Managing biting fly in vegetable crop residues (VG12022)

What was it all about?

The stable or biting fly is a serious pest worldwide. It is a blood feeding fly that disrupts livestock productivity as well as affecting people in the area. In particular, the pest has become a problem along the Swan Coastal Plain in Western Australia, where it breeds in decaying vegetable residues left after harvesting.

While removing crop residues at harvest would reduce the problem, the practice is costly and would deplete soil organic matter.

This project investigated techniques to minimise stable fly breeding. Including by accelerating the breakdown of vegetable crop residues left in situ after harvest.

Researchers tested physical, cultural, chemical and biological control options in 13 field trials and 14 box trials.

Results from the trials showed…

• High speed mulching residues and turning off overhead irrigation after harvest reduced stable fly numbers by up to 85 per cent.
  
  
• Numbers were also reduced by applying treatments to the residue. Calcium cyanamide (CaCN) fertiliser was most effective, followed by a fungus that reduces insect populations, lime or lime sand and organic matter bio-accelerants.
  
  
• A predatory beetle found in celery residues shows promise for biological control.

Researchers generated a series of recommendations for growers including…

• Shorten the harvest period as much as possible
• Turn off all watering when harvesting is complete
• Use high speed mulch crop residues within three days of harvest
• Apply either an insecticide, CaCN, fungal agents or lime to mulched residues, leave undisturbed for one week then turn into soil.

These recommendations were incorporated into Vegetables WA’s Good Practice Management Guide of Manures and Vegetable Crop Residue, available from www.vegetableswa.com.au/resources, and the Stable Fly Management Plan (2013) within the Biosecurity and Agricultural Management (BAM) Act regulations, viewable at www.agric.wa.gov.au/bam/management-plans.

The team also held three grower field days, made 36 presentations to industry, local government and community forums, and developed a training manual for rangers, environmental health organisations and compliance officers under BAM.

In addition to reducing breeding of stable flies, the team also improved research into other ways of controlling the pest. Improvements were made to a Walk Through Trap for removing stable fly from livestock. They found that mass trapping of stable fly using sticky whiteboards and permanent cloth targets (treated with insecticide) could also be used to reduce numbers of flies effectively.

A stable fly colony was also established for use in the development of a genetically modified strain of the pest in future research.