Flea beetles are a common pest in South Dakota vegetable gardens. This spring was relatively warm and dry throughout much of the state, making ideal conditions for flea beetle activity. Recent weather, especially in areas affected by drought, has caused flea beetle populations to increase rapidly and become more of an issue than usual for many gardeners.
Description & Behavior
Flea beetles overwinter as adults and become active by mid-spring. The adults will feed for about a month before they begin laying eggs in the soil. Larvae soon hatch and burrow down to feed on the roots of nearby plants. After another month, the larvae pupate and emerge as adults. This cycle may continue through a second and even a third generation, depending on the species.
Flea beetle adults cause the majority of injury to plants, and exhibit characteristic defoliation known as “shot hole” injury. This occurs when the beetles chew numerous small holes on the leaves of infested plants, making them look as if they have been hit by a shotgun blast (Figure 1).The adults are small (< 1/8 inch), dark colored, and typically have a shiny appearance (Figure 2). Flea beetles get their name because of their enlarged hind legs that are used for jumping. When disturbed, the adult beetles will spring away, much like the behavior of a flea.
There are a few common species of flea beetles, and each prefers a different set of host plants. As the name suggests, the cabbage flea beetle is a pest on cruciferous plants (cabbage family). Flea beetles in the genus Epitrix are especially fond of plants in the nightshade family which includes eggplants, tomatoes, potatoes, and peppers.
Figure 2. Adult flea beetle. Credit: P. Wagner.
The first step towards management is always prevention. Using floating row covers or surrounding susceptible plants with fine mesh screening can help prevent flea beetles from getting in. Keep in mind that row covers can be challenging to use in areas with high winds.
Planting a trap crop nearby can attract flea beetles away from the garden. Radishes and mustard plants both work well as trap crops and can be either sprayed or destroyed once they become infested. Other preventative options include organic products such as neem oil and diatomaceous earth. These products can be put on and around plants to work as natural repellants that keep flea beetles away or deter them from feeding.
Once an outbreak occurs, alternative methods should be used to eliminate flea beetles. Releasing entomopathogenic nematodes acts as a form of biological control. The nematodes help eliminate flea beetle larvae that are developing in the soil, resulting in reduced adult emergence. To manage adults, place yellow sticky cards throughout the garden to trap and kill the flea beetles. Insecticides containing carbaryl, permethrin, spinosad, or bifenthrin are also effective against adult beetles. However, they must be reapplied every 1-2 weeks to provide consistent population management. Always remember to check the product label on insecticides to ensure that they are approved for the crop that you are using them on. Furthermore, it is important to be aware of any special instructions regarding crop harvest following an insecticide application.
- Bunn, B. 2015. Flea Beetles on Vegetables. Utah State University Extension.
- Cranshaw, W. S. 2013. Flea Beetles. Colorado State University Extension.