The Colorado potato beetle (CPB) is a challenging pest that has plagued farmers for decades. It is one of the most serious and damaging potato pests. If left uncontrolled, farmers suffer yield losses caused by CPB feeding on leaves that can completely defoliate plants.
Follow these tips for scouting and managing CPB in your potatoes.
The CPB is easy to spot, they are somewhat rounded and have 10 narrow black stripes running lengthwise over a yellow-cream background wing cover.
Females lay clusters of bright yellowish-orange oval eggs on the underside of leaves. The eggs are yellow and often found in masses of 20-40 eggs. Closer to hatching, the eggs will turn dark orange. Each adult female is capable of laying up to 400 eggs during their lifespan of four to five weeks.
Weather conditions determine the number of CPB generations per season. In Ontario, CPB generally completes two generations during the growing season, with a third generation developing if the summer is warm. In the fall, adult beetles burrow into the soil either in potato fields or in protected places surrounding the fields to overwinter at depths of 25–35 cm.
Occasionally in New Brunswick, Nova Scotia and Prince Edward Island, some of the new adults emerge early enough to mate and lay some eggs, creating a partial second generation. However, these mated adults soon stop producing eggs and start preparing for overwintering. The partial second generation usually develops too late in the season to have a significant impact on potato yield in these provinces.1
Evidence of CPB can be first noticed along the outside edges of potato fields. If spring weather is warm, beetle emergence may be very rapid. During cooler springs, CPB emergence may be slower.
Depending on the weather, CPB larvae typically begin to appear in July. When scouting, look for CPB feeding on top of plants, especially if the weather is warm and sunny. On cooler days, the pest will hide under soil or foliage, so be sure to scout diligently.
Mating and egg laying occur shortly after CPB emergence. Depending on temperature, eggs hatch into larvae within four to nine days. Once hatched, CPB larvae are orange-red and humpbacked, with two rows of black spots on each side of the body. There are four larval stages (instars) of the CPB. Old larvae (the last or fourth larval instar) are responsible for as much as 75% of feeding damage.
Farmers can rely on insecticides for control, but CPB can develop resistance, creating additional challenges when it comes to managing the pest.
For more information about scouting and CPB thresholds, visit the Ontario Ministry of Agriculture, Food and Rural Affairs' Colorado potato beetle crop information page.
A combination of pest management tactics can reduce CPB numbers, including:
Delegate™ insecticide with Jemvelva™ active is the best choice for rapid knockdown and long-lasting control of CPB and is an excellent rotational product for use in an Integrated Pest Management system.
Delegate is formulated with Jemvelva™ active (spinetoram), a naturally-derived product that is fast-acting against a wide range of insect pests including CPB, with minimal impact on beneficials and the environment. As the active ingredient in Delegate, spinetoram provides a unique mode of action, providing farmers with an important resistance management tool.
CPB larvae are easiest to control when they are young. Farmers should target application timing when larvae start to appear, typically in July.
With an easy-to-use formulation, Delegate offers low use rates delivered through a convenient dry formulation. Correct coverage and water volume are key to a successful Delegate application. Organic matter can bind to the insecticide’s active ingredient, so farmers should be sure the water being mixed in the tank is clean and the pH should be 5-9. Another benefit of Delegate is that it can also be applied during higher temperatures.
For more information about controlling CPB, contact a Corteva Agriscience horticulture expert.
