New hope on Medfly frontline

Fruit West and the Department of Agriculture and Food are trialling a device that attracts Mediterranean fruit flies (Medfly) and kills them after several seconds of contact.

Magnet MED is the latest weapon under scrutiny by the fruit industry, after a decision by the Australian Pest and Veterinary Medicines Authority (APVMA) to suspend many uses of the chemical dimethoate, a defence against the pest.

Fruit West executive manager Gavin Foord said Magnet MED appeared to work well in Europe, which prompted Fruit West to test it in WA.

APVMA approved the trial in December 2011 and units were placed in two apple orchards at Karragullen and Jarrahdale on 10 January.

"Magnet MED uses deltamethrin plus powerful attractants that smell bad to humans but apparently fabulous to both male and female fruit flies," Mr Foord said.

The devices bring the pest to the poison using a 'lure and kill' technique. An advantage is that there are no chemical residues on the fruit, and little effect on beneficial insects making it attractive to organic and backyard growers.

In Spain and Italy it has been used for several years in citrus, pome fruit and stone fruit orchards.

Each device resembles a white card, 180 by 150 millimetres, hung in fruit trees at a recommended level of 75 units per hectare or one lure for each 20 to 30 trees.

The lures are being trialled only on apples this year and will remain in place until the end of the season, about June.

Weekly monitoring of Medfly numbers and damage to fruit will be assessed and compared with control areas on the same properties.

Senior department entomologist Sonya Broughton said the Karragullen and Jarrahdale apple orchards had been chosen for the trial because they were high-risk areas for Medfly, and the absence of other fruit crops.

"For many years growers have used organophosphate cover sprays to control Medfly, but dimethoate has largely been suspended and fenthion is likely to face the same fate in a few months," she said.

"There is no silver bullet to replace the traditional sprays, and a number of other tactics need to be employed as part of a systems approach. Magnet MED is just one of the new weapons we are investigating."

Dr Broughton said specific management actions would vary depending on location but were likely to involve strict orchard hygiene, sterile fruit flies in some remote areas, mass baiting and trapping, different chemicals and new devices.

Dr Broughton said the next step would be gaining commercial approval of the Magnet MED.