Pea weevils emerge in spring so growers need to check field pea crops
Pea weevils emerge from their winter hibernation (often under the bark of nearby trees) usually at a time that coincides with early flowering and podding of field peas. They are also dependant on warming cumulative temperatures. In some seasons the pea weevil beetles emerge en masse to enter crops with a spell of warm weather such as several days above 25°C. In other years with mild and cooler temperatures the pea weevil emergence is delayed or staggered over a longer time frame.
Growers are encouraged to use a sweep net to check their field pea crops regularly to determine the presence and duration of pea weevil activity.
Finding pea weevil
Districts where field peas were grown last season and where patches of the crop were left un-harvested, or on-farm stored seed was not fumigated, are likely to have the largest populations of pea weevils.
Peas grown within a 5km radius of last year’s field pea crops will be most at risk of pea weevil attack.
Commencing sweep net monitoring before the first pods begin to form is recommended. Sweep netting should be done on sunny days during the warmest part of the day (temperatures >18°C). Pea weevils are most likely to be found first along the edges of paddocks nearest to trees and/or last year’s field pea stubble. Sample for pea weevil along the crop edges within about the first two metres.
If more than one pea weevil in 100 sweeps is present then spray a synthetic pyrethroid (alpha-cypermethrin, cypermethrin, beta-cyfluthrin, beta-cypermethrin, deltamethrin, esfenvalerate, gama-cyhalothrin, lambda-cyhalothrin etc.). In large paddocks clear of trees, it is usually only necessary to spray a 60m border around the paddock because pea weevils mostly remain near the crop edges of the paddock.
Eggs on pods and larvae in pods will not be killed by insecticide so it is important to kill adults before they lay eggs.
Recommence monitoring the crop about 10-14 days after spraying and if you find more pea weevils a further spray should be applied. In some crops a whole crop spray will be needed especially if any native budworm caterpillars are also found.
For more information contact Dustin Severtson, Development Officer, Northam on +61 (0)8 9690 2160.
Article author: Dustin Severtson (DPIRD Northam).