Caren White is a Master Gardener and instructor at Home Gardeners School. She has been associated with Rutgers Gardens for over a decade.
What are Potato Beetles?
The Colorado Potato Beetle (Leptinotarsa decemlineata) originated in Colorado where it munched happily on native buffalo burs, a relative of the potato. Then European settlers arrived in 1859 with potatoes and the beetles switched to this more abundant crop. They munched their way back east, following the potato "trail" moving up to 85 miles per year until they arrived on the East Coast in 1874.
The adults overwinter in the soil. In the spring, they emerge and start eating your potatoes' foliage. Then they mate and lay eggs on the leaves. A female potato beetle lays 10 to 30 eggs at a time, up to 350 in her short lifetime. The eggs hatch within two weeks. The resulting larvae are more voracious than the adults.
Once the larvae have eaten their fill, they dive down into the soil to pupate into adults. Pupation lasts 10 to 15 days which means that more than one generation is possible each summer. In the South with its longer growing season, three generations are possible. In the North, one to two generations is typical. If it is late in the season when the larvae pupate, they will overwinter in your garden, emerging in the spring to begin the cycle again.
Till Your Garden and Rotate Your Crops
You can break the cycle in the fall with a deep cultivation of your soil which will kill the larvae.
Crop rotation is another good way to disrupt the life cycle of the beetles and the larvae. By not planting potatoes in the same spot next year, the beetles and larvae will emerge in the spring and find nothing to eat.
A good rule of thumb is not plant potatoes in the same spot for two years. If you divide your garden into quadrants with each quadrant containing a different family of vegetables, you can rotate your quadrants. And example of this would be to have one quadrant for solanaceous plants, one quadrant for legumes, one quadrant for cucurbits and a fourth quadrant for vegetables from other families such as onions and lettuce. That way it will be four years before you plant potatoes in the same part of your garden again,
Surround Your Potatoes With a Trench
Barrier methods are always a good way to prevent potato beetles from getting to your potatoes. Dig a trench around your potatoes and line it with plastic creating a bare area and fooling the beetles into thinking that there is nothing planted in the vicinity. Beetles are not too bright.
Use Floating Row Covers
Another good barrier method is floating row covers. They are "floating" because you just lay them loosely over your plants. The thin polyester material allows light and rain to get in but keeps insects out provided you anchor the sides using pins, rocks or bury them in soil. Since potatoes do not require pollination, you don't have to worry about preventing pollinating insects from getting to your plants. In the spring, row covers also keep in heat, warming the air and soil and encouraging your plants to grow faster. You can leave the row covers over your potatoes until you are ready to harvest.
Hand Pick Potato Beetles Off of Your Plants
If you aren't squeamish, you can manually pick off the adults and larvae from your plants and kill them by either squishing them or dropping them into a container of soapy water.
Don't forget to check the undersides of the leaves for the yellow eggs. They can also be picked off and destroyed thereby preventing an entire generation of beetles.
Invite a Few Enemies to Your Garden
Use salt hay as a mulch in your garden and you will be accomplishing two things. First, mulch makes it more difficult for the beetles to find your plants. Secondly, you will be attracting beneficial insects such as predatory wasps and lady bugs which like to nest in the hay and eat potato beetles. Add a birdbath and insect eating birds will drop by for a quick dip and a snack of beetles.
Establish a small pond or wetlands near your garden and toads will take up residence. They will visit your garden and eat their fill of potato beetles and other insects. If you don't want to dig a pond in your yard, you can leave an overturned flower pot and a dish of water in your garden. Toads are nocturnal. They spend the day hiding in shady sheltered spots. Since toads absorb water through their skin, the water dish should be deep enough for them to completely submerge themselves.
Colorado potato beetles are a scourge that we brought on ourselves by introducing potatoes into their environment. You can keep their numbers down using a variety of organic methods.
© 2014 Caren White
Caren White (author) on July 07, 2014:
Flourish, I'm glad you enjoyed it. Thanks so much for the pin!
FlourishAnyway from USA on July 07, 2014:
I haven't heard about these pests but enjoyed reading about them. Voted up and pinning to my Garden & Outdoors board.
Caren White (author) on July 07, 2014:
Thanks Eddy! I got involved with the new vegetable garden where I volunteer and I'm learning all about insects and disease.
Eiddwen from Wales on July 07, 2014:
Interesting and very useful.Voting up and sharing.