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 28 August 2022.

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 start around 11 September 2022 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:

• arrival date of 28 August 2022
• predicted maximum temperatures in the coming days.

If the spray threshold is reached, spray podding pea crops around 11 September 2022. 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.

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 remains immature with no adults present to disperse during harvest. This minimises pod and seed shatter, damage from pea weevil feeding, and the risk of grain rejection at delivery.

Treating early provides long-term benefits and the reduction in abundance of pea weevil in the same location next year.