UPFRONT discuss
Many readers of WA Grower, will be acutely aware that, in certain regions, vegetable growing and biting flies (stable fly) go hand in hand. For many decades vegetable growers and animal owners have suffered the devasting effects of this serious pest.
Words Mick Emmanuel, Stable Fly Control Officer, Shire of Gingin
IN some areas the grazing industry has experienced significant financial losses as a direct consequence of stable fly infestations. More tragically, graziers, and other animal owners have witnessed the terrible suffering their animals have endured.
The problem is impossible to ignore. Animals, people and businesses continue to suffer in many regions around WA. The question is, why has it continued for so long and what, if anything, is being done to bring the stable fly under control? Many people wrongly believe that nothing can be done. It is often stated, “either get used to them or move; stable flies are here to stay”.
Nothing could be further from the truth. Stable fly breeding can be brought under control. If, however, we mistakenly believe that it is impossible to control the fly, then the problem will persist, unabated. By changing our thinking and practices, stable fly breeding has been significantly reduced in the Shire of Gingin.
Importantly, these changes have realised benefits to the vegetable growers by way of savings in water usage, power and chemical costs.
The benefits to the community, animal welfare and the grazing industry have also been significant.
The Shire of Gingin Experience
The Shire of Gingin has, for nearly a decade, dedicated a part time officer (Stable Fly Control Officer) to work closely with vegetable growers, graziers and the general community. In recent years Stable Fly Control Officer, Mr Geoff Slater (Geoff ), working very closely with the T & C Do & Son operation conducted numerous experiments on the Caraban Road property, Woodridge. Mr Ali Al-Boraich, farm manager, contributed significantly to these experiments and was, and still is, instrumental in its success. This work sought to understand if it was possible to stop the stable fly breeding cycle (egg, larvae, pupae and adult fly).
Their work dove-tailed into that which Doctor David Cook (DPIRD) had been conducting over many years. Doctor Cook, of course, is very well known to those in the vegetable growing industry. His scientific contribution to this subject is world known and extremely important to the work we do on the ground here in Gingin. For that reason, I acknowledge his contribution with tremendous respect. His dedication to the scourge of stable fly has spanned more than 30 years, and we are indebted to his unmitigated passion to find a solution.
The experiments conducted on the Caraban Road property were game changing. Armed with the knowledge provided by Doctor Cook, it was known that stable fly, at optimum temperatures (25–35ºC) will complete their breeding cycle within 14 days. It is also known that temperature and moisture are inextricably linked to the fly’s breeding cycle. Most importantly, moisture is essential for the process. The fly larvae cannot survive in dry vegetable/manure matter. Simply put, to remove the moisture is to kill the larvae. Their experiments further reinforced the work of Doctor Cook in, irrefutably, supporting earlier findings that up to 90 per cent of the breeding occurs in the wheel tracks/ruts.
What is a wheel rut? The wheel rut I am referring to are those tracks caused by the tractors entering the vegetable beds for prepping, planting, spraying and later when harvesting the crops. The harvested (discarded) vegetable matter will, as a natural consequence of this activity, be pressed into the soil (under the tractor wheels). This is where moisture is trapped in the rotting vegetable matter and the flies lay their eggs. It is the perfect environment for stable fly larvae/pupae to thrive. Of course, this is where most of the breeding occurs.
Knowing this, Geoff proposed that the tractor wheel tracks/ruts be lifted by way of twin tynes (see picture) following the harvest. The water must then be turned off. The discarded vegetable matter is left on the surface to dry out. Leaving the discarded vegetable matter on the surface ensures that topsoil erosion is mitigated throughout the drying period.
This simple process has many very important positive aspects. Firstly, it stops the stable fly breeding cycle. It also means less water, electricity and chemical are used. In short, the vegetable grower, in adopting this process, can realise a triple cost positive approach whilst effectively controlling stable fly breeding. A win-win for all stakeholders.
In what must be a world-wide first in insect mitigation, this process offers a cost-positive solution to a devastating problem. Also, on a positive note, vegetable growers do not have to make significant changes to their existing practices. Where this method has been adopted by growers, stable fly numbers have been so significantly reduced that long suffering neighbours have reported life changing improvements.
Manure management
It might come as surprising to some readers that manure (chicken, pig and other) if properly managed, can be used effectively and not breed stable fly. Having stated that, it remains a high-risk material and subject to legal constraints in some local government jurisdictions. For that reason, I direct the reader to the Stable Fly Management Plan, 2019.
Some of our most expansive vegetable growing operations use chicken manure very effectively. The following are some important criteria adopted and applied by these operators to ensure there is no risk of stable fly breeding:
• Manures are never stockpiled. The material is spread out at a predetermined rate per hectare immediately following delivery.
• Operational planning logistics ensure that manures arrive on an agreed date to fit with farm operations.
• Limestone road base is used as a pad for the manure to be placed on. This mitigates the risk of fly breeding where moisture from the manure leeches into the soil.
• The rate at which the manure is spread is critical. If spread too heavily, especially under irrigation, it is a perfect breeding medium for stable fly. Large lumps must also be avoided for this reason.
Manures, if mismanaged or misunderstood, can breed stable fly in catastrophic numbers.
It is for this reason that the above criteria were conceived, put into practice and evaluated. Where these have been adopted, there is no evidence of stable fly breeding in measurable numbers.
A final few words
We still have some way to go. Having stated that, more and more growers are adopting these simple changes and are realising the benefits. We will continue to work closely with our vegetable growers to improve where we can and seek even better ways of tackling this pest.
Here, in the Shire of Gingin we know that stable fly can be controlled. It is factually wrong to think or act in a way that suggests that we must learn to live with it.
The willingness to adopt fresh ideas by some of the vegetable growers in the Gingin region is commendable. Regarding stable fly control, an outstanding example of ‘best practice’ for the vegetable growing industry is described above (T & C Do and Son operation). Their work on stable fly control is not only leading the way, Mr and Mrs Do are happy for other growers to visit, observe, discuss and learn from their experience. Together with their farm manager Mr Ali Al-Boraich, the Do family are outstanding ambassadors in the vegetable industry.
The Shire of Gingin will remain steadfastly committed to tackling the scourge of the stable fly. As the resident Stable Fly Control Officer, I will continue to work closely with our local vegetable growers and all other stakeholders. It is through effective communication, problem-solving and education that we have accomplished our best results. With every success, many animals are relived of their suffering. In this knowledge, I derive my greatest motivation to succeed. I invite you to join me in this quest.