Researchers based at New South Wales Agriculture’s Yanco Agricultural Institute (YAI) are busy staying one step ahead of a tiny exotic lettuce aphid that has the potential to bring the Australian lettuce industry to its knees if the pest finds its way to Australia.

Lettuce aphid (Nasonvia ribisnigri) has devastated the New Zealand industry where lettuce growers are ploughing paddocks of lettuce back into the ground, prompting a team of NSW Agriculture researchers at the National Vegetable Industry Centre, Yanco, to develop strategies for Australian lettuce industry to combat the aphid.

“Aphids are not new to the Australian lettuce industry, however the Nasonvia aphid is very different to other aphids because of its nature to colonise the centre of the lettuce, making it very difficult to control with foliar insecticides,” NSW Agriculture technical specialist in vegetables, Dr Sandra McDougall, said.

“Another obstacle is that Nasonvia aphid is also known to have resistance to many of the insecticides registered for use on lettuce in Australia.”

Dr McDougall’s team is certain insecticides alone will not be the answer to controlling the pest in Australia and are now looking at new ways to control the aphid.

Integrated Pest Management (IPM) strategies and new foliar and soil drench insecticides are being trialled by Dr McDougall and NSW Agriculture technical officer, Andrew Creek.

“Soil drench insecticides differ from foliar insecticides and are applied to the soil before sowing and therefore before the aphid attacks,” Dr McDougall said.

“Soil drench also has the advantage of being taken up by the roots systematically, controlling the aphids deep inside the heart of the lettuce where foliar insecticides (applied to leaves of lettuce) cannot reach.”

NSW Agriculture technical officer, Andrew Creek, said results from initial soil drench trials were impressive, with a few providing up to six weeks protection from aphid attacks.

“We still need to determine which application rates will give good control while having minimal impact on beneficial insects,” Mr Creek said.

“Preserving beneficial insects in any cropping systems, especially vegetables, is the key to a successful Integrated Pest Management system.”

More information on lettuce insecticide trials at www.agric.nsw.gov.au/reader/veg-lettuce