The Colorado potato beetle (Leptinotarsa decemlineata) is by far the biggest pest for both backyard and commercial potato growers. These tiny beetles with orange and black stripes are prodigious breeders, and each female can lay up to 25 eggs at a time. Once the eggs hatch, the larvae do the majority of the damage to potato and other nightshade plants, peppers, eggplant and tomatoes, while satisfying their voracious appetites.
As many gardeners soon realize, these beetles are extremely difficult to get rid of. They have adapted a resistance to most control methods, both conventional and organic. As a result, your best weapons for dealing with the Colorado potato beetle are vigilance and speed.
Best Practices for Protecting Plants
Preventing an infestation in the first place is easier than treating one that has already occurred. Protect your potato crop from beetles by trying a few of these methods together, especially if you've had a problem with potato beetles in the past.
Don't grow potatoes in the same spot year after year. The adult potato beetles overwinter in the soil of the previous year's potato patch. If you plant in the same spot as last year, you're giving the beetles convenient access to your plants. They'll pick a plant, find a mate, lay eggs, and the cycle will continue.
There are several plants that deter potato beetles. Try planting at least one or two of them alongside or even interplanted with your potatoes. A few good options include catnip, tansy, and sage. Be aware that catnip and tansy can spread easily. You can keep them in check by not letting them go to seed and pulling any unwanted young plants right away. Several varieties of sage are pretty good about staying in place.
Mulching heavily with straw not only helps keep the tubers out of the sunlight but also creates a habitat for predators of the Colorado potato beetle. If you can attract ground beetles, ladybugs, and green lacewings, they'll do a lot of the hard work for you.
Resistant or Early Plant Varieties
Certain varieties of potatoes, such as Russet Burbank, have proven to be resistant to potato beetles. Another good practice is to plant early varieties since potato beetle damage only gets worse as the season goes on and all the eggs hatch. Consider planting Caribe, Norland, or Yukon Gold potatoes; these are all great early-season options.
Organic Treatments for Colorado Potato Beetle
There are a few methods that work well against potato beetle once plants are infested. They all require that you pay close attention to what is happening in the garden and act quickly. If you can start combating the beetles as soon as you see evidence of them you have a better chance of saving your potato crop. Effective organic controls include treating with insecticidal oil and removing the bugs manually.
- Apply neem oil as needed. This is the organic gardener's go-to insecticide, and it works wonders––even better than most conventional options.
- Hand-pick beetles, larvae, and eggs and throw them in a bucket of soapy water to kill them. Regularly check the undersides of your potato leaves for eggs and larvae which are a distinct yellow in color. If you spot an adult beetle among your plants, you can be sure to find larvae as well.
- Adult beetles return to burrow under the soil at night around the base of your nightshade plants. Look for them there early in the day and toward the top of the plant later on as the beetles move toward the newest freshest and most tender leaves.
- Use a vacuum to remove beetles, larvae, and eggs. There are special "bug vacs" for garden use, but a regular household handheld vacuum also works well.
- Keep in mind that beetles, which generally have a hard carapace, are best treated with contact deterrent sprays when they are still in the larval stage and soft-bodied.
Colorado Potato Beetles in Home Gardens. University of Minnesota Extension Website