Numbers of winged aphids entering legume crops in NSW North West Slopes & Plains have rapidly increased in the past month; crops in the area should be monitored regularly.
Where have they been reported?
Over the past month, large influxes of migrant winged aphids have been recorded on yellow sticky traps at the edges of chickpea, field pea and faba bean crops. These have been observed within research stations located near Tamworth in the NSW North West Slopes & Plains district.
Double-sided yellow sticky traps have been used to monitor flights of winged aphids into crops over the season. One trap collected aphid numbers equating to over 1,500 aphids per m2 per day during the week 20th-27th August.
These aphids were predominantly bluegreen aphids (Acyrthosiphon kondoi) and pea aphids (Acyrthosiphon pisum), as well as much fewer numbers of cowpea aphids (Aphis craccivora).
In comparison, at the same location, traps catches of winged aphids during autumn influxes had not exceeded 35 aphids per m2 per day.
About aphids that attack legumes
For comprehensive information on aphids that attack legumes, including their occurrence, lifecycle, behavior and management strategies, go to bluegreen aphid, cowpea aphid, pea aphid and spotted alfalfa aphid within the new PestNote series.
Yellow sticky traps are a good indicator of relative numbers of incoming aphids over time.
They are a particularly useful indicator in autumn and late winter/early spring, when winged aphids generally arrive in crops.
As is the case around Tamworth at the moment, high numbers of migrating aphids during spring have the potential to impact on the development of later sown crops such as chickpeas.
Yellow sticky traps are coloured specifically for catching a number of winged insects including aphids.
They are designed to be long lasting and weatherproof, and the gridded squares help counts of relative numbers over time, which is particularly useful in early spring.
Traps can be hung on a plant within the crop, or from fence wires nearby the edge of crops.
Unfortunately, yellow sticky traps are limited to monitoring winged aphids and do not represent numbers of established aphids within the crop.
Ideally, monitoring for aphids and their parasitoids should commence in mid winter and continue throughout spring.
Aphid populations can build up rapidly with increasing temperatures.
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 often play an important role in suppressing spring populations.
Crops that are not moisture stressed have a greater ability to compensate for aphid damage and will generally be able to tolerate far higher infestations than moisture stressed plants before a yield loss occurs.
Source of field reports
Joop van Leur – Plant Pathologist, NSW DPI (NSW North West Slopes & Plains)
Michelle Yates – Entomologist, NSW DPI (NSW North West Slopes & Plains)