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Spokane, Washington  Est. May 19, 1883
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In the Garden: Flea beetles a recent problem for area gardeners

Flea beetles cause a great deal of damage to many vegetable crops, including beet family crops, eggplants and cabbage family crops such as this kale plant.  (By Susan Mulvihill/For The Spokesman-Review)
Flea beetles cause a great deal of damage to many vegetable crops, including beet family crops, eggplants and cabbage family crops such as this kale plant. (By Susan Mulvihill/For The Spokesman-Review)
By Susan Mulvihill For The Spokesman-Review

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 new 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.

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 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.

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) and nightshade family members (eggplants, peppers, potatoes, tomatillos, tomatoes).

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

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 – with the exception of beets, radishes and turnips – can be started indoors ahead of time. By doing this, the plants will be healthy and 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, it’s difficult 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.

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