Management of lygus and seedpod weevils in canola at the farm level

The Challenge

It seems that if a grower seeds early they are at a higher risk of seedpod weevils, but later seeded fields may be at greater risk from lygus bugs. Spraying insecticides impact more than pests, therefore reassessing the potential risk with the economic threshold and climatic variables are necessary to increase the economic variability of canola production.

The Project

Develop a management plan that growers can consider when determining how to deal with pressure from both cabbage seedpod weevil and lygus concurrently.

The Results

• Spraying insecticide at the early flower stage for cabbage seedpod weevils reduced the abundance of lygus bugs at the pod stage in most cases
• Overall, spraying at the early flower for weevils resulted in an average yield increase of around 1.5 bushels per acre compared to unsprayed fields;
• Seeding in April increased the risk of weevil damage but reduced that of lygus; the opposite occurred in fields seeded in late May and those seeded in early May had intermediate pest abundances.
• Lygus abundance at early flower was not correlated with subsequent abundance at later crop stages even a week later; this was in contrast to the case of seedpod weevils and related to the more complex life cycle of lygus bugs.
• Researchers recommend using an economic threshold for lygus at one per sweep, and to keep the current 2-3 per sweep for cabbage seedpod weevil, regardless of prices for canola.

Grower Benefits

Ensuring pests have reached their economic threshold before spraying insecticide is essential for yield and economic benefit.