The Unique Challenge of Colorado Potato Beetles

It wasn’t until about 150 years ago that Colorado potato beetles began to play such a dramatic role in potato production in the US. Before then, this harmless insect fed on a handful of weed species in the foothills of the Rocky Mountains. As the first pioneers brought potato production to the western territories, the potato beetle found a new source of food. This pernicious pest migrated eastward along the routes of the pioneers, reaching as far as the East coast by 1874.

Most of us are bitterly familiar with the Colorado potato beetle and the rampant destruction which it can cause. This dome-shaped insect is easily identified by the five black stripes on each yellow wing cover. Adults overwinter deep in the soil and emerge in late spring with a fierce appetite. Upon emergence, potato beetles travel on foot for several days and sometimes over a mile to seek out a food source. While they predominantly feed on the tender leaves of young potato plants, all members of the nightshade family (potatoes, tomatoes, eggplants, peppers, tomatillos) are at risk.

The female Colorado potato beetle can lay up to five hundred bright yellow-orange eggs in clumps of 15-25. From these eggs hatch the larvae, which do the most damage to foliage. These larvae resemble plump orange grubs and feed for 2-3 weeks through four stages of molting, finally crawling into the soil to pupate. Here in the Northeast, a second generation emerges after a brief resting period. Regions south of here experience yet a third generation before adults go into hibernation in late fall.


Organic Methods of Controlling Populations

As damage to potato crops has grown ever greater, farmers have employed a multitude of synthetic pesticides. Given its rapid rate of reproduction, the potato beetle developed resistance to many of these pesticides, resulting in more regular spraying of the most persistent chemicals. Most organic growers take a multi-faceted approach to control of the Colorado potato beetle.

Prevention. Organic control of the Colorado potato beetle depends greatly on cultural practices, the most important of which is crop rotation. Moving host plants to a new location can cut populations significantly as they struggle to find a viable food source in the springtime. As I mentioned above, post-emergence adults are known to travel great distances, but every little bit helps. Barriers such as rivers or roads between fields can help to amplify the effect of rotation.

Physical exclusion is best achieved by lightweight row cover set over potato plants before the beetles arrive in the spring. Early placement and well-sealed edges ensure that any hungry beetles cannot reach young plants. Using straw mulch around the base of plants after an early hilling has been shown to be an effective measure of exclusion as well. The mulch makes it harder for beetles to find potato plants, as well as creates an environment that favors natural predators.

Trap Crops. Many growers use traps as borders for their potato crops. The most common of these is a wide ditch dug around the perimeter of a potato field. This ditch is steep on both sides and is lined with black plastic. Since the beetles can only walk after emerging from hibernation, they must cross this ditch, where they slip on the steep sides and reach their timely demise under the hot sun.

Physical Removal. Many potato growers resort to picking adult beetles off by hand, killing one at a time by drowning or crushing them. Squishing the orange egg deposits on the undersides of potato leaves is a great way to efficiently extinguish the next generation. For obvious reasons, this tactic is only practical for small scale producers and home gardeners.

Flaming has become more popular in recent years as the equipment has become a bit more polished. This must be done as the adults first inhabit the plants and on a sunny day while the beetles are active on top of the foliage. The young potato plants will be able to recover from a brief exposure to intense heat, but the beetles will not.

Organic Pesticides. In recent years, a strain of the naturally occurring Bacillus thuringiensis bacterium has been touted as an organic alternative to these dangerous synthetic pesticides. While this is certainly an effective organic treatment, it should be cautioned that the development of resistance remains a concern whenever we rely heavily upon a single class of pesticide for control. There are a multitude of bio-insecticide brand names in which B.t. serves as the active ingredient.

Here at High Mowing, we know the frustrations that these guys can cause—the past two years we’ve worked hard to protect our small potato crops so those tricky potato beetles they have instead found and decimated our eggplants all the way back to the stems.  It can feel dire sometimes—and I assure you that picking potato beetle larvae and squishing eggs is not among our favorite summer activities—but it’s a good reminder of how it pays off to maintain diligent scouting, take immediate action, and always start out with healthy plants that will be more likely to be able to bounce back after significant damage.

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23 Responses to The Unique Challenge of Colorado Potato Beetles

  1. Introduce beneficial insects into your garden. Ladybug beetles and stink bugs are effective in getting rid of Colorado potato beetles, especially when the infestation is not severe.

  2. Pingback: Organic Control Colorado Potato Bugs | Cure for Pcos

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  7. Pingback: What’s Wrong with My Garden? Part 1: How to Manage Common Insect Pests | High Mowing Organic Seeds' Blog – The Seed Hopper

  8. Jane Loomis says:

    We hand pick the adults and grubs and tear off the parts of any leaves that contain egg masses, dropping them into a 5 gal bucket with an inch or so of soapy water. Removing the egg masses stops the next generation. Removing the grubs obviously cuts way down on the damage. I’ve noticed far fewer bug each ensuing year on my potatoes. We also rotate planting spots and do a good job scouting to make sure we keep up with the beetles.

  9. Charlene grootenboer says:

    I have been ambushed by the CPB, Japanese beetles and squash bugs! Between the weather, weeds and bugs I gave thought to going out with the rototiller and mowing everything under! Where a lot of these larvae live in the soil if you set fire and burned all the grass/weeds/vegetation would it also burn up and kill the insects?

  10. Gordon Haymon says:

    For the last few years I have noticed Colorado beetles on my young potato plants and picked off a few. But then I noticed a flatish bug lying on the leaves and no CBugs in numbers. I think I identified this as an ambush beetle and that it helped to keep the CBugs under control I use no pesticides at all and so am not disrupting the native insects or bugs at all. This might be a worth while thing to check into, the ambush beetles, I mean. Best to you, Gordy, NY

  11. Tamara says:

    No BT Tenebrionis is not available anywhere. I get pretty sick of people recommending it all the time without having used it. I live in an area with thousands of acres of potato fields. When they kill the plants this time of year the bugs are especially bad. In some years I can squish thousands per day. Spinosad works but only spray potatoes and other non-bee plants. It will harm bees when fresh.
    I have used the plastic lined ditch. My spuds were especially bad that year but I think it was the area. After a few weeks I had a sewer and realized you have to poke holes in the plastic. However, what scares me about exclusion of the potatoes is they will go to the eggplant; so you isolate those too; then they go to the tomatoes; then trench those; then they eat peppers, etc. So I cannot physically dig a trench around all the nightshade crops in my half acre so I guess I would rather they concentrate on the potatoes.

  12. Nate says:

    From what I have read regular BT is not effective at killing Potato Beetle Larva. Only Bacillus thuringiensis var. tenebrionis BTT is what has been developed, but I have found no commercial availability of this strain. Anyone else know more about this???

    I grow 2+ acres and the hand picking method has been great. I hire young family members to go and hand pick… they actually have a blast filling up Gatorade bottles full of the adults. Bennifical releases of lady bugs seemed to hit the larva pretty hard. Planting strips of Barley in between and on the edges of potato crops attracts huge numbers of beneficial insects.

    I also rotate crops between fields located at least 2 miles apart and this has helped considerably. This year I planted 3 miles apart and have found 1, yes one single adult, where last year we picked off over a thousand of the suckers!!! Whatever you do don’t plant where you have lots of Night Shade weeds as Potato beetle is sure to be near by.

  13. Margi says:

    I have planted sweet potatoes with my potatoes and had no CPB’s last year and few this year. (Lost a few sweet potatoes this year and only have beetles where I have a big skip in the planting.) A man in the grocery store related this method to me last year. Anybody else experimented with this?

  14. Judy Weymouth says:

    We live in Buxton, Maine. Due to frequent rain this season (terrible haying weather!), I hand-picked CPB from two 50′ rows every other day. Organically-approved controls (sprays, dust) are pretty expensive, especially if you apply them 5AM & they’re washed off by 5PM. Finally had a break in the weather (dry forecast for next 3 days, wow) & applied Spinosad spray after handpicking. Now, nearly 2 wks later, I’m beginning to see a few larvae & adults again. Not too worried, as Red Norland vines are dead, & others will follow soon.

  15. Mike McGrath says:

    Based on research some years back we developed a method that seems to work well here in Delaware. We prepare a good bed with tillage and place the cut seed potatoes directly ON THE SURFACE of the bed. Then we cover the beds with 12″ of loose straw, covering the entire width of the bed – about 36″. The trick is to maintain the covering of straw throughout the growing season, renewing it at least weekly to maintain a full 12″ thickness (we made us a “measuring stick” so workers could be sure) across the entire width. Make sure the straw stays loose, not applied in “mats” as is sometimes done in straw mulching. Our results have been – almost zero CPB!! While this method may be too labor-intensive for large acreage, we have found it eminently doable for several hundred hills of Irish potatoes. The bonus? Harvest is so easy!! Rake off the straw and, voila, potatoes very near the soil surface and easily harvested. May work for you.

  16. Bob Spencer says:

    In the past few days, I may have discovered a spray mix that kills the potato beetle and Japanese beetles. I mixed canola oil and dish detergent with water in my sprayer. I just walk down the rows and zap them. It kills them quickly.

    Apparently, they do not return to the spots where I spray.

    I am curious what experiences others have with this mixture. I also sprayed my apple trees as a substitute for Neem oil for aphids and mites. We’ll see what happens with that.

    Bob Spencer

    • J Cameron says:

      Can you please advise how you mix/ what portions you use for this potato beetle spray.. and what type (make) of dish detergent is used.. a more specific recipe to help us with a huge infestation that is destroying our potato crop would be very welcome!!

      Thank you.

      • High Mowing Organic Seeds says:

        Here is a recipe for a homemade potato beetle spray. I have not tried it personally, but apparently they despise horseradish. You could also try a spray of 10 cloves of garlic, a few tablespoons of horseradish, and a pint of water pureed and strained into a spray bottle. This is an adequate deterrent for many garden pests, and doesn’t harm the plant. I usually use Safer Insecticidal Soap, which is formulated to not harm plants or people and dissolves insects’ waxy coatings, killing them in minutes. Dish detergents can harm plants, so if you’re going to use one, test out your recipe on just a small area before spraying the whole crop. Here is a page that gives advice on diluting soap for pesticides.

        Spearmint Hot Pepper Horseradish Spray: Effective on many different kinds of outside bugs and insects and should be an outside spray.

        ¼ cup of hot red peppers

        ½ gallon water

        ¼ cup of fresh spearmint

        ¼ cup horseradish, both root and leaves

        1 tablespoon of liquid detergent

        ¼ cup green onion tops

        Mix the spearmint leaves, horseradish, onion tops and peppers together with enough water to cover everything. Then strain the solution. Add ½ gallon water and the detergent. You can use this to spray almost any plant safely. Store the mixture for a few days in a cool place.

        • douglas says:

          Order one of my traps and see how amazingly it works against cucumber beetles. I had terrible problems in my garden until I we put out the first trap in my garden. For the six years I have lived on this property I was never able to grow melons on my property because of those pesky critters and then last year I was able to grow cantaloupes with zero leaf damage.

  17. E says:

    Where I live, south eastern Ontario, potato crops planted in late June are vigorous bountiful and virtually CPB free. I use this method for our potatoes. I don’t feel that early crops are worth it.

    For eggplant we hand pick the CPB off of our 400 plants.

  18. Pingback: The Unique Challenge of Colorado Potato Beetles | High Mowing Organic Seeds Blog | Grow So Easy Organic

  19. RCGauer says:

    Thanks… did not know they were land-bound after emerging! PS: Come back to the New Mexico Organic Conference this year!

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