Pest Alert: Flea Beetles are Out!
Join us for our upcoming workshop, Organic Gardening In Missoula: Pests, to learn about the pests and diseases that commonly plague us in the Missoula Valley, and how to safely and effectively treat them! This workshop will take place on Saturday, June 25, 2022 from 10-noon.
Have you seen this in your garden lately?
Or this on your tomato plants??
What about this on your cabbage or broccoli???
You've got flea beetles! One of our earliest garden pests has arrived. Learn more below.
What are they?
Flea beetles are a prevalent pest in vegetable gardens. Adult flea beetles are tiny, ranging in size from 1/16 –1/8th inch long. There are many species of flea beetles; most adults are small, darkly colored, sometimes shiny or metallic, and jumpy when you get close. They are also strong fliers.
Symptoms:
You can often see Flea Beetles and the damage they cause. Adult flea beetles cause the most damage by feeding on foliage, cotyledons, and stems. Young vegetable seedlings are most sensitive to this onslaught. As flea beetles feed, they create shallow pits and small rounded, irregular holes (usually less than 1/8th inch) in the leaves, resulting in a tiny shotgun hole appearance. They primarily affect radishes, mustard greens, broccoli, cabbage, turnips, eggplant, peppers, tomatoes, potatoes, spinach, and melons. While the damage looks devastating, most healthy plants will recover and this seasonal pest will pass.
Know your enemy:
Flea Beetles overwinter in the garden, taking advantage of plant litter, woody materials, and perennial vegetation. In early spring, the adults become active and begin laying eggs in the soil. Following egg hatch, tiny white larvae feed on the roots of the newly planted seedlings, usually causing little to no damage to the plants (except for potato flea beetle larvae and sometimes tomatoes). Adult flea beetles cause the most damage by feeding on the foliage.
A heavy flea beetle attack can result in wilted or stunted plants. Transplants can generally withstand more damage than plants started from seed, although both can be severely injured if flea beetle numbers are high. The good news is that adult flea beetle populations often decline throughout the summer, and most healthy plants can push through a flea beetle infestation. Once crops reach the 4- or 5-leaf stage, the plants are usually well established and can tolerate feeding damage. Give your plants an extra boost to beat the flea beetle by applying liquid fish emulsion fertilizer several times a week (follow all labeled directions).
Treatment options:
Hand squish any beetles that you see and can get your hands on. They are a bit slower in the cool mornings and evenings.
Since these bugs jump and move around a lot, you can often catch them in a sticky trap laid at the base of your infested plants.
Pyrethrin spray is a standard treatment. Use it sparingly, as needed, to kill flea beetles. Although this insecticide is acceptable by USDA organic standards, use it carefully since it can kill beneficial bugs. Spray tops and bottoms of leaves on affected plants. Make sure it is organic, or OMRI certified. No rotenone or synthetic pyrethroids.
Mix biodegradable dish soap with water into a spray bottle: 1 tablespoon of soap in a 1-liter spray bottle. You can also add Neem oil to this mixture. Apply the mix on the tops and bottoms of the leaves of affected plants.
Fertilize and "baby" your plants. Healthy plants will overcome this seasonal pest. Choose healthy transplants, keep your plants well-watered, fertilize with an organic or sustainable fertilizer (see recommendation above), keep the area weed-free, and provide protection from frosts if needed. Generally, keep an eye on your plants as much as possible. Stressed plants attract pests, so work to reduce any other stresses or competition to the plant.
Looking for more information on other garden pests? Check out this other blog: “The Top Four Pests in Missoula and What to Do about Them”.
Updated June 9, 2022, by Emily Kern Swaffar, Updated: June 1, 2021, by DeHanza Kwong, Originally Published Jun 11, 2019, by Emily Kern
Source: University, Utah State. “Flea Beetles on Vegetables.” USU, 27 Apr. 2021, extension.usu.edu/pests/research/flea-beetles-vegetables.