The annual pea leaf weevil (PLW) survey that is conducted by the Alberta Insect Pest Monitoring Network was released in early December. This important tool can provide insight into PLW pressure in your region of the province. The Alberta Insect Pest Monitoring Network is a collaboration between Alberta Agriculture & Forestry staff, independent agronomists and pulse growers across the province who cooperate in providing access for monitoring and survey of adult feeding. While the maps represent observed notching in the leaves of pea and faba bean plants by the adults, the damage is done by below ground feeding on nodules by the larvae. The publication of these maps is not a forecast for the 2019 growing season, but rather a summary of where adult feeding was located.
The only tool growers currently have to suppress the damage (as control is defined as >80% reduction) is through seed treatment with a registered neonicotinoid. Thiamethoxam (CruiserTM) and Imidacloprid (Stress ShieldTM) are the actives that can provide a window of protection so that pulse seedlings and their newly-formed nodules can symbiotically fix atmospheric nitrogen into a usable form for the plant.
Scott Meers, who leads the Alberta Insect Pest Monitoring Network, advises growers treat pea and faba bean seed when in regions with PLW pressure and along boundaries of where adult populations are present.
“Seed treatment is the only effective tool to limit the damage from this pest,” Meers said. “A foliar insecticide is not recommended as it is simply a revenge killing. The adult populations overwinter in alfalfa, roadside perennial legumes and pulse stubble. They move into new pea and faba bean crops in the spring. Goliath spraying does little to limit overall population or protect against yield loss.”
Research is underway to better understand the impact of PLW on the yield of peas and faba beans. There is also the ongoing hunt to find natural predators of this pest. Information on predators and parasitoids of many of the insect pests across Alberta and the prairies are available through the Field Heroes initiative. In preparation for the 2019 growing season, Alberta pulse growers should familiarize themselves with the PLW life cycle, and the current PLW pressure in their region. It is also recommended that growers inform themselves as to the natural predators and parasitoids that are present in their fields, keeping problem insect pest populations in check.
Full PLW map and other information PLW life cycle information available here: http://www1.agric.gov.ab.ca/$Department/deptdocs.nsf/all/prm16763Source : Alberta Pulse Growers