Sept. 5 Column: Flea Beetles

If you just groaned when you read the title of this post, I completely understand! Dealing with flea beetles in the garden is extremely challenging. That’s why I’ve focused on them for today’s column. You can read it online in The Spokesman-Review: Flea beetles are a recent problem for area gardeners. (or you can start reading it underneath my video below)

Here’s a true story. I’ve been a Spokane County Master Gardener for nearly 20 years and a columnist for about 15 years. Yet I’ve never been asked questions about how to control flea beetles. That led me to think they don’t exist here in the Inland Northwest. Well, until last year, that is!

Suddenly, folks asked me to identify the bugs and give them ideas on how to control them. Hmm, what changed? One of the persons who contacted me is fellow Master Gardener Marcia Sands. She had a neighbor who was having a terrible time with them last summer. After visiting that gal’s garden — and another person’s garden — I realized flea beetles were becoming a “thing” here. Yikes.

Marcia became concerned as well, so she polled the rest of the Master Gardeners. It turns out many of them were dealing with flea beetles for the first time. That is NOT good news at all! Fortunately, I was in the process of researching for my book, The Vegetable Garden Pest Handbook. That means I had a lot of information at my fingertips.

OK, back to my column. You will learn about their life cycle and the vegetable crops they bother the most. I also explain the easiest thing to look for when trying to determine what the pest is. Then I go through different organic strategies and products that are effective at controlling them.

So far, I haven’t had them in my garden and I’m hoping to keep it that way. But I also realize we gardeners don’t always get to dictate what our challenges will be! One thing Marcia and I couldn’t find was a common denominator to explain the sudden appearance of flea beetles in Spokane. That was frustrating. I hope you’ll find my column useful, though.

For this week’s video, I decided to tackle a timely topic: when to harvest winter squash and pumpkins. There are signs to look for and a simple test to determine ripeness. I also want to mention this: don’t be in a huge hurry to harvest them. The only exception is if you have a really bad frost coming your way. Winter squash and pumpkins benefit from having lots of time to grow.

Garden column on flea beetles:

Many vegetable bugs are fairly straightforward to control but others are downright challenging. Flea beetles fall into the latter category.

When I was doing the research for my book, The Vegetable Garden Pest Handbook, I knew flea beetles are a huge problem in many parts of the country. In my nearly 20 years as a Spokane County Master Gardener, I have never been asked for suggestions on how to control them so I figured they must not be a problem in this region.

That changed when two local gardeners reported that very problem last summer. One of my colleagues, Marcia Sands, was also surprised to hear about this. She sent out a quick survey to other Master Gardeners to learn if they were suddenly having to deal with this pest. Several reported they’d had them in their gardens for the first time ever.

Description of Flea Beetles

Flea beetles are tiny black or brown insects between 1/16 and ¼ inch long. They use their strong hind legs to jump off plants and out of harm’s way. They can fly as well so they are difficult to catch.

The adult female lays eggs in the soil near a host plant. After hatching, the larvae chew on the roots. They go through the next stage of their lives as pupae within the soil before emerging as adults. Some pupae also overwinter in plant debris, emerge in the spring, mate and start the whole cycle all over again. Of the different stages, the adults cause the most damage.

Because they’re so small, it can be difficult to spot them on your plants but there is one telltale sign that is unique. They chew tiny holes in the leaves, which are referred to as “shotholes” because they give the appearance of having been fired at with a shotgun.

Which crops do flea beetles bother?

Flea beetles target a lot of vegetable crops:

• Artichokes
• Beet family members (beets, spinach, Swiss chard)
• Cabbage family members (arugula, broccoli, cabbage kale, kohlrabi, mustard, radishes, turnips, etc.)
• Nightshade family members (eggplants, peppers, potatoes, tomatillos, tomatoes)

If you notice shotholes in plant leaves or wilting plants, take a close look. You’ll want to leap into action if you see flea beetles. Here are some strategies you can employ:

Strategies and products for dealing with flea beetles

Be sure to clean up plant debris this fall to eliminate potential overwintering habitat.

Give your plants a headstart in the spring. The majority of the plants listed above can be started indoors ahead of time. The exceptions are beets, radishes and turnips. By doing this, the plants will be healthy. That means they’ll be better able to withstand insect damage when they are transplanted outdoors.

Confuse flea beetles by using reflective silver mulch. This sheet mulch is so bright and shiny. That makes it hard for them to find your plants if you cover the surface of your planting bed with it. Cut slits or small holes to plant your seedings. Once the plants’ foliage covers much of the mulch, it won’t be as effective. But the good news is your plants will have gotten off to a strong start.

Use floating row cover to hide your plants. Even if your seedlings will eventually need to be pollinated, you can cover them right at planting time to protect them. The row cover will act as a physical barrier to keep flea beetles away from the plants. Once they begin blooming, remove the cover.

Organic products such as diatomaceous earth, kaolin clay or spinosad are effective controls.

Susan Mulvihill is author of “The Vegetable Garden Pest Handbook.” She can be reached at Susan@susansinthegarden.com. Watch this week’s “Everyone Can Grow a Garden” video at youtube.com/susansinthegarden.