As many people find themselves finishing up the seeding season, we also find ourselves at the beginning stages of the bug season. If you have been out and about in your fields you have probably noticed small black bugs that are the size of a pin head bouncing around.
The striped and crucifer flea beetles are the two common species that feed on canola in the Canadian prairies. Hop flea beetles can also be found, but occur in low numbers throughout the prairies. All three species can vary in the way they look, how they feed, and when they emerge.
When To Look For Them
Flea beetles emerge in early Spring, and can cause damage to your canola crop from emergence, up until the 3-4 leaf stage. They aren’t picky eaters, and are known to feed on the cotyledons, leaves, stems, roots or any fleshy tissue on the plant. Sunny, warm and dry weather is preferred by the beetles, but less ideal conditions don’t seem to slow them down either. They are known to increase below ground and underside of leaf feeding during the less than ideal conditions.
How To Manage Them
It is important to assess where the bugs are feeding and how much of it there is. Action threshold levels are when average leaf area loss is more than 25%, and it is considered economically beneficial to spray insecticide when the leaf area loss is above 50%. There are no established threshold levels for stem feeding, which is why it is so important to assess where the feeding is taking place. If the flea beetles are actively feeding on leaf tissue, stem tissue and/or the growing point, the action level might be lower.
There are different control options and management practices to help mitigate the damage these guys can have on your canola crop. Seed treatment options like Prosper Evergol and Helix Vibrance are standard on your canola seed to protect against flea beetles, but you can enhance your protection by adding Lumiderm on your seed when you order it. There are also in-crop insecticide control options to cover you off if populations rise and leaf damage is above threshold levels. Lastly, there are cultural control methods such as seeding early to get crop establishment before the emergence of the flea beetles, allowing a higher tolerance to injury. The second practice is increasing your seeding rate, this can help you reduce the impact of the flea beetle damage by spreading it out over more plants allowing for easier recovery from the stress event.
Don’t Fear Though
The sight of these pesky little bugs probably have you wondering a few different things. Such as, why your seed treatment isn’t working. The truth is, it is working. But, with the newer chemistries, the flea beetles have to feed on the plant to ingest the insecticide for it to work. Whereas older seed treatments were used as more of a deterrent or repellent. Also, seed treatments only give a 28-35 day protection window after the crop is seeded, in cooler, dry weather the crop could be slower growing and not past the 3-4 leaf stage so it is at risk for flea beetle damage.
Niki Beingessner CCA, PAg
Sales Agronomist – Yorkton