Do not let flea beetles go undetected in your garden. Ignoring these insects for too long can result in extensive damage, including stunted plant growth, blighted leaves, and wilting. Not only do they eat holes in plants, but they can also spread plant diseases. Young plants may even die if attacked.
You will save yourself a lot of time, effort, and money by learning what the symptoms of an infestation are beforehand so that you can be on the lookout for these garden pests.
Profile of the Flea Beetle
The flea beetle is a type of jumping beetle; it is its large, powerful hind legs that allow it to leap, which is what it typically does when disturbed. In fact, it gets its common name from the fact that its jumping behavior reminds people of the way fleas (Siphonaptera) jump around. There are many genera; examples include:
The different genera do not all look alike. Most flea beetles, however, have the following traits:
- They are about 1/16 inch long.
- They are often black. But, less commonly, they can be tan or other colors (including mixed colors).
- Their shell is shiny.
The different types of flea beetles are sometimes named for the specific plants that they target. For example, the potato flea beetle (Epitrixcucumeris) eats potato plants, while the spinach flea beetle (Disonycha xanthomelas) eats spinach.
Flea Beetle Life Cycle
Flea beetles have a life cycle that involves a larval stage and an adult stage. They do damage to plants in both stages, but the damage done in each stage is different. The life cycle (which varies somewhat according to the species) is as follows:
- In late fall, the adults burrow down into your garden's soil, leaf litter, or garden debris to overwinter (some types may go into wooded areas).
- They become active in spring and start eating the leaves of your plants when outdoor temperatures climb consistently to about 50ºF. This is when the worst damage is done, especially considering that this is also when young plants (which are affected the worst) are emerging.
- In summer these adults lay the eggs that will result in the next generation of flea beetles. These eggs are laid at the base of a plant's stems.
- When the eggs hatch, the larvae that come out eat the roots of your plants for 2 or 3 weeks.
- After undergoing a short (about 1 week) pupal stage, they emerge as adults. They then start to eat the leaves of plants. It's this second generation that does the most damage to fall crops before overwintering.
Plants Commonly Damaged by the Flea Beetle
Flea beetles feed on a variety of plants, including weeds such as pigweed (Amaranthus spp.). Vegetable plants are especially prone to damage from flea beetles; examples include:
- Broccoli (Brassica oleracea var. italica)
- Cabbage (Brassica oleracea)
- Eggplant (Solanum melongena)
- Watermelons (Citrillus lunatus)
- Peppers (Capsicum annuum)
- Radishes (Raphanus sativus)
- Tomatoes (Solanum lycopersicum)
- Turnips (Brassica rapa)
But some ornamental plants are also eaten by flea beetles, including:
- Dogwood (Cornus spp.)
- Crepe myrtle (Lagerstroemia spp.)
Symptoms of a Flea Beetle Infestation
Because the different types of flea beetles do not all look alike, it is easier to detect an infestation based on what the damage that they cause looks like.
Flea beetles chew irregular holes in the foliage of plants. Some of the holes go all the way through the leaf; others do not, merely leaving a blemish. The resulting damage is sometimes called a "shothole wound" because it looks like the result of a miniature shotgun having been fired at the affected leaf.
Steps to Take for Flea Beetle Control
The best way to control flea beetles is not to let them gain a foothold in your garden in the first place. Preventive steps that you can take include:
- Growing certain strong-smelling plants in the garden that tend to repel flea beetles. One example is catnip (Nepeta cataria)
- Placing row covers over your garden crops
- Keeping your garden free of weeds in early spring so that emerging flea beetles have less to feed upon
- Delaying the planting of crops in spring if possible. This deprives flea beetles of needed early sustenance. Plants also grow more vigorously in warmer weather and are better able to withstand flea beetle feeding
- Tilling your garden in late fall, which disturbs those flea beetles attempting to overwinter in your soil.
- Making sure that you pick up any garden debris that flea beetles might want to overwinter in when you put your garden to bed for the winter.
If you have not been fortunate enough to have enjoyed success at preventing flea beetles and find yourself with an infestation, you can address it through either application of pesticides or by other methods:
- Apply Neem oil, which is organic.
- Apply any of the other commonly sold pesticides that are labeled as being effective against flea beetles. For example, pyrethrum-based and spinosad-based pesticides are widely available at home-improvement stores.
- Attract beneficial insects to the garden (or buy them). Examples that eat the larvae of flea beetles are braconid wasps (Microctonus vittatae) and tachinid flies (Tachinidae family).
- If you are confident that you can identify a flea beetle by looking at it, then sticky traps are also effective. Check your sticky traps regularly and inspect them for flea beetles. If you find any, take control measures immediately. Spring is the best time to set out sticky traps.