IPM & the Colorado potato beetle

by Caroline Brown

The Colorado potato beetle (Leptinotarsa decemlineata) is one of North America's most ravenous and difficult to control garden pests. The most common potato beetle, it is serious pest to potato and eggplant crops and is often destructive to tomato crops. But it can be controlled sustainably using a combination of integrated pest management techniques and cultural, biological, chemical, and physical controls.

Identification. As seen in the photo at right, the Colorado potato beetle (henceforth known as CPB because I'm too lazy to type Colorado potato beetle a million more times) is a yellow beetle with 10 black stripes.

Larvae (2 pictures, left) are orange or red with black head and legs, and the larger ones have black spots on the sides. When mature, they're 1/2" long. Look for them on the undersides of plant leaves.

Eggs (right) are usually found on the undersides of leaves in clusters and are yellow-orange.

Cultural control. Cultural control of CPB includes standard integrated pest management (IPM) practices. The best cultural control is choosing potato varieties with the earliest maturation rates in your growing zone–the earlier your potatoes are ready to pick, the better chances your plants have of surviving beetle infestations. Some varieties that mature early are Caribe, Norland, Pungo, Redsen, Sunrise, Superior, and Yukon Gold (75 to 88 days).

CPB overwinter (as adults) deep underground. As it gets warmer, they make their way to the surface, usually emerging by spring, when they look for an acceptable food source. (Probably, if they're overwintering in your yard, that means they had an acceptable food source last season.) Then they mate and the females begin producing eggs. So, an alternate form of cultural control–if you have a long growing season– is to wait and plant your potatoes until after the population of overwintering beetles have emerged and declined.

Crop rotation (locating the crop in area each season) is another cultural solution that is not always practical for the home gardener. Although crop rotation cannot completely eliminate the pest, it can slow it down. Floating row covers (right) can keep migrating beetles from accessing your plants. Floating row covers are made of a breathable white cloth that lets light and water through (not just plain clear plastic). You can get them at most garden supply catalogs…Gardens Alive is one example. Just make sure to monitor the plants beneath the row cover to make sure that no CPB were lucky enough to get trapped inside when you put the row cover on.

Finally, mulching your potato beds with straw can help delay CPB development.

Physical control. The home gardener with a small plot of potatoes can usually pick off adult beetles, larvae, and eggs. Drop them into a bucket of soapy water or vinegar and dispose of properly.

Biological control. There are some natural parasites and predators of CPB and you might be lucky enough to have those in your yard. Natural predators of CPB include lady beetles (ladybugs), lacewings, predatory stink bugs, and certain spiders. Two species of fly, Doryphorophaga doryphorae and D. coberrans parasitize CPB larvae, and one species of wasp, Edovum puttleri, parasitizes CPB eggs. You can't count on having these in your garden, but they are a good reason not to indiscriminately spray pesticides in your garden–you'll kill the good insects too.

Bacillus thuringiensis, or Bt, a naturally occuring bacteria that is toxic to many insects, has been proven to be very effective in controlling CPB. The Bt subspecies that is effective against CPB is called the san diego or tenebrionis strain. You can buy an insecticidal spray that contains the bacterium spores, or spray the bacteria directly onto the plants. Bt alone is worth a separate post….so in the next week I'll make a post that gives more information about the different types of Bt, where to buy them, and how to apply them.

Chemical control. CPBs have developed a resistance to the hardcore chemical pesticides of our parents' gardening days–think Sevin. So even if you're tempted to douse your plants with some evil chemical—don't, because it probably won't work. However, there are some botanical pesticide options that are available, although these are the least "earth-friendly" options.

Examples include products with rotenone, derived from the roots of a certain plant, and Pyola, an insecticide made from canola oil and naturally-found pyrethrins. Botanical pesticides derived from neem tree seeds have also proven effective. Brand names are Neemix, Margosan-O, and BioNeem. Be sure to read the directions carefully before buying and applying!!

Primary Sources

Colorado Potato Beetle Organic Control Options, National Sustainable Agriculture Information Service

Colorado Potato Beetle Greenshare Factsheet, URI Landscape Horticulture Program

Photo Credits

Adult–Image from Wikipedia, courtesy of USDA/Scott Bauer

Larva–Image 1 from URI, courtesy of Dr. Richard Casagrande; Image 2 from Wikipedia, courtesy of user "Pollinator."

Eggs–Image from Purdue University, courtesy of W. Crenshaw

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15 Responses to “IPM & the Colorado potato beetle”

  1. Thanks for the informative post Caroline. I actually left a comment before this but it seems to have disappeared. WordPress is acting wonky it seems, just had problems putting a link in a post, it just can’t be me causing the problem hahahaha….

    I will print this out and keep it until garden season arrives here, that’s usually the end of May.
    Have a great day, Meow to the kitties and BFN, :)

  2. Hi Caroline, Well we finally got our potato patch sown yesterday….now to wait a couple of weeks to see them shoosting up LOL…remember Green Acres?

    I just re-read this post. do you think spraying the leaves with a water/vinegar mix OR water/dishsoap mix, might do the trick, before they start chewing on the leaves? The thought of going over every leaf, looking for eggs sounds impossible and yuccky too.
    Let me know.Hope you are having a great weekend. BFN, G :)

  3. Hi Geraldine, soap & water is OK, though I don’t know how strong it would be and you would have to reapply after rains. I wouldn’t do vinegar & water though! I only use vinegar on plants I want to kill like weeds. :) You might try the Pyola. I think you can get it at Gardens Alive.

  4. Thanks again. Is dishsoap ok? Do you need to add much to the water? Might be kind of interesting if it DID rain LOL….. bubbless.sssss…. G.

  5. yah, dishsoap is A-OK! Guess if you over did it your garden would look like a dishpail when it rained!

  6. nothing like really clean veggies!!!!! LOL

  7. My Jack Russell was barking furiously at something on the back porch. There was a snorting sound – or something similar to heavy breathing in spurts. When I finally retrieved my Josie from the area, lo’ and behold it appeared that she was hot on the trail of what I now think is a potato beetle. Of course, I captured it in a jar because it’s necessary to study to find out what the culprit is – call me wierd. Then I immediately searched the net and came up with your site. Wonderful! Do potato beetles make a snorting sound? We live in NM – and there are no flowers or veggies near by, so I’m wondering if this is indeed the potato beetle. Thanks for your help.

  8. Hi Sheryl, your Jack Russell is one of the best examples of earth-friendly pest control that I’ve heard of so far. :) I’ve never heard of a potato beetle snorting, but I’ve heard of beetles that hiss, squeak, and click. So I suppose anything is possible!

  9. yes the water and vinigar mix will work i have done it on my own plants and it sems to work beautifuly so far. glad i could help! :) BFN David Cook

  10. hey sheryl, the potato beetle does hiss. We found one out on our boat and we touched it and it hissed at us.

  11. i found some!! ladybugs eat there eggs!!

  12. i found some in my garden then found out that ladybugs eat there eggs!!

  13. I live in Maine and we have the Colorado Potato Beetle in mass at our small garden. They have eaten the entire leaf from the potato planting and are now moving to the Pumpkin Patch. Does anyone know how severe they will be to the pumpkin leaves and vines? We have only picked and used soapy water for disposal of the picked beetle. I’m not sure what I can put on the pumpkin patch. Will soapy water hurt the leaves or vines?
    Thanks much

  14. Just found theese little buggers on my egg plants, they seem fond of sunflower leaves too.

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