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. Upon emergence, potato beetles travel on foot for several days and sometimes over a mile to seek out a food source and reproductive location. 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. 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. 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. The most common broad spectrum OMRI-approved organic pesticide is called Entrust, in which the active ingredient is spinosad. 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. 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.
Hello Tamara, I know this is years old, but the original product was called Novodor and it was available from Valent. The label is still online, but the product has been discontinued.
Certis makes a product called Trident, that is Bacillus thuringiensis var. tenebrionis. It is also OMRI listed. It is not packaged for home users, so you would need to buy a 2.5 gallon jug. That would be enough for about 1.5-3 acres. Which is actually a really small amount for a 2.5 gallon jug. Normally a 2.5 gallon jug is formulated for 40-80 acres.
This product would most likely be available from a local agricultural chemical co-op that sells to farmers who grow vegetables.
Maybe this would be a possible product that High Mowing could offer repackaged in smaller quantities such as a quart or gallon? In any event, it IS available.
The other problem with spinosad is that it does NOT work on adults. Once the beetles have a hard shell, the only other option is hand picking or Pyganic. Pyganic is not normally effective in killing adults. It was so over used, along with many of the synthetic pyrethroids (which have the same mode of action), that most Colorado potato beetles are resistant to every very strong doses.
While I try to do everything organically, I can't let acres of potatoes be defoliated to the point I lose a crop. My spray rotation is as follows:
No Adults-Only Larvae: Spinosad. Usually to replications to kill newly emerged larvae and then the remaining flush
Adults: Evergreen (Pyganic plus Piperonyl butoxide), followed by two applications of Spinosad.
Evergreen was once OMRI listed and was then delisted when they determined the PBO component was too refined and was deemed a synthetic. I am sorry, but this product is very safe for people. If applied in the evening when pollinators are not present, then the risk to them is very low. When working in an organic system, we also need to keep in mind that overuse of crop protectants without proper rotation will lead to the loss of control of those pests.
There is going to be a blurring of the organic and man-made products in the future. Bio-Controls are becoming a big part of the non-organic segment of agriculture.
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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.
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.
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.
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.
For eggplant we hand pick the CPB off of our 400 plants.