Don’t Allow Potato Beetles to Bug Your Vegetable Garden
Article written by Jessica Strickland, Extension Agent-Horticulture
Q: How can I control Colorado potato beetles on my potatoes?
A: If you have ever grown potatoes in your vegetable garden you have probably experienced a problem with Colorado potato beetles. These beetles, sometimes referred to as potato bugs, are a common pest problem that can quickly feed on potato leaves in the spring. Routine monitoring for potato beetles now can help you catch and manage them before the populations get out of hand.
To regularly monitor for Colorado potato beetles, the first important step is to be able to recognize the insect at different stages of its life cycle. Being able to identify the beetles in the egg stage can make control quicker and more effective than waiting until you see adult beetles. The female beetles lay eggs in masses on the underside of the potato leaves in May. The mass of eggs will be bright orange and football shaped. The eggs hatch in four to nine days. A single female adult beetle can lay up to 500 eggs in a month. As the eggs emerge, you then have the immature form of a potato beetle known as the larvae. The larvae causes the most damage because they continuously feed for two to three weeks before finally turning into adults. The larvae are about ½” long and have dull red, humpbacked bodies with black legs and two rows of black dots running down their sides.
Once the larvae are full size, they drop to the ground and pupate in the soil, emerging as adults five to ten days later, and thus the cycle begins all over again with the adults laying more eggs. The adults are similar in size to ladybugs, except they are slightly narrower, dull yellow, and have black stripes along their wings. Colorado potato beetles can have two to three generations each year, and are usually found actively feeding on plants from May through July. They prefer potatoes but can be found feeding on vegetables that are close relatives to potatoes, including tomatoes, peppers, and eggplant.
The first defense in controlling potato beetles is regular monitoring for egg masses on the underside of leaves along with looking for larvae and adults on the tops of leaves. Plants should be inspected every couple of days and hand pick any eggs, larvae and adults from the plant. Adults and larvae can be dropped into a bucket of soapy water, while the eggs should be squished.
Controlling potato beetles with an insecticide can be difficult because some have developed resistance to commonly used insecticides such as carbaryl (Sevin). An organic insecticide that has been found to be very effective in controlling the immature (larvae) beetles is spinosad (sold as Captain Jack’s Dead Bug Brew, Greenlight Lawn and Garden Spray with Spinosad, and other brand names). For this product to be effective, it should be applied as soon as beetle eggs or larvae are found. Like other organic insecticides, spinosad does break down quickly and would need to be reapplied often to provide protection. When handling any pesticide, whether organic or synthetic, carefully read and apply according the label directions.
Another important control measure for potato beetles is to practice crop rotation. Crop rotation refers to the practice of not growing the same type of vegetable plant in the same place year after year. Potato beetles are an insect that survives in the soil over winter and if you plant potatoes in the same location each year, this will allow for the insect population to build up creating more of a problem each year. Keep a record of where you plant vegetables in your garden and do not plant the same vegetable or one of its close relatives in that spot for at least two years. Close relatives to avoid planting where potatoes where include tomatoes, peppers, and eggplants.
For more information on managing Colorado potato beetles or other garden and lawn questions contact the Wayne County Extension Master Gardener Volunteer Plant Clinic on Mondays and Wednesdays from 10 a.m. to 1 p.m. The plant clinic is a free resource to Wayne County residents. One can reach the Wayne County Extension Master Gardener Volunteer Plant Clinic by phone at 919-731-1433, e-mail at Master.Gardener@waynegov.com, or stopping by Room 100 of the Wayne County Extension Office (208 West Chestnut Street, Goldsboro). People contacting the plant clinic can also pick up soil testing kits, get assistance in reading a soil test report, and bring (or e-mail pictures) weeds, plants, or pests for identification.
Recommendations for the use of agricultural chemicals are included in this article as a convenience to the reader. The use of brand names and any mention or listing of commercial products or services in this article does not imply endorsement by North Carolina Cooperative Extension nor discrimination against similar products or services not mentioned. Individuals who use agricultural chemicals are responsible for ensuring that the intended use complies with current regulations and conforms to the product label. Be sure to obtain current information about usage regulations and examine a current product label before applying any chemical.
Upcoming Wayne County Extension Gardening Programs:
• The Wayne County Extension Master Gardener Volunteers will be holding a Leaf Casting Workshop on Saturday, July 26th from 9 a.m. to noon at the Wayne Regional Agricultural Fairgrounds. This workshop will allow you to create one medium size leaf casting using cement, sand and water. Workshop registration fee is $25. Pre-payment and registration is required by Friday, July 18th. Space is limited to 25 participants, so early registration is encouraged. For more information and to get a registration form, contact Wayne County Cooperative Extension at 919-731-1520.
• Visit our website at https://wayne.ces.ncsu.edu/. Click on “Lawn & Garden” on left side of webpage.
• “Like” us on Facebook to receive timely garden tips, ask questions, and learn of upcoming gardening events. www.facebook.com/waynecountygardening
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North Carolina Cooperative Extension
Wayne County Center
P. O. Box 68
Goldsboro, NC 27533