BIOLOGICAL control of major insect pests such as western flower thrips is now possible for the Western Australian horticultural industry as new beneficial insects become available.
Sending ‘good bugs’ in to battle the pests has been part of a Department of Agriculture and Food project for more than four years and western flower thrips is a prime target.
Senior research officer Sonya Broughton said integrated pest management using combinations of weapons was essential, as many pests were developing resistance to new pesticides in as little as three years.
“Insecticides never achieve total kill,” Dr Broughton said. “Some insects always escape, and sprays wipe out the beneficial insects in the environment as well as the pests. Using a mix of tactics can save money as well as preserve the effectiveness of sprays for as long as possible.”
A new weapon for WA producers is a native bug called Orius armatus. Orius is being successfully reared and distributed with several other beneficial insects by Manchil IPM Services at Muchea.
Initial attempts to rear it in the 1990s failed, but success was achieved using a new system developed by Lachlan Chilman at Manchil IPM about two years ago.
Dr Broughton said western flower thrip was found in WA in 1993 and had since spread to all states except the Northern Territory.
“It attacks more than 200 different horticultural species including lettuce and other vegetables, brassicas, strawberries, flowers, stonefruit and pomefruit,” she said.
“In WA, it has spread from the Perth area to Carnarvon, Manjimup and Donnybrook.
“Western flower thrips also carries tomato spotted wilt virus which can devastate some crops. In 2003, more than 90 per cent of lettuce crops at Carabooda were lost when infected by the virus.”
Dr Broughton said western flower thrips was difficult to control with pesticides as different lifecycle stages hid and fed in foliage and flowers, soil and leaf litter. It also developed resistance to sprays very quickly.
“Orius was released commercially in September and is often combined with three other beneficial predators that prey on these different lifecycle stages,” she said.
“Orius is a native species and its numbers vary in the wild. Rearing it in captivity and producing numbers sufficient to release into glasshouses has been a major achievement.”
Dr Broughton said beneficial insects took time to build up and were not the instant fix that might be achieved with blanket spraying of chemicals.
“Sometimes growers still have to use pesticides, and timing is important so that chemicals do not wipe out the good guys as well as the bad,” she said.
The main trials and commercial use of orius to date have been in glasshouses where temperature and humidity can be controlled. Further research is needed under field conditions as well as in glasshouses.
Mr Chilman estimates about 80 per cent of strawberry growers are now using the beneficial insects as part of their pest management strategies.
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