How to Control and Eradicate Flea Beetles | Gardener’s Path

Shot-holing is a collection of small pits and holes that the insect chews out of the host’s leaves.

Young and recently transplanted plants are particularly susceptible. For the fastidious gardener, this little beetle can cause a lot of frustration!

Just in case the above-ground damage wasn’t scary enough, I’ll continue. Below ground, the larvae feed on the roots and tubers of host plants.

Notable is the damage suffered by potatoes from this insect, resulting in grooves marking the surface or small holes in the skin and outer flesh.

Last spring, my husband I planted the most perfect potato patch. We patiently waited while the precious spuds grew.

We noticed some small holes dotting the foliage, but nothing too alarming (we thought…).

Dig day arrived, and to our great annoyance, our spuds appeared to have been poked by a ballpoint pen, with dark holes spotting the otherwise beautiful tubers.

Though imperfect produce is often just as delicious as a potato or tomato with a pristine skin plucked from a plant with unnibbled leaves, do you really want to share those crops with the neighbors?

I didn’t think so. So it’s time to get rid of those bugs!

Organic management methods may be employed to combat these pests through cultural, physical, and organic-approved sprays and drenches.

Identification, Biology, and Distribution

The flea beetle is approximately 1/16-1/4 inch long, depending on the type. Its segmented back legs are long, giving it the ability to jump.

And it is also adept at flying. There are numerous species, and their colors vary widely depending on the region where they are found.

The beetles come in some very fancy colors including black, greenish-black, brown, metallic, white-striped, or yellow and orange striped.

Don’t be fooled. Develop a keen eye for spotting these pests, so you don’t have to suffer the devastation of their less-than-creative artwork on your plants’ leaves and tubers.

See the table below to identify some common cruciferous feeders (cole crops like cabbage, kale, and Brussels sprouts) versus solanaceous feeders (nightshade family including tomatoes, potatoes, and eggplant).

These insects identify their feast (read: host plant) based on smell and visual indicators – much like we do!

Flea Beetle Types

Life Cycle

Adult beetles overwinter in the soil, leaf debris, or grassy borders of the garden or field. At just about the same time when we begin to emerge from our homes in springtime, so do they. As temperature warm, they get busy.

Adults find a healthy host and begin chowing down after a long winter’s nap. Following a hearty meal, the beetles lay their eggs at the base of the host plant.

These eggs will hatch in approximately 10 days, hatching out into small whitish larvae measuring between 1/8 and 1/4 inch long, with dark heads and tiny legs behind.

They are less cute than they sound.

Freshly hatched larvae feed on the roots of plants for the next three to four weeks.

Following this period, they pupate for approximately 7-10 days before surfacing to indulge above ground. In warmer regions, multiple generations may occur each year.

And that’s likely to cause a problem in your vegetable patch, unless you take action.

With some careful planning, preventative measures, and an action plan in place, you won’t have to worry about the safety of your precious broccoli and eggplants.

Damage Caused

Don’t wait until it’s too late!

The flea beetle may cause significant damage to the roots and foliage of your plants. Scouting twice a day for these pests is a good practice in an organic program.

I like to set an alarm on my phone to remind me to check the garden twice during the day.

I grab a little gardening journal that I keep by the back door and trot to the garden for a quick scouting session. I take notes and pictures of what I see, so I will have a record.

This really doesn’t have to take more than a few minutes to accomplish, depending on the size of your garden.

Watch for holes that have been chewed into the leaves by adult flea beetles in the pattern of buckshot, or a messy lace pattern.

To scout for larval damage, check the roots of a few plants or the tubers of potato plants to look for the whitish larvae munching away, or furrowing grooves in your tubers.

If you’re like me and can’t stand the thought of sacrificing a few plants, you can dig down next to the plant, gingerly move the dirt to the side to take a look, and replace the dirt afterwards.

Be vigilant. If you do have an infestation, take action immediately to avoid further damage, and to remediate this threat to the health of your plants.

Organic Control Methods

There are a variety of methods for controlling these pests, including cultural, physical, and biological.

Cultural

You can often avoid an infestation altogether with some cultural controls.

Planting Schedules

Planting earlier than adult flea beetles become active in springtime can give your plants a head start on the season. And who doesn’t like a good head start?

Plant well hardened-off transplants as soon as the threat of frost has passed in your region.

Another record-keeping tip: If you aren’t keeping a gardening journal already, start one. Record when you plant your first transplants, and when you spot your first beetle.

You have no idea how much this will aid your planting schedule design and pest management routine in years to come (or maybe you already do have some idea, and you just need an extra push to put pen to paper – you’re welcome!).

You may also consider planting your brassica crops later in the summer, when the adults are getting sleepy from all of their summertime feasting and going dormant.

Sanitation

Being diligent about keeping your garden clean and free of too much debris may help to keep pest pressure at bay.

I use the same (okay, maybe a little looser) rules in my garden as I do in my bathroom:

A little cleanup each day keeps the unwanted guests from taking up house. Do your best to keep tall weeds and old piles of leaves out of the garden where these insect pests may overwinter.

Till the Soil

This is a cultural method implemented by many, especially in the spring and fall.

This method is a little gruesome for my taste, but if it’s unwanted pests or my potatoes and broccoli, the choice is a little easier to make.

Tilling in the spring kills the majority of overwintered beetles, while tilling later in the season destroys larvae and cleans up the garden before fall, interrupting the adults’ overwintering patterns.

Though tilling may help with immediate management, its long-term benefits may not be as effective as other cultural management methods – especially if you subscribe to no-till methods and believe in promoting a healthy microbial ecosystem and applying helpful soil microbes.

I am personally of this camp. You can read more about the benefits of a no-till garden here.

Trap Crops

A trap crop acts as a decoy for the main crop. Plant your trap crop before your main crop so that the insects are attracted to your trap crop first. Sacrificial, but usually effective!

If you spot flea beetles in your trap crop, consider spraying or dusting (depending on your chosen method of management) to control the population and keep them from migrating towards the main crop as the trap crop becomes less desirable.

Some recommend tilling under the trap crop once it becomes infested, but this could create a dangerous situation wherein the main crop becomes the primary target.

Some good trap crops include radishes, giant Chinese mustard, collards, and bok choy. The idea is to provide a tempting treat for the insects so they will focus on the trap crop instead of the main crop.

Plant your trap crop around the perimeter or in between rows of your main crop for best results.

Read more about planting and using trap crops here.

Legumes like clover and vetch act as fantastic living mulch between rows, or under-sown. However, do note that living mulches will compete with the main crop for water and nutrients.

Non-living mulches can interfere with the adult flea beetle’s egg-laying. A few options for non-living mulches that I prefer are barley straw and leaf litter.

Keep in mind that it is important to clear these mulches out at the end of the season to prevent providing a perfect overwintering space for adult beetles.

Transplant Large Seedlings

Transplanting seedlings that are mature and large is another excellent way to combat flea beetles.

Older transplants may resist pest pressure and recover more quickly if they suffer damage.

Transplanting puny starts (read: baby plants) essentially sends an open invitation to the the transplant’s predators: “Pick me! I’m weak and ripe for the eating!”

A transplant goes through a lot of stress when it is transitioning from its first home, the starter flat that you carefully planted in your guest room or brought home from the garden center, to its permanent spot in the garden.

The healthier it is, the greater chance it has of successfully surviving the big move.

Sticky Traps

These traps may be used to trap insect pests, but their real value comes in helping to scout and identify the insects living in your garden.

Some traps are designed to actually combat pest pressure by attracting and catching specific insects, to keep them from eating your plants.

But usually – and specifically for flea beetles – they are used as a tool for you to more easily get to know who the unwanted visitors are to your garden.

Traps act like low-tech security cameras!