The idea of a vegetable garden pest that reproduces rapidly, overwinters in the soil, and whose larvae can decimate plants sounds like a nightmare for any gardener. However, that is a fairly accurate description of the Colorado potato beetle.
Anyone who grows potatoes at home should be familiar with Colorado potato beetles. These conspicuous pests are everywhere and they gorge themselves on crops. They don’t just go for potatoes, as Colorado potato beetles can also be attracted to other crops from the nightshade family.
I have been growing potatoes in the UK for many years, both professionally for chefs and in my own vegetable patch. Although I have not personally experienced Colorado potato beetles, the pests continue to spread worldwide. All potato growers should know the distinguishing features of the pests, the signs to look out for and learn how to control Colorado potato beetles.
Colorado beetles have striking stripes on their backs
(Image credit: Getty/Mixmike)
Where can you find the Colorado potato beetle?
The Colorado potato beetle gets its name from the place where the pest was first discovered. Today, however, these pesky beetles can be found in gardens and farms everywhere. The insects are believed to be found in most U.S. states and are found throughout Central America, Europe, and parts of Asia.
What are Colorado potato beetles?
The larvae of the Colorado potato beetle have an enormous appetite
Colorado potato beetles can be a real problem when growing potatoes. They are about a half inch long and are recognizable by the orange-yellow and black stripes on their wings. The adults have a hard shell and are oval, while the larvae have a soft shell, a red body and a black head. The larvae also have two rows of dark spots on each side of their body.
The beetles lay their eggs on the underside of leaves in clusters of 20-40. The eggs of the Colorado potato beetle are bright yellow-orange in color, oval in shape and are attached to the leaf at the end.
The life cycle of a Colorado potato beetle is rapid. Female Colorado potato beetles can quickly lay over 500 eggs. These eggs hatch in less than a week, and the beetle can go from egg to adult in about three weeks. The speed of the Colorado potato beetle life cycle means that up to three generations of pests can hatch each growing season.
Michelle Brugh, founder of Forks in the Dirt and co-author of Small-scale self-sufficiencydescribes them as “a persistent pest” because they spend the winter underground. They overwinter 4-12 inches deep in the soil of areas they fed on the previous season.
‘The following summer they emerge and feed for a few weeks before laying eggs on potato leaves,’ Michelle adds. ‘These hatch as heavy-feeding, brick-red, black-headed larvae. The larvae and striped orange and black adult beetles can really decimate potato crops.’
Colorado potato beetles can destroy more than just potatoes. They also feed on other plants in the Solanaceae family, including eggplant, tomatillo, tomatoes and peppers, and can quickly damage crops.
Michelle Bruhn
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Master Gardener
Michelle Bruhn is the founder of Forks in the Dirt and co-author by Small-scale self-sufficiency, available on Amazon. She is a nature-loving Master Gardener and advocate for locally grown food on the outskirts of the Twin Cities, MN.
The signs of damage by the Colorado potato beetle
Colorado potato beetles can quickly decimate potato plants
(Image credit: Getty Images/BasieB)
Susan Mulvihill, author of The Handbook on Pests in the Vegetable Garden And The Handbook for Solving the Vegetable Garden Problemsays that ‘both the adult insects and the larvae cause much damage to the host plants by chewing’.
The damage caused by the larvae is the most serious and can amount to three quarters of the damage. That is why it is so useful to combat the young beetles.
“The larvae chew on the leaves of the plants and leave behind dark frass,” Susan says. Frass is the excrement that the larvae leave behind and it will be visible on the plant and is a sign of the presence of larvae.
Regular inspection is essential to spot and control potato pests. The other thing to look for are the yellow or orange tubular Colorado potato beetle eggs on the underside of the leaves of the host plants.
The plants can tolerate some defoliation, up to 20 percent, but more damage can affect the potato yield. They are more susceptible to defoliation when the tubers are swelling, which begins after the potato plants have started to flower.
Susan Mulvihill
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Vegetable expert
Tips for combating the Colorado potato beetle
Look for Colorado beetle eggs on the underside of the leaves
Close inspection of plants every few days is essential to detect damage immediately and take prompt action. Begin checking potato plants, as well as other host plants, in the spring when Colorado potato beetles emerge.
“Hand picking is a great way to control them and crush any eggs you find,” says Susan Mulvihill. Adult and larval beetles can be picked off the plants and thrown into a container of soapy water.
Adults can fly in from other gardens once temperatures reach 70°F. This means that crop rotation in a home garden may not completely control pests, but the practice is still recommended to prevent soil-borne pests and diseases.
Susan answers one way to protect a crop: ‘It is possible to cover potato plants with floating row covers throughout the growing season because the flowers do not require pollination.’
A good biological control for the Colorado potato beetle is to incorporate companion plants into your vegetable garden. Adding flowers to a vegetable garden can deter many pests and attract predators of the Colorado potato beetle.
“Marigolds (French or Lemon Yellow) and nasturtiums can help deter these beetles,” says Michelle Bruhn.
‘You can also attract ladybugs, which eat the eggs, by planting flat flowers such as dill, yarrow and marigold.’
Susan Mulvihill advises that there are organic sprays that are effective against the Colorado potato beetle, including kaolin clay, Neem oil, plant extracts and spinosad. She cautions, however, “Be aware that Neem and spinosad are toxic to pollinators, so don’t spray near flowers.”
Treatments are best timed when the larvae are small. Due to the continuous use of chemicals over many decades, Colorado potato beetles have developed resistance to many insecticide products.
Buy flower seeds for combined cultivation
Hundreds of small flowers cover neat, low mounds of lacy foliage with a citrusy scent that can deter pests in a vegetable garden.
‘Sparky Mixture’ is a well-known alternative to the traditional marigold. The plant quickly grows to 30 to 35 centimetres in height and has unique, semi-double heads.
A packet of heirloom dill seed from ‘Bouquet’ which produces 90cm tall plants with strongly scented leaves, stems and flat flower heads.
Frequently Asked Questions
What is the natural enemy of the Colorado potato beetle?
Ladybugs, stink bugs, ground beetles, lacewings, spiders, mites, and parasitic wasps are all predators of the Colorado potato beetle. They are all thought to attack the eggs and young larvae of the pest, while birds, frogs, and toads eat the beetle, larvae, and eggs. Companion plants with flowers to attract insects, adding plants for birds, and attracting frogs with water sources are all ways to attract predators as part of natural pest control.
As mentioned, Colorado potato beetles can also cause problems if you grow tomatoes – they’re one of many pests that can affect tomato growers. To learn more and discover ways to combat them organically, read our dedicated article on tomato pests , complete with expert tips for dealing with outbreaks.
