WA growers warned on seedling insect pests

29 May, 2012 01:29 PM

WEST Australian graingrowers are being encouraged to inspect germinating and newly-establishing crops for damaging insect pests in order to make accurate and effective insect control decisions.

Department of Agriculture and Food senior technical officer Peter Mangano said some early germinating canola crops in the south coastal and northern agricultural areas were currently being attacked by mites and small caterpillars.

“The best way to inspect crops for pests is to be frequently looking for visual symptoms such as chewed leaves, or yellowing and distortion of leaves,” Mr Mangano said.

“Considering some damaging insect pests are difficult to find because they hide beneath the soil or under stubble residue, pest assessment based on symptoms of damage is an effective method for pest monitoring.

“For example, the pest most likely to be responsible for seedling plants being chewed off at ground level leaving “stumps” is cutworm. While webworm is often the cause of portions of grass and cereal leaves protruding from holes in the ground.”

Underground damage can be identified by assessing above-ground symptoms such as stunted pale and dying leaves which indicates that pests could be chewing on developing root systems.

“Mites are the likely culprit when leaves have a silver discolouration or a distorted shape; while lucerne flea feed on the underside of leaves creating a transparent ‘window’ appearance,” he said.

Mr Mangano recommended growers use a combination of crop monitoring techniques, including a simple visual assessment such as a close inspection of tiny insects on seedlings and the soil with a hand magnifying lens. Using a shovel and soil sieve will help isolate below ground pests for easier identification.

“Accurate identification of insect pests enables the most suitable control methods to be applied preventing continued damage, the possible application of the wrong insecticide or having to re-sow badly damaged paddocks,” he said.

“Effective management also takes into account paddock history, including previous levels of beneficial and pest insects.”

Mr Mangano said smart pest management decisions could only be made following the correct identification of pest insects.

“This can be done through checking weekly updates of pests reported to be attacking crops via the PestFax newsletter which growers can subscribe to by sending details to pestfax@agric.wa.gov.au or by viewing it on the department website www.agric.wa.gov.au/pestfax ,” he said.

Crop Insects: The Ute Guide is a booklet available for growers and agri-business to assist with identification, monitoring and understanding of pest and beneficial insects. It contains information that is specific to WA and is available from the department or the Grains Research and Development Corporation for $10. Copies can also be obtained by mail order by phoning the department on 9368 3710.

Mr Mangano encouraged growers to use a range of pest management control options to minimise the impact of insects, and to avoid using insecticide insurance sprays simply because they were cheap and could be conveniently tank mixed with other chemical applications.



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