PestFacts August (no. 2) 2021
Get ready for pea weevil with monitoring and spraying
In response to recent warm weather, the SARDI pea weevil model predicts adults of the pea weevil (Bruchus pisorum) commenced their invasion of pea crops in most South Australian regions on 19 August 2021.
Start monitoring immediately
Sweep-net monitor at 5–7 day intervals around the edge of pea crops, at about 2 metres into the crop. Concentrate near trees and other hibernation sites (sheds, etc). Check the net every 25 sweeps. The spray threshold is at least 2 adults per 25 sweeps, averaged over 5 to 10 sampling sites.
To effectively control pea weevil, adults must be killed before they lay eggs. This means spray timing is essential to achieve good pea weevil control.
We estimate that egg-laying will commence around 1 September 2021 at which time about 75% or more of the weevil population is likely to have emerged and moved into crops. This estimate is based on the predicted:
- invasion start date of 19 August 2021
- maximum temperatures in the coming days.
If the spray threshold is reached, spray podding pea crops around 1 September 2021. For later crops, where pods won’t form until after this date, spray as the first flowers wither.
Border spraying
If thresholds are exceeded, a 20–40 metre width border spray is the most cost-effective way to control pea weevil, as adults will invade from the border.
However, if sweep-net monitoring reveals densities of native budworm (Helicoverpa punctigera) exceeding the threshold, then one whole-crop spray will control both pests. To calculate the native budworm threshold, go to native budworm PestNote.
After pea weevil treatment, monitoring and threshold-based treatment for native budworm should continue as normal.
Recent reports indicate that native budworm has only been reported at Mitchville on early sown peas. The trapping network is being set up. Find out more in PestFacts Issue 6.
Other management: early harvest
Good pea weevil management includes harvesting pea crops as early as seasonal conditions permit.
Early harvesting ensures that the pea weevil infestation is still immature and adults aren’t present to disperse during harvest. This will minimise pod and seed shatter, damage from pea weevil feeding, and the risk of grain rejection at delivery.
It also provides the long-term benefit of reducing the abundance of pea weevil in the same location next year.
