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Beneficial insects

Beneficial insects have been observed in high numbers in many crops this spring. Researcher, Dr Aston Arthur (The University of Melbourne), has found large populations of ladybird beetles, lacewings and aphid parasitic wasps in several canola crops near Dookie, in the Northern Country district of Victoria. Aston says aphid populations within these crops are particularly low this season. We have also received reports of high levels of aphid mortality caused by parasitic wasps from various canola and pulse crops across the Northern Country district of Victoria. Grower, Bronwyn Hunt, has reported finding very high numbers of several beneficial insects when sweep netting crops west of Kerang, in the Mallee district of Victoria. Bronwyn says lacewings, damsel bugs and various parasitic wasps have been observed. Predatory shield bugs have also recently been identified from sweep net samples taken in canola crops west of Ouyen, in the Victorian Mallee.

Agronomist, Peter Watt (Elders), has observed high numbers of hoverflies when sweeping canola crops near Cowra, in the Central Tablelands district of New South Wales. Peter says hoverfly larvae have been found in numbers ranging from 5-20 per m2. Other beneficial insects including lacewings and ladybird beetles are also present within the crops. Peter says these beneficial insects have contributed to a significant reduction in aphid pest populations this year.

Growers should consider numbers of beneficial insects before deciding on control strategies, particularly when dealing with low to moderate numbers of aphids and caterpillar pests. For further information on beneficial insects likely to be encountered in broadacre crops and pastures, refer to PestFacts Issue No. 8 or view the GRDC Back Pocket Guide – Beneficial Insects.

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