New research to focus on weevil control

Eradicating native weevils from export apples should become easier, as the Department of Agriculture and Food (DAFWA) embarks on new research.

Researchers led by YongLin Ren, who is based at Murdoch University, are using ethyl formate to disinfest fruit and make sure that hitch-hiking eucalyptus weevils cannot survive — a current barrier to export apple sales.

“Vaporised ethyl formate was delivered into cool rooms, ” Dr Ren said.

“We are finding the right concentration and duration at a temperature range of 5 to 13C to give 100 per cent mortality of adult weevils without affecting the shelf-life and quality of the apples.”

After commercial trials of ethyl formate on 2000 tonnes of Pink Lady apples in Manjimup cool rooms in 2010, about 300 tonnes of Pink Lady apples were exported to the United Kingdom — a market that lists eucalyptus weevil as a quarantine pest.

The eucalyptus weevil is not a direct pest of apples but uses them as an ‘over-wintering site’, making it a quarantine pest only, Dr Ren said.

The eucalyptus weevil is found in blue gum plantations, but it is not a major economic problem in Australia, due in part to its natural enemies.

However, the weevil has become a pest in some overseas plantations, which has led to the blocking of apple exports to those countries free of the insect.

Dr Ren said while the research was not yet complete, fumigation had been effective and left negligible residues when the apples were aerated.

He said ethyl formate had great potential for pre-shipment treatment of export apples.

Ethyl formate is already registered as a disinfestation control for some horticultural commodities, but not in the exact way used in the recent trials.

This use is considerably cheaper than other fumigants used commercially, some of which cause phytotoxic reactions and reduce fruit shelf-life.

The research will be completed in 2012 after further trials.