Pitfall traps are best for pea leaf weevil
By Sue Roesler The Prairie Star
“The pea leaf weevil has been a traditional pest for many years, and there is a lot of these pests in Canada,” says Gadi V.P. Reddy, entomologist of Montana State University’s Western Triangle Agricultural Research Center (WTARC). “The pea leaf weevil spread across the pulse growing regions in 2012, increasing problems caused by the pest.”
Reddy spoke at WTARC field days about his pheromone research project. Reddy has grant funding under the Montana Specialty Block Grant program, in cooperation with the Montana Department of Agriculture and USDA-National Institute of Food and Agriculture (NIFA), for the pea leaf weevil pheromone project to attract the pea leaf weevil.
There are two generations of pea leaf weevil per year, but the second generation of adults don’t cause damage like the first generation. During winter, the weevil hibernates under debris leaves and emerges in the spring, usually around May. When the pest emerges in spring, the adults feed on pollen and nectar on leaves; then they mate and the females lay eggs on the seedlings of peas and lentils that emerge as larvae. The larvae or grubs burrow deep in the soil and feed on roots and root nodules, causing damage. Plants fix less or no nitrogen when the roots are damaged, and sometimes the plant itself dies.
Reddy experimented using baited aggregation pheromone traps in the field to help monitor and mass trap weevil populations. He found that the pitfall traps worked the best at catching pea leaf weevils. These traps are a container that is sunk into the ground so that its rim is flush with the soil surface. Insects simply fall into the trap. Reddy used a liquid aggregation pheromone to lure them.
Another pheromone lure type is a bubble wrap, placed in pea or lentil fields.
In these traps, growers use a small quantity of soap or detergent water so that the trapped weevil gets killed.
“We found a lot of pea leaf weevils in our pheromone traps in 2016. Next summer, we will determine how many pheromone-baited traps we need per acre to trap the weevils,” Reddy says.
In addition, WTARC will be developing biodegradable pheromone lures so that growers won’t have to take them out of the field after each season.
Reddy is also looking at bio-based insecticides to control pea leaf weevils.