Flea beetles are common and problematic in gardens and fields across the United States and much of the world. These small, jumping beetles feed on leaves, creating irregular holes that look like the plants have been riddled with BB or shotgun shots. The best way to manage flea beetle populations is by using cultural prevention methods, biological controls, and chemical insecticides.
Flea Beetle Basics
Flea beetles aren’t related to fleas, but this class of leaf beetles has enlarged back legs that make them jump like fleas when disturbed. They are small leaf beetles in the Chrysomelidae family, ranging in size from one-sixteenth to one-eighth of an inch, and shades of black, bronze, brown, blue, and gray, depending on the species.
They are an incredibly frustrating pest to deal with and impact crops and gardens worldwide, causing significant economic problems. Flea beetles are less problematic in ornamentals, trees, and shrubs but cause occasional damage.
How Many Species of Flea Beetles Exist?
Flea beetles make up the largest subfamily (Alticinae) within the Chrysomelidae or leaf beetle family, one of the most destructive insect families. The flea beetle subfamily contains approximately 6,000 plant-feeding species worldwide, with most species feeding on one type of plant (monophagous) or a few related plants (oligophagous). Very few are generalist feeders that attack a wide range of hosts.
Where Can You Find Flea Beetles?
You can find flea beetles worldwide, and it’s not unusual for any given area to have many species. In the US, it isn’t uncommon for a state to have upwards of thirty different species. Populations are usually based on locally-grown plants, but the range of specific types has increased in the last few decades.
Common Flea Beetles and the Plants Affected
Different flea beetle species feed on different garden plants and field crops. Commonly attacked vegetables include beans, broccoli, cabbage, cauliflower, eggplant, peppers, potatoes, radishes, spinach, tomatoes, and turnips. They also infest field corn, sweet corn, canola, soybeans, sorghum, and small grains.
The host plants are typically related to the beetle’s common name. Most flea beetle types prefer one plant or a few closely related plants.
- Blueberry flea beetle (Altica sylvia ‘Malloch’)
- Cabbage stem flea beetle (Psylliodes chrysocephala)
- Corn flea beetle (Chaetocnema pulicaria)
- Crucifer flea beetle (Phyllotreta cruciferae)
- Eggplant flea beetle (Epitrix fuscula)
- Grape flea beetle (Altica chalybea)
- Hop flea beetle (Psylliodes punctulata ‘Melsh’)
- Horseradish flea beetle (Phyllotreta armoraciae)
- Mint flea beetle (Longitarsus waterhousei)
- Pale striped flea beetle (Systena blanda)
- Potato flea beetle (Epitrix cucumeris)
- Red-headed flea beetle (Systena frontalis)
- Spinach flea beetle (Disonycha xanthomelas)
- Striped flea beetle (Phyllotreta striolata)
- Sweetpotato flea beetle (Chaetocnema confinis)
- Western black flea beetle (Phyllotreta pusilla)
Life Cycle of Flea Beetles
The flea beetle goes through a standard four-stage life cycle of complete metamorphosis like other insects: egg, larvae, pupa, and adult. Each stage has a different appearance than the one before and the one after. Depending on the species and the climate, you may see one to three generations per year.
- Adult flea beetles overwinter underground and beneath leaf litter or other plant debris. They emerge in early spring once it warms to 50°F and begin feeding for several weeks. After mating, they lay eggs in the soil near the base of the host plants.
- It takes seven to fourteen days for eggs to hatch. Newly hatched larvae feed on underground stems and roots until they are fully grown.
- They pupate beneath the soil surface in earthen cells for eleven to thirteen days and emerge as adults.
- After emerging, the adults begin voraciously feeding on nearby plants. They are particularly active on calm, warm, sunny days.
Identifying Flea Beetle Larva and Adults
- Flea beetle larvae are tiny—one-eighth to one-third of an inch long—creamy-colored worms. They are found underground, feeding on germinating seeds and the roots or tubers of young plants.
- Adult flea beetles are typically shiny black, bronze, dark brown, blue, or gray and about one-tenth an inch long. Some species have yellow on white stripes on their wing cases. They have large, powerful hind legs that give them their jumping ability.
What Does Flea Beetle Damage Look Like?
Flea beetle damage is easy to spot, and the unique pattern is often called “shotholes,” as they look like BB-sized holes in the leaves. Adults feed on the stems and leaves, creating shallow pits and gaps that are roughly circular, and span no more than one-eighth of an inch. Heavy feeding results in defoliation.
Damage is usually the worst during spring and early summer, tapering off as the season progresses.
Are certain plants more susceptible to flea beetle damage?
Seedlings and young plants are more susceptible to flea beetle damage than older, mature plants. The growth of young plants can be significantly stunted, and in the case of severe infestations, flea beetle damage can kill plants. They are more vulnerable to injury because they have less leaf surface area than larger plants.
How much damage can plants sustain?
Feeding damage often looks very severe, but it might not be critical to plant health if the plants are well-established. Yield decreases begin when 25% of the leaf area has been eaten. A crop is considered an economic loss when there is a 50% leaf area loss—at this point, the profit of the actual yield is less than the cost of control.
Managing Flea Beetles Using IPM
The most effective way to manage flea beetles is using an integrated pest management (IPM) approach. IPM is an ecosystem-based approach that uses prevention practices and biological control to control numbers. Pesticides are used when populations become uncontrollable but done in a way that minimizes environmental risks, beneficial insects, and human health.
Flea beetles are not difficult to control in most cases, but the damage isn’t typically realized until plants are seriously injured. Because of this, it is essential to regularly scout susceptible plants, especially tender seedlings.
Cultural Practices to Prevent Flea Beetle Problems
- Clean up fallen leaves and plant debris in the fall so the beetles have minimal habitat for overwintering.
- Plant a trap crop—a highly-favored plant—before planting your garden. Adult flea beetles are attracted to the earliest, tallest plants available. At this point, you can also spray the trap crop once flea beetles are actively feeding.
- Choose resistant plant varieties if they are available for purchase.
- Use companion plants to repel or confuse flea beetles, keeping them away from host plants. Marigolds, dill, and green onions are excellent choices.
- Time planting around insect emergence and spring feeding activity. Flea beetles emerge after the leaf litter thaws in spring, usually in late April or early May, when there is extended warm weather.
- Plant as early as possible to maximize plant size before beetle emergence.
- Wait to get plants in the ground as late as possible. Waiting until it’s warmer directs beetles to other plants, and the warm weather helps plants grow quicker, so they can better resist damage.
- When seedlings are germinating, cover your plants with row covers or insect netting to protect them from beetles. Before the plants flower, remove the covers to allow pollinators to reach them.
Using Biological Methods to Control Flea Beetles
Biological controls are critical to managing flea beetle populations, especially beneficial insects and other predators. They can help reduce numbers before they become problematic and reduce the need for chemical pesticides. Unfortunately, because the beetles emerge in such high numbers during a short period, the effect of biological controls is limited.
- Insect predators include lacewings, field crickets, adult big-eyed bugs, damsel bugs, and a braconid wasp (Microctonus vittatae) native to the eastern United States.
- Some entomopathogenic nematodes attack and feed on the flea beetle larvae, helping to reduce adult populations.
- The fungus Beauvaria bassiana causes white muscadine in flea beetles, a disease that kills insects within a few days of contact. You can purchase the pathogen from retailers and water it into the soil.
Are Chemical Control Options Effective?
When an infestation is out of control, chemical insecticides are an effective treatment method, and there are many labeled for use on flea beetles. When using insecticides, ensure your garden vegetables or ornamentals are listed on the pesticide’s label—which signifies you can treat them with the selected pesticide—and follow the label directions.
Flea beetles are susceptible to numerous active ingredients commonly found in garden pesticides, making it easy to find a suitable product at a local retailer.
- Pyrethrins or pyrethrum
- Lambda cyhalothrin