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Quick facts about flea beetles
- Flea beetles are common pests found on many vegetable crops including radishes, broccoli, cabbage, turnips, eggplant, peppers, tomatoes, potatoes, spinach and melons.
- Flea beetles chew irregular holes in the leaves.
- Severe flea beetle damage can result in wilted or stunted plants.
- Flea beetles are best managed through a combination of nonchemical and pesticide methods.
How to identify flea beetles
Flea beetles are a type of leaf beetle in the family Chrysomelidae.
Most adult flea beetles are very small (1/16 –1/8th inch long). An exception is the spinach flea beetle, which is 1/4-inch long.
- Flea beetles can be black, bronze, bluish or brown to metallic gray.
- Some species have stripes.
- All flea beetles have large back legs which they use for jumping, especially when disturbed.
The most common flea beetles in Minnesota gardens are:
- crucifer flea beetle (Phyllotreta cruciferae)
- striped flea beetle (P. striolata)
- western black flea beetle (P. pusilla)
- potato flea beetle (Epitrixcucumeris)
- spinach flea beetle (Disonycha xanthomelas)
Most flea beetles feed on very specific plants, but the palestriped flea beetle (Systena blanda) feeds on a variety of plants, like, squash, beans, corn, sunflowers, lettuce, potatoes and many weeds.
Life cycle of flea beetles
Flea beetles live through the winter as adults in leaf litter, hedgerows, windbreaks and wooded areas.
Adult flea beetles become active in early spring. Depending on the species, females lay single or clusters of eggs in small holes, in roots, soil or leaves of many vegetables as well as occasionally on flowers and ornamental shrubs and trees.
Small white larvae hatch from eggs and feed on the roots of the newly planted seedlings.
Larvae then transform into pupae in the ground. There are usually one to two generations per year.
Damage caused by flea beetles
All types of flea beetles cause similar damage.
Adult flea beetles cause the most damage by feeding on the leaves and stems. They create shallow pits and small rounded, irregular holes (usually less than 1/8th inch) in the leaves. This type of damage is unique to flea beetles.
Plants started from seeds are less tolerant of feeding damage compared to transplants, but both can be severely injured if flea beetle numbers are high.
The larvae usually cause little to no damage to the plants (with the exception of potato flea beetle larvae).
How to protect your plants from flea beetles
Flea beetles are most damaging in spring. It is important to monitor for their activity as soon as seedlings have emerged.
- Place yellow sticky traps in your garden to see if you have flea beetles.
- Check your plants for flea beetles and their damage.
- Prevent severe damage to your plants by treating seedlings when there are more than five flea beetles per plant.
- Protect your crops if 10-30% leaves on seedlings and transplants have dropped off.
It is generally not necessary to treat flea beetles during summer, especially at the end of the season. By summer, crops reach the 4- or 5-leaf stage and are strong enough to survive feeding damage. The number of adult flea beetles also goes down at that time.
Cole crops (cabbage, broccoli and cauliflower) and other plants with edible greens can be damaged later in the summer. Monitor and treat them as needed.
Make gardens unwelcoming to pests
Control weeds in and around planting sites to limit food sources for flea beetles.
- Remove old crop debris so that beetles will not be able to get protection in the winter.
- Plant crops as late as possible. Plants grow faster in warmer temperatures and are more stable to resist damage from flea beetles.
Keep flea beetles out of the vegetable crop
- Use row covers or other screening to keep beetles out, when the seedlings are growing.
- Remove row covers before the flowers come up so pollinating insects can reach the plants.
- Plant a highly-favored crop, such as radish, as a trap crop, before you plant your main crop.
- Adult flea beetles will be attracted to the tallest, earliest crops available.
- Once beetles are actively feeding on the trap crop, spray with a labeled pesticide.
Natural enemies can control flea beetles
Microctonus vittatae is a native braconid wasp (found more commonly in the eastern half of the U.S). This wasp kills the adult flea beetle. The larvae of this wasp develop on the female flea beetle and prevent the beetle from reproducing.
There are many pesticides labeled for treating flea beetles. Below are names of active ingredients that are commonly available in pesticides sold in stores that sell garden pesticides:
- lambda cyhalothrin
CAUTION: Mention of a pesticide or use of a pesticide label is for educational purposes only. Always follow the pesticide label directions attached to the pesticide container you are using. Remember, the label is the law.
Be sure that the vegetable you wish to treat is listed on the label of the pesticide you intend to use. Also be sure to observe the number of days between pesticide application and when you can harvest your crop.
Reviewed in 2018