What to do now about flea beetles

Marissa Schuh, Horticulture IPM Extension Educator. Originally published in 2023, updated in 6/8/2024.

Flea beetle continues to be one of the biggest pests on Minnesota vegetables farms, especially in our brassica crops. Some of the most effective things we can do to manage this pest happen before we see damage (AKA, the combination of rotation and row covers).  We're past the window where that particular tact can be taken, as applying row covers where flea beetles are already feeding just keeps them close to our crops.

Flea beetle damage on mustards. Whitney Cranshaw, Colorado State University, Bugwood.org

Quick refresher on some key things that can be done about flea beetle at this point in the growing season.

• The larger the crops are, the more resistant they are to feeding (though they do often feed on what we are hoping to sell). Solanaceous crops may be getting to the point where flea beetle feeding matters less.
• Kaolin clay can provide a physical barrier to feeding (but doesn’t always work, and isn’t a good fit for leafy brassica greens)
• Some growers feel beneficial nematode introductions have been helpful in bringing populations on their farms down. University research trials on flea beetles and nematodes have been mixed.

This is often a pest that is managed with pesticides. Things to consider if going this route...

• If 10-20% of the leaf area of plants are damaged, consider spraying.
• Flea beetle damage may be concentrated at the edges of the field or in hot spots in the field. Spot treatments can sometimes be effective while saving time and money.
• For conventional pesticide options, see the Midwest Vegetable Production Guide.
• On the organic side, product performance is mixed. Pyrethrin and spinosad products have performed the best, but even then, they often don’t give great control. 

This pest is rarely a one-off occurrence, so make a note in your calendar to make a plan for integrating more cultural controls into next year's growing plan.

The lifecycle of the crucifer flea beetle. Illustrations by Martha Sudderth. Created with BioRender.com by Marissa Schuh.