A Simple Way of Thwarting Potato Beetles


Here’s a simple, but effective way of keeping one pest out of your plants!

To avoid the Colorado potato beetle, Leptinotarsa decemlineata, an insect with a worldwide distribution that decimates the leaves of potato plants (Solanum tuberosum) and can severely hinder their production, just plant your potatoes not in the vegetable garden, all grouped together, but in the flower bed, scattered here and there among the other plants.

Many varieties of potato bloom readily and produce pretty flowers, so fit well into a flower bed. Photo: Keith Weller, Wikimedia Commons

Adult Colorado potato beetles are attracted to potato plants by the distinctive odor of their foliage and find their host more readily when the potatoes are planted in dense rows, as in a vegetable garden, concentrating the smell. But when the potato plants are scattered among other plants, especially plants with distinct odors of their own (and many ornamental flowers appear highly scented to insects), the problem largely disappears. They just can’t find their host plant!

Sometimes one or two of the second generation of potato beetles manage to find the potato plants in midsummer, but they won’t have time to do much damage: the production of tubers will be well under way by then and they won’t really hinder potato production. Just pull them off and squish them if their presence bothers you.

The following year, repeat the same treatment … applying crop rotation by planting that year’s potatoes in different spots than the previous year.

Thanks to your cunning planting, you’ll soon become the potato beetles’ worst enemy!

Confuse Insects by Avoiding Monocultures


MonocultureTo reduce the risk of insect infestations, it’s best to mix vegetables in the garden rather than grouping them together.


Colorado potato beetle

For example, growing potatoes in a row is almost an open invitation to the Colorado potato beetle to come to dinner, as when any vegetable is planted in dense quantities, the smell it gives off (undetectable to humans, but very obvious to its primary insect pests) is concentrated, attracting its enemies. But if you plant your potatoes here and there among other vegetables or in the flower garden, its beetle enemies will have a hard time finding them.

It’s the same thing for carrot fly, tomato hornworm, even vine weevil. Mixing things up at planting time results in fewer insect attacks.

That’s why is it best to avoid “monocultures” (cultivation of a single vegetable over a large area). With a diversified, mixed vegetable garden, your plants will suffer from far fewer insect pests.

Since I gave the Colorado potato beetle as my main example and it is indeed one of the more difficult insects to control, here are a few other suggestions on how to prevent and treat them.

Controlling Potato Beetles



Adult potato beetles.

The Colorado potato beetle (Leptinotarsa ​​decemlineata), also called the potato bug, is essentially specific to the potato plant, at least in our gardens. Although it can theoretically also attack the foliage of other plants in the Solanaceae family, such tomatoes, peppers, daturas, petunias and others, it almost never does.

At this time of the year, you’ll soon be seeing the adults popping out of the ground and chowing down on the leaves of your potato plants, if indeed they’re not already present. And although the pest was originally limited to the Rocky Mountains (whence the name “Colorado”), it is now widespread across North America, Europe, and Asia: wherever potatoes are grown.



It is a very easy insect to recognize: it’s a rounded beetle, much like a giant ladybug, but yellow with 10 black stripes rather than being spotted like true ladybugs. The larvae are orange marked with black points. Since each female can lay up to 800 eggs, it is very prolific!

Controlling the Colorado potato beetle is very difficult… unless you stop growing potatoes! Many community gardens have learned this and have banned potatoes from their lots. They have learned from experience that gardeners struggling with potato beetles will stop at nothing in trying to control them and tend to treat their potatoes with particularly lethal pesticides, which in turn provokes the ire of neighboring gardeners less accepting of poisonous insecticides. So they ban potatoes all together, allowing everyone to garden in harmony.

That’s a valuable life lesson the laidback gardener should consider: no potatoes, no beetles. Problem solved! You simply have to go buy your potatoes in the supermarket like everybody else.

But if you really want to grow potatoes in spite of the need to control the Colorado potato beetle, here are some tips to help you.

Prevention is Better than Cure


Floating row cover.

First, if the beetles are not yet present on your plants, you can keep them off by covering them with a floating row cover securely fixed to the ground. Water, air and sunlight can penetrate this barrier, but not the beetles.

For this technique to work, though, it is essential that you carry out crop rotation. In other words, you have to have planted your potatoes in a section of garden where there were no potatoes the previous year. If not, when the beetles emerge (they spend the winter in the soil at the foot of last year’s potato plants), they won’t be excluded by the barrier, but instead trapped inside it… where they can enjoy a scrumptious potato leaf meal safe from your efforts to control them!

The Horse is Out of the Barn?

If the beetles have already arrived, try one of the following treatments:

• Pick hand adults and larvae and crush them or drop them into soapy water. Or, in the case of larvae, just knock them to the ground, as at that stage they don’t have the ability to climb back onto the plant;

• Run a hand vacuum over the foliage to pick up both adults and larvae;


Potato beetle eggs.

• Search and crush the orange eggs found beneath the leaves

• Liberate Asian ladybugs (predators on potato beetles) on your potato plants and hope they don’t all fly away;

• Spray regularly with appropriate insecticides (pyrethrin, neem, etc.);

• Treat with BTT (Bacillus thuringiensis tenebrionis)… if you can find it. This is a natural bacteria specific to Colorado potato beetles that will kill them if applied correctly. Note that this is not the usual BT found in garden centers. That is BTK (Bacillus thuringiensis kurstaki), specific to caterpillars, not beetles. Nor is it BTI (Bacillus thuringiensis israelensis), sold to treat mosquitoes. Unfortunately, BTT (“potato beetle BT”) is not widely available. In Canada, it’s not available at all; you’d have to import it from the USA.

• Finally, the second most laidback trick for controlling potato beetles (the first being not to plant potatoes at all) is to plant your potatoes not in rows, which simply concentrates the scent that attracts potato beetles, but here and there among your other vegetables. That way potato beetles often can’t even find your plants!