Young spring canola plants may fall prey to a variety of biotic and abiotic threats. Many biotic threats such as insects may be controlled by thorough scouting and timely management. Flea beetles are one such insect pest. Flea beetles which are only 1/10 of an inch long can cause severe damage to young canola resulting in reductions in yield when massed in large enough numbers. To determine whether you should act against flea beetles, you should understand the nature of the threat posed to crop yield and the thresholds at which actions are required.
Flea beetles overwinter as adults in leaf litter and emerge to feed on brassica’s when the temperatures warm. The flea beetles lay their eggs in the late spring and the next generation of adults emerge in the late summer. The presence of adults in both the spring and the fall means that flea beetles can be a pest in both spring and winter canola. Flea beetles primarily feed on the cotyledons of canola seedlings and can cause seedling death if populations are high enough. Generally, flea beetle damage is most intense on the edge of the field and decrease as you progress inwards. A variety of risk factors can contribute to economically important flea beetle damage.
Risk Factors
Flea beetle damage becomes a concern in dry, warm years, with poor stand establishment. With the unusual dryness this spring and rising temperatures, it is prudent to scout canola fields to assess for flea beetle damage.
Controlling Flea Beetles
Because flea beetles can travel great distances crop rotation and other cultural practices provide a limited utility in controlling flea beetles. In most instances, a neonicotinoid seed treatment will keep flea beetles below economic thresholds. However, if a canola stand is sparse and/or slow-growing it may require a foliar insecticide. To determine if a foliar insecticide is required you should scout the field to see if flea beetle pressure has exceeded the action threshold. The action threshold for flea beetles is when leaf damage has reached 25% (Figure). Both North Dakota State University and the Canola Council of Canada have published extensive resources on flea beetles. Please follow the links below to learn more about flea beetle damage and control in spring canola.
The action threshold for foliar insecticide application is 25% foliar damage. Photo credit: Bayer Crop Science.
Resources
- Integrated Pest Management of Flea Beetles in Canola: Life Cycle (Figure 6)
- Canola Council Flea Beetles
For questions or comments, contact Dale Whaley via email at dwhaley@wsu.edu or phone at 509-745-8531.