7 Natural Ways to Control Cucumber Beetles


Striped and spotted cucumber bugs

So far the 2014 garden is off to a great start! At the end of May I shared a summary of what’s going well and what’s not-so-swell. At that time, the garden remained relatively pest-free. However in the short time since that post I’ve encountered to more prevalent invaders. The first pest is a mysterious, large, picky eater. The invader may be a deer, although there are no signs of jumping our 8-foot tall fence and the tracks left in a few places seem a bit large for a deer. (Unfortunately between rain and very soft soil the shape has been difficult to determine.) Whoever has been helping themselves has passed over scores of deer-favorite veggies in favor of our kale and pepper plants, exclusively.

Meanwhile, our other main invader is not nearly as elusive or picky. This year I’ve experienced the earliest and most prolific invasion of cucumber beetles ever. They have recently backed off without intervention from me, so I’m hoping the garden will be able to weather their presence without any (natural) chemical or other intervention from me. Though they have impacted several different crops, so far the only casualty has been my acorn squash (wiped out almost entirely). Fortunately there’s plenty of time left in the Michigan growing season to reseed squash. Just in case you’ve also encountered a cucumber beetle invasion, here’s some information and a few tips for letting them know who’s boss!

What Are Cucumber Beetles?

According to our buddies at Wikipedia:

“Cucumber beetle is a common name given to members of two genera of beetles, Diabrotica and Acalymma, both in the family Chrysomelidae. The adults can be found on cucurbits such as cucumbers and a variety of other plants. Many are notorious pests of agricultural crops. The larvae of several cucumber beetles are known as corn rootworms.”

Cucumber beetles actually look like cute little yellow lady bugs. (They had me completely fooled during my first year as a CSA grower!) Don’t be fooled. These little guys want to eat your cucurbits to oblivion. That means they’ll feast on cucumber, pumpkin, zucchini and hard squash plants, to name a few. They also appear to be nibbling on my beans and possibly my ground cherries.

Here is a description from the Farmers’ Almanac to help you identify cucumber beetles:

“Adults are about ¼ inch long and have a yellow and black striped abdomen and a dark colored head and antennae. Look for holes and yellowing and wilting leaves. Crop yield will be low; and plants will produce yellow and stunted fruits. The larvae are worm-like, white, dark-headed, a have three pairs of legs on the thorax.”

Transforming leaves into swiss cheese (or gobbling them up entirely) aren’t the only ways cucumber beetles wreak havoc in a garden. They are also carriers for diseases such as bacterial wilt and cucumber mosaic virus.

Cucumber beetles overwinter in plant debris and wooded areas near your garden. Once temperatures warm, they can move into the garden to begin feasting on your newly transplanted seedlings. While the adults can eat leaves, stems and blossoms, the larva will also feast on the plant’s root system.

How to Control Cucumber Beetles

Here are some natural (or at least, free from synthetic chemicals) methods you can use to address cucumber beetles in your garden.

1. Plant Late

One of the best things you can do to avoid a cucumber beetle infestation is to plant later than normal in the season. The adult bugs will come out of hiding in spring, looking for food. If you wait until the end of June or early July (in Southwest Michigan) to plant, they may have already given up on your space and taken up residency in someone else’s garden. I have found this to be a very effective method for growing yellow squash. (It works with squash bugs too!)

2. Use Row Covers

Using a floating row cover or a cover on hoops acts as a barrier to keep beetles from reaching your plants. If you use this method, remember that you’ll need to uncover blossoming plants for several hours during the day in order to allow pollination. And in the case of row covers, you’ll also need to ensure proper ventilation to avoid the buildup of excessive heat and moisture (thus increasing the chances of developing a mildew issue).

3. Kaolin Clay

Kaolin is a clay mineral, usually white, that occurs naturally from the breakdown of rocks in hot, wet climates. When used as a spray (powdered kaolin clay mixed with water) it deters pests because it makes their bodies sticky and has an unpleasant taste. The whitish film left from this spray has no known toxicity, can be sprayed even onto fruit (and even on the day of harvest) and is easily wiped or washed away before eating.

4. Trap Crops

You can divert cucumber beetles by planting something they prefer to eat and luring them away from more prized crops. The Seed Hopper blog suggests planting Baby Blue Hubbard Squash around the perimeter of your garden or in a location that will attract the beetles away from other cucurbits. As a bonus Baby Blue Hubbard Squash tends to be less susceptible to beetle-borne diseases than some other cucurbits.

5. Sticky Traps

Think of this as fly tape for cucumber beetles. Many bugs, including cucumber beetles, are attracted to the color yellow. You can purchase pre-made traps or create your own by adding specially made glue to yellow paper or cups.

6. Remove by Hand

If you’ve got the time and it doesn’t make you squeamish, you can remove these bad boys by hand. Drop them into a cup of water with a bit of dish soap. The soap will break the tension of the water so that they take a … very deep swim.

7. Neem Oil

Neem oil is a naturally occurring chemical that is effective for addressing several plant diseases and pests. Last year I wrote a more thorough description of the uses of neem oil and you can find that by clicking here. Neem oil kills cucumber beetles on contact. It can also be used to kill eggs deposited into the soil.

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