By Erin Marissa Russell and Matt Gibson
Flea beetles are a common garden pest known to attack a wide variety of garden plants, including ornamentals, fruits and vegetables, feeding on the plant’s foliage by chewing irregularly-shaped holes in their leaves. Severe flea beetle infestations can cause wilting and stunted growth in affected plants. There are multiple flea beetle species that attack garden plants, some of which target certain plant families exclusively, and others feed just about any plant they come across.
Flea beetles seem to be diehard fans of the eggplant, which they feed on voraciously, destroying entire harvests and leaving plants stripped bare. Other commonly targeted crops include beans, beets, corn, spinach, peppers, melons, tomatoes, potatoes, turnips, radishes, and members of the cabbage family like broccoli, kale, collard greens, cauliflower, cabbage, Brussels sprouts, and kohlrabi. The seedlings, young transplants, and early spring growth are especially prone to flea beetle damage. Aside from feeding on garden plants, flea beetles can also spread common garden diseases, like bacterial wilt, to their host plant.
Once identified, flea beetle control is most successfully managed by using a combination of organic and inorganic treatment options. Read on to learn more about how to identify, diagnose, and treat flea beetle damage in your home garden, from small, isolated attacks, to major infestations.
Identifying Flea Beetles
There are many different species of flea beetles, which can make identifying flea beetle attacks somewhat difficult, as flea beetle species come in a wide variety of sizes and colors. The small, skinny, worm-like larvae grow to between one-eighth and one-third inch long. Adults measure between one-sixteenth and one-fourth inch long, depending on the species.
The majority of the adult flea beetles that target vegetable plants are shiny and either black or dark brown. Aside from black and brown, flea beetles also come in various shades of blue, green, and bronze, and can also be striped or metallic. Flea beetles are named after the common flea because, like the flea, they jump when they are disturbed.
Flea Beetle Species
Corn Flea Beetle – This flea beetle species is known to feed on all species of corn, especially plants under six inches tall. However, the corn beetle is feared less for the damage that it causes to young corn plants, and more for the company it keeps. The corn flea beetle is also a known carrier of the microorganism that causes Stewart’s Wilt, a very serious bacterial plant disease that can severely damage corn crops. The tiny, black, pinhead-sized beetles can be a nightmare for corn croppers.
Grape Flea Beetle – The grape flea beetle causes quite a bit of damage to new growth and the immature buds on grape vines during the spring and summer. The larvae feed on the plant during the spring, and the dark metallic blue adults return to the vines to eat their heart out for the entire summer. At nearly a half inch in size, the adult grape flea beetle can do quite a bit of damage.
Mint Flea Beetle – The larvae of the mint flea beetle cause more damage to the plant by chewing on the root system than the adult beetles do to the leaves, though in hot areas, adult leaf damage can cause leaf fall. The very small, one-twelfth-inch adults are yellow-brown and pale with deep brown heads and black eyes.
Palestriped Flea Beetle – The palestriped flea beetle has a voracious appetite and a wide-ranging palate. It dines on corn, beans, cabbage, peas, strawberries, and tomatoes, among other crops. It even has a taste for a few allergen-causing weeds, including ragweed. Adults are one-eighth inch long, and can vary in color from metallic red to yellow-brown. It gets its name from the pale yellow stripe that runs along the beetle’s wings.
Potato Flea Beetle – The potato flea beetle doesn’t just damage potato plants. Despite their name, they bully just about every plant in your vegetable garden, including potatoes, eggplant, tomatoes, green peppers, and other nightshade plants, as well as sunflower, morning glory, and some common weeds. Though the tiny, black, one-sixteenth-inch potato beetle is small in stature, it packs a serious punch. One of the most widespread pests, the potato beetle is a ferocious crop killer.
Red-Headed Flea Beetle – A common pest to cabbage, bean, beet, and potato plants, plus a few garden weeds, the red-headed flea beetle has a diverse palate and is large enough to cause these plants considerable injury. The one-sixth-inch long beetles have reddish-orange heads and black bodies.
Spinach Flea Beetle – At nearly one-fourth inch long, the spinach flea beetle is the largest known flea beetle species. Sporting a yellow-orange thorax paired with dark, green-black wings and helmet, the spinach beetle is one of the only beetles to lay its eggs on the leaves instead of the base of the plant. You can find the larvae on the underside of the leaves, while the adults feed from the top. Spinach flea beetles hatch two generations per year. The first round typically feeds on weeds, and the second generation, which has a more refined palate, feasts on beets and spinach plants.
Striped Flea Beetle – The adult striped flea beetle gets its name from the wavy yellow stripe that adorns each of its wings. It’s one-twelfth-inch body is otherwise black. This flea beetle species has a taste for cruciferous vegetables, attacking cabbage, mustard, turnip, radish, and broccoli crops, and its larvae can seriously damage root veggies like turnips and radishes.
Sweet Potato Flea Beetle – The tiny, one-sixteenth-inch sweet potato beetle feeds on morning glory, sweet potato, and bindweed. It can be quite destructive to the foliage of sweet potato crops, which can slow the growth of their tubers in severe cases. Their damage differs from other flea beetles, as holes appear more like tiny slices, or cuts in the leaf surface.
Life Cycle of Flea Beetles
Adult flea beetles survive the winter by burrowing into the soil or by hiding out, either in plant debris like leaf litter, or in windbreaks, wooded areas, and hedgerows. After spending the winter avoiding the cold, adult flea beetles emerge in early spring with a voracious appetite and a natural need to propagate their species. Depending on the particular species, female flea beetles will lay individual eggs or egg clusters in tiny holes in the roots, in the soil surrounding the target plant, or on the leaves of a wide variety of vegetable plants. Though vegetable plants are the most common victim of flea beetle infestations, flowers, as well as ornamental shrubs and trees, are also susceptible to attacks.
Small, white, thin, worm-like larvae hatch from their eggs and begin feeding on the roots of seedlings, as well as on younger, smaller plants in the garden. Then, the larvae transform into pupae while hiding beneath the soil, where they will soon become adults, biding their time until temperatures rise in the spring. As winter fades into spring, adult flea beetles climb out of the soil once more. Depending on the species, there can be one to two flea beetle generations each calendar year.
Diagnosing Flea Beetle Infestations in the Garden
Mild flea beetle attacks can be spotted by closely inspecting the foliage of your garden plants. If you notice tiny round, or irregular-shaped holes or pits on the surface of the foliage. In time, flea beetle damage creates what is known as a shot hole pattern on the affected plant’s leaves, as if they had been sprayed with birdshot from a shotgun
Heavy infestations often lead to pitted areas, larger, ragged-looking holes in the foliage, leaves with areas that appear bleached, or, in the worst cases, complete defoliation, wilted plants, and stunted growth.
The larvae, which feed on the roots of the same plants that they will eventually attack the stems and leaves of, when they are adults. The damage done to the root systems by larvae, however, is usually not invasive enough to cause significant damage to the plant, or cause serious injury. Though larvae damage is not typically very harmful, there is one exception to that rule, which is the potato flea beetle larvae. Potato flea beetle larvae like to tunnel through the root system and into the tubers, which is known to cause scarring on the fruit of the plant.
Preventing and Fighting Flea Beetles
Now that you know what kind of havoc flea beetles can wreak in the garden, you more than likely want to make sure you never have to deal with a flea beetle invasion. Or maybe you’ve just learned, after reading the section on identifying these garden pests, that the bugs you’ve noticed here and there while working with your plants are flea beetles that need to be addressed before they cause a serious problem. Either way, you’ll need to learn about both how to prevent a flea beetle problem from happening in the first place (or keep it from recurring) and how to fight these pesky buggers off if they do strike. We recommend this because if your prevention methods fall through and flea beetles take hold, you’ll be best equipped to take quick action if you already know what to do—and if you already have a flea beetle problem, once it’s handled, you’ll need to roll out a prevention regiment to make sure the insects don’t return to finish what they started. The instructions below will help you keep your plants healthy and ensure your garden is safe from flea beetle damage.
Whenever possible, make your life easier by choosing resistant cultivars.
When you’re shopping for seeds and young plants, look for those labeled as resistant to flea beetles. (This information may appear on the seed packet or in product descriptions for online purchases.) Resistant plant varieties are naturally exempt from struggling with flea beetle attacks, which means you won’t have to be as vigilant in watching for the insects and you won’t need to keep up with a preventive treatment routine.
Be picky when you move transplants to the outdoor garden, adding only the best specimens to your permanent collection.
Because flea beetles are at their most detrimental when plants are young, the transplanting stage is a vitally important chance for a gardener to make a big difference in whether their plants will struggle with flea beetles. Choose the largest seedlings for transplanting, those that are in the best health. That way, if flea beetles do come knocking, your young plants will be better equipped to fight them off. Once your transplants are settled into their new location, watch them carefully with the symptoms of infestation in mind so you’ll notice a problem at the first opportunity.
Row covers over especially susceptible crops will keep flea beetles at bay.
Whenever you have a plant type in your garden that tends to struggle with flea beetle infestations more than others (in other words, when you grow the plant varieties that are often referred to as “susceptible”), you can protect these plants with row covers so flea beetles won’t be able to even make contact. Experts specifically recommend using row covers when you’re growing eggplants or to defend seedlings of any plant variety. When you target the crops that flea beetles find most attractive, you’re reducing the likelihood that any of the plants in your garden will have to deal with the stress of a flea beetle problem. Remember, once a single plant in your garden is infested, the surrounding plants are all at risk as well.
Adjust your planting schedule to minimize the possibility of flea beetles in the garden.
You can reduce your chances of dealing with a flea beetle problem to almost nil with this method.Even better, this is an easy option to roll out because you’ll be doing the work of planting anyway—simply changing the date your plants go into the ground creates no additional work for you. And unlike many of the prevention and treatment methods we’ll discuss, once you’ve executed this plan, you don’t need to keep putting in work to maintain its benefits. Flea beetles are most common at the beginning of spring, so the farther you can push back your sowing or transplanting date, the better off you’ll be when it comes to avoiding a flea beetle problem.
Just make sure to keep in mind the weather forecast for your USDA Hardiness Zone, most importantly the projected frost and freeze dates. You’ll also need to brush up on the temperatures your plants can tolerate and their maturation periods.
Choose a date you feel certain the weather will be safe for your plants, or for those without a harvest, a good date to be their last in the garden. (Of course, unless you’re a soothsayer or the Oracle of Delphi, it won’t be possible to predict the weather with 100 percent accuracy, so don’t stress about being perfect here as long as you use a responsible level of caution to select your plants’ end date.
Using the longest average available for your plants’ maturation period, work backward from the date you selected earlier to determine when you should sow or transplant your collection for the season. In other words, start with the end date or harvest date you selected and subtract the number of days in the longest maturation period your research uncovered. The resulting date is the latest date you should add new plants to your garden to avoid flea beetles. When you’re finding the necessary figures, make sure to distinguish between maturation periods for plants you grow from seed and those grown from transplants or young plants.
Weed in and around your garden meticulously to avoid providing flea beetles with free housing.
In addition to or instead of setting up shop in your garden, flea beetles can make invasive weed plants of several species their habitat if they choose. It can be baffling to have a rigorous prevention system in place against flea beetles and still see signs of their damage in your garden, with the bugs themselves nowhere to be found. If your garden has weeds sprinkled among your plants here and there or weeds occupy the surrounding area, flea beetles might just decide to make the weeds their base of operations and perform raids on your garden whenever they get hungry. Set a day of the week to be your weeding day, and really work methodically and carefully so that no alternate habitats are available for the flea beetles that can do such damage to your plants.
Do a cleanup each winter to make your garden a less attractive overwintering spot for flea beetles.
Flea beetles spend their winters in the gardens they infest, taking shelter in the soil and on plant debris. There’s not much you can do about the soil. (Hard to garden without soil, isn’t it?) But by removing the debris from plants that host flea beetles, you’re reducing the chance that the insects will decide your garden is the best place for them to spend the winter. Schedule this gardening chore for the bend of fall or very start of winter to really discourage flea beetles from staying on your property. Make sure to check the surface of the soil for foliage, twigs, and other material from the plants flea beetles prefer as well as sifting through the top few inches of soil to check for any remaining roots from these plants. Bonus: you’re simultaneously improving your soil’s drainage and air circulation for the next growing season.
Whenever possible, choose shady locations for any susceptible plants you add to the garden.
At planting time, identify any plants that will be at risk for flea beetle damage. Then take a look at the care and maintenance needs for those plants to determine whether you can get awaY with situating them in shady parts of the garden. Flea beetles love to frolic in the sun while they gluttonously devour your precious plants and trample their potentially disease-ridden feet all over your garden. When you place susceptible plants in the shade, they instantly become far less attractive to these sun-loving insects, and the bugs may decide to bypass your plants entirely in favor of sunnier accommodations and dining opportunities.Of course, some plants can’t be grown in the shade at all, so this technique can’t be used with every susceptible plant.
Whether you grow susceptible plants, your garden environment has battled flea beetles in the past, or you’re just exercising caution because you’d like to avoid the trouble these insects can cause, now you should be ready. If flea beetles want war, you’ll be armed with the knowledge you need to defend the plants that count on you for their care. But the best case scenario is for the preventive controls we’ve outlined here to work and stave off flea beetles for good. Whatever the future has in store, you can count on us to guide you through your gardening questions and prepare you to grow your best garden yet this season.