Managing Biting Fly in Vegetable Crop Residues
Stablefly is a serious economic and social pest worldwide, affecting livestock productivity and human lifestyle. This fly is a major pest along the Swan Coastal Plain in Western Australia developing largely from vegetable crop residues left after harvest. This area produces most of WA’s vegetables, of which >50% are exported. Both male and female flies regularly blood feed and as few as 20 stablefly/animal cause distress and measurable losses.
Typically one to several hundred stablefly develop/1 m2 of crop residues left to rot untreated (1-3 million flies/ha). Removing crop residues at harvest would prevent stablefly development, but this is problematic and costly, and would deplete soil organic matter. Hence this project examined techniques to accelerate the breakdown of crop residues left in situ after harvest to minimise stablefly breeding.
Physical, cultural, chemical and biological options were tested in 13 field trials and other methodologies. These demonstrated that high speed mulching residues and turning overhead irrigation off after harvest reduced stablefly by up to 85%. Stablefly numbers were also reduced by adding to the residues (in decreasing order of effectiveness) (i) calcium cyanamide (CaCN) fertiliser @ 0.5t/ha), (ii) single species of entomopathogenic fungi, (iii) lime or lime sand (2.5t/ha), or (iv) organic matter bio-accelerants. A predatory beetle of stablefly eggs was found in celery residues and shows promise for biological control.