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Cereal aphids

Agronomist, Mick Duncan (Northern Agriculture), has reported finding aphids in several wheat and barley crops around Tamworth, in the North West Slopes and Plains district of New South Wales. High numbers of aphids could be easily found on the lower stems of plants, however Mick says the plants are not moisture stressed and the aphids do not appear to be impacting growth at this stage. Some aphid ‘mummies’ were also present, indicating the presence of small aphid parasitic wasps.

The two main aphid species found in cereal crops are the oat aphid (Rhopalosiphum padi) and the corn aphid (Rhopalosiphum maidis). Although oat aphids are mostly found on oats and wheat, and corn aphids are more common on barley, both species may attack all cereals. For both species, a commonly used threshold is to consider control when there are 10-20 aphids on 50% of tillers. However, the impact of aphids on winter cereals (yield and quality) is the result of a complex relationship that involves the timing of infestation, aphid density, where on the plant the aphids feed and crop physiology at the time of infestation. For further information on cereal aphids, refer to PestFacts Issue No. 8.

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