Flea Beetle Forecast and Control - Frequently Asked Questions

Fall populations are generally indicative of what the following spring populations are going to be like. If high populations are seen at harvest time and on fall weeds it is necessary to prepare for high populations in the spring.

When Do I Start Scouting and What Am I Looking For?

Over wintering flea beetles emerge as early as the end of April from fields and surrounding field areas that are sheltered by trees or debris. Although there are eight flea beetle species that attack canola and mustard only two species, the crucifer and striped, cause significant damage in Alberta. The crucifer beetles are seen in much higher numbers across the province, and are completely black. The striped flea beetle has two amber colored stripes on their elytra and are seen most commonly in northern agricultural regions. Flea beetles prefer plants from the crucifer family. Scouting for flea beetles should be done prior to seeding and after crop emergence. When scouting prior to seeding, producers should look for feeding damage on susceptible plants such as volunteer canola, stinkweed, wild mustard, and lamb's quarters. After crop emergence, monitoring should be done quite frequently, especially in high-risk areas. Damage symptoms include feeding on cotyledons, first true leaves, petioles and stems. What is typically seen is "shot-hole" damage on the cotyledons. Significant damage can occur within a 24-72 hour period, so control measures should be taken at the 25% defoliation threshold. The first 14 days after emergence of the crop is the most critical, since the plant is most susceptible to damage.

What Kind of Control Measures are Available?

Biological control
Predators, parasites and diseases can contribute to lowering populations, but is limited because the establishment of them is not very successful and research is minimal on their affect on flea beetle populations. Flea beetles emerge in large numbers over a short period of time and can overwhelm the predators and parasites.

Cultural control
**When flea beetle populations are high cultural control alone is not enough and chemical control will need to be considered.

• Seed shallow and use high quality, large, vigorous seed- the quicker a seedling can establish itself the more damage it can withstand from flea beetles.
• Seed early - a plant that establishes quickly can ward off flea beetles more effectively. **Caution advised if high populations are seen early in fields when planting. Crops must be monitored daily upon emergence for damage.
• Resistant varieties - none available.
• Crop rotation - flea beetles over winter along field edges and migrate so following a crop rotation does not make your crop immune to flea beetles, but if problems with flea beetles persisted the year before, planting canola again will contribute to high populations once again.
• Direct seeding - provides a microclimate that warms slower than a conventionally seeded crop. Cooler temperatures slow flea beetle activity, reducing damage.
• Trap cropping - not effective when faced with high populations, but can be effective under low to medium populations.
• Increase seeding rates - Increased plant populations means less damage to each specific plant.
• Wider row spacing - reduces the attractiveness to the flea beetles.

• Control cruciferous weeds and volunteer canola early spring - eliminate food for early spring populations.
• Seed treatments - Applied to seed prior to planting. Products are effective, even though there has been some concern regarding the new neonicotinoid insecticides. When populations are expected to be low to medium, a minimum low rate treatment should be considered. But if populations are expected to be high, a high rate treatment should be considered. These insecticides, in combination with a fungicide are absorbed through the seed coat (systemic action) and when feeding on the cotyledon occurs, the flea beetles are killed. Maximum concentrations from seed treatments are reached within a few days of emerging and begin to decline soon after. Please refer to the Alberta Crop Protection book for seed treatment options.
• Foliar insecticides - Foliar sprays are used to control flea beetle populations after crop emergence. When population numbers are high it may be necessary to use a foliar insecticide in addition to a seed treatment. The speed at which high flea beetle populations can destroy crops, makes foliar sprays a necessary tool. Please refer to the current Crop Protection book for foliar insecticide product options.