals, oils); postharvest processing (culled fruit); postharvest treatment (cold storage); and verification (inspection).

Dr Lindhout said one of the concepts growers may struggle with is that a systems approach is a long term plan and may need changes in farm management.

In her work on fruit fly treatment alternatives, Dr Lindhout has encountered varying degrees of grower concern.

“I think it’s a bit mixed, depending on the individual. There are some that are saying, if you take this away from us, I’m walking away, I’ve got no alternative,” she said.

“Others are not too worried about it, they are thinking it won’t really happen or they say, they can’t take it away if there is no alternative.

“Then others are saying we’ve got a real problem here, we need to do something about it, we need to put money put into it and start developing things now, and being really proactive about it.”

Dr Lindhout said she was excited by a meeting taking place in Brisbane this month between horticulture researchers to collaborate information.

Within the fruit fly control methods are also two forms of biological control used worldwide.

According to Industry and Investment NSW, one form is the sterile insect technique (SIT), which involves releasing sterile fruit flies to flood the wild fruit fly population, minimising the possibility of wild fruit flies mating and producing fertile eggs.

The other, is the use of parasitoids (wasps) that lay their eggs in the eggs, larvae or pupae of the fruit fly, and instead of a fruit fly developing and emerging, a wasp emerges to continue the cycle again.

In Australia, the SIT has been used for many years to control outbreaks of the Queensland fruit fly in pest free areas, particularly those encompassing some of our most valuable horticultural production areas in New South Wales, South Australia and Victoria.

Endemic parasitoids are now being studied in Australia for their use in augmentative release programs, and have already been used in areas of Queensland to control the Queensland fruit fly.

Both of these techniques can be incorporated in a systems approach and aid in reducing fruit fly populations pre-harvest.