Flea beetles
Order: Coleoptera
Family: Chrysomelidae
Description
Flea beetles are small insects that can jump when threatened. They are beetles, have sclerotized pair of hind wings and chewing mouthparts. Adults range in length from 1.75-4.3 mm (1/15–1/6 inch) and have enlarged hind legs for jumping. They can be brown, green, or metallic-blue to black, depending on the species. Some species also have stripes or spots on the hind wings. The eggs are white to yellowish-gray and very small at 0.4 mm (1/64 inch) long. The appearance of larvae depends on the life history of the species; larvae that feed on roots are small, pale, and worm-like with a brown head capsule, while those that feed on foliage are black or gray and have small legs.
Feeding injuries inflicted by flea beetles can kill plants or significantly retard their growth and are particularly destructive in seedlings and young leafy vegetables. While flea beetles can be found on a variety of plants, they tend to prefer feeding on a few closely related species. They feed on plants in the nightshade family such as tomatoes and potatoes, and crucifer crops such as broccoli and cabbage.
There are dozens of species of flea beetle in Colorado. Those that attack vegetables include the western black flea beetle (Phyllotreta pusilla), palestriped flea beetle (Systena blanda), potato flea beetle (Epitrix cucumeris), tobacco flea beetle (Epitrix hritipennis), tuber flea beetle (Epitrix tuberis), horseradish flea beetle (Phyllotreta armoraciae), and spinach flea beetle (Disonycha xanthomelas). The western black flea beetle feeds on various cruciferous plants. The palestriped flea beetle has a very wide host range that includes squash, beans, corn, sunflowers, lettuce, and potatoes. Potato flea beetles feed on plants in the nightshade family, especially tomatoes and potatoes. The tobacco flea beetle feeds on eggplant and other plants in the nightshade family. Larvae of the tuber flea beetle feed on potato tubers. The horseradish flea beetle attacks horseradish and other mustards. Spinach flea beetles attack beets, spinach, and other related plants.
Quick Facts
- Flea beetles include various beetle species that can jump away from disturbances.
- Of the dozens of flea beetle species inhabiting Colorado, several are considered pests of vegetables. Collectively, they attack plants in the nightshade family, cruciferous plants, and leafy greens.
- The larvae of some species dwell in soil and feed on plant roots, while the larvae of other species feed on leaves.
- Feeding injuries on young plants or seedlings can result in stunted growth or death of the plant. Plants that are well cared for can often outgrow feeding injuries due to flea beetles.
Palestriped flea beetle. Image credit: Whitney Cranshaw, Colorado State University, Bugwood.org
Potato flea beetles on potato. Image credit: Whitney Cranshaw, Colorado State University, Bugwood.org
Tobacco flea beetle on tobacco leaf. Image credit: Clemson University – USDA Cooperative Extension Slide Series , Bugwood.org
Tuber flea beetle. Image credit: Agriculture Canada, Ottawa , Bugwood.org
Horseradish flea beetle on horseradish leaf. Image credit: Mariusz Sobieski, Bugwood.org
Spinach flea beetle. Image credit: Kansas Department of Agriculture , Bugwood.org
Larvae of the tuber flea beetle. Image credit: Agriculture Canada, Ottawa, Bugwood.org
Western black flea beetle and the feeding injury it causes. Image credit: Whitney Cranshaw, Colorado State University, Bugwood.org
Life history and habits
Flea beetles overwinter as adults in sheltered sites such as under leaves, clods of dirt, or on weeds along the field margins. Activity resumes on warm days in spring as the overwintered beetles begin seeking out host plants for feeding. These beetles are strong flyers and can disperse long distances while searching for host plants. Adults feed on foliage, while larvae feed on foliage or roots, depending on the species. Eggs are laid on leaves or in soil, depending on feeding behaviors of larvae. Species with larvae that develop in the soil, such as the potato flea beetle, typically produce two or three generations each growing season. Species with larvae that feed on foliage tend to produce a single generation each year. Mature flea beetle larvae pupate in the soil.
Injury
Young plants and seedlings are the most susceptible to feeding injury of flea beetles. Feeding injuries are often insignificant in established plants. Adult beetles feed on leaves and chew small holes in the plant tissue, causing shothole damage in plants with thinner leaves. Feeding injury from adults appear as pits on plants with thicker, waxy leaves. The larvae of some species also feed on leaves and produce large and irregular holes. This feeding injury can retard growth or kill young plants and can also reduce the marketability of certain leafy vegetables. The soil-dwelling larvae of some species can cause scarring on potato tubers, and can also burrow into tubers, leaving tunnels filled with frass (excrement).
Biological control
There are various tactics for reducing injuries to seedlings. Planting seeds or transplants in seedbeds can hasten growth and allow them to compensate for injury. When vegetable crops are well established, most can tolerate significant feeding injury. High seeding rates in home gardens can also lower the concentration of feeding injuries on a particular plant. Highly favored crops can be planted as trap crops to draw beetles away from the main crop. After the main crop is sufficiently established, the trap crop can be harvested or destroyed.
Plantings scheduled during periods of low beetle activity can help prevent feeding injury. Floating row covers or screening can provide a barrier to physically exclude flea beetles while seedlings are becoming established. Thick mulches can limit feeding of soil-dwelling larvae. Sweep nets and portable vacuums can be used to remove beetles from plants but should be done with care since flea beetles will jump from plants to escape disturbances.
Cultural control
Insecticides can be applied when high numbers of flea beetles are present on plants. Some insecticides act as a deterrent to feeding, while others are toxic and kill flea beetles. There is high variation among insecticides with regards to their residual activity. For this pest, it is recommended to apply insecticides that persist longer since the adults are mobile and capable of reinvasion. To protect seedlings, more than one application is likely required since growth emerging after the application will be susceptible to feeding injury.
Chemical control
Insecticides can be applied when high numbers of flea beetles are present on plants. Some insecticides act as a deterrent to feeding, while others are toxic and kill flea beetles. There is high variation among insecticides with regards to their residual activity. For this pest, it is recommended to apply insecticides that persist longer since the adults are mobile and capable of reinvasion. To protect seedlings, more than one application is likely required since growth emerging after the application will be susceptible to feeding injury.
References
Bunn, B., D. Alston, and M. Murray. 2015. Flea Beetles on Vegetables. Available https://extension.usu.edu/pests/research/flea-beetles-vegetables
CSU Extension Fact Sheet
Download or view the CSU Extension’s PDF fact sheet for your reference.