Build up of aphids is for some much worse than others

The incidence of aphids has been highly variable both among crops and regions. Northern NSW have had reports of virus symptoms in chickpea crops

Cabbage aphids on canola (Source: Phil Bowden) 

 

Where have they been reported?

Aphids appear to be one of the most consistent crop pests this spring, with reports from central and northern NSW and central and southern Victoria. However, the nature of reports differs greatly between regions.

Victoria:

Central and South Western districts:

Generally cereal crops have low numbers of aphids, although there has been an obvious difference between crops that used insecticide seed treatments (having low aphid numbers) and those that did not (having higher aphid numbers). These flow-on effects of seed treatments into spring are related to the size of overwintering colonies, which then build up in early spring. In paddocks where aphid populations are relatively high, there is evidence of parasitoid activity (aphid mummies) as well as hoverfly larvae.

Canola crops across the region generally have low numbers of winged aphids on the edges of crops at present. However, there are few established colonies. In these crops, hoverfly adults have been reported. The same scenario for aphids has been observed in faba bean crops, although brown lacewing adults and parasitoids are the most common beneficials reported.

NSW:

Central West Slopes & Plains:

Bluegreen aphids (Acyrthosiphon kondoi) are building up within lucerne crops, as well as on under-sown clover pastures around Condobolin. This comes after cereal aphids have built up and have now declined within the area.

North West Slopes & Plains:

Reports of virus symptoms have been coming from chickpea growers in the Northern region of NSW. These reports, mainly coming from late-sown chickpea crops, correspond with the large influxes of winged aphids (mostly bluegreen and pea aphids (Acyrthosiphon pisum)) that were recorded throughout August.

About aphids

Spring is the time when aphids are most commonly seen, particularly on the upper parts of plants and around the growth points. Where present, natural enemies, including hoverfly larva, lacewings, ladybird beetles and parasitoids, can keep small to moderate populations of bluegreen aphids under control during spring.

For more information about aphids, including their occurrence, lifecycle, behaviour and management strategies, go to bluegreen aphid and pea aphid within the new PestNote series.

Our advice

Growers should remain alert to the risk of aphids causing damage and spreading virus, particularly in late sown crops. Monitor 3-5 locations in the crop and examine 5 plants at each location. Also, watch out for evidence of aphid parasitism (aphid ‘mummies’) and monitor their changing numbers over time. Parasitoids play an important role in suppressing spring populations of aphids and other pests.

 

Source of field reports of aphids

Frank Henry – Regional Research Agronomist, DEDJTR (Victorian Wimmera)

Neil Hives – IPM consultant covering central, southern and western Victoria (based in Central Victoria)

Joop van Leur – Plant Pathologist, NSW DPI (NSW North West Slopes & Plains)

Olivia Wright – Agronomist, AGnVET Services (NSW Central West Slopes & Plains)