The potato beetle is well known for its ability to develop resistance to many insecticides making it one of the most difficult garden pests to control.
Description: Colorado potato beetles (Leptinotarsa decemlineata) are such a common pest in home gardens that they are often just called “potato bugs.” Both the adult and larval forms chew leaves and can completely defoliate an entire crop if potato beetle control methods are not implemented. Their feeding can greatly reduce yield and in some cases, may even kill plants. Alternate host plants include tomatoes, peppers and eggplant.
Adults (1/3 inch long) are rounded, yellowish-orange beetles with black stripes on their wings and black spots just behind the head. The plump larvae (1/8 to 1/2 inch long) are red with black head and legs, and become yellowish-red or orange with two rows of black spots on each side of the body.
Life Cycle: Overwintering beetles hibernate in the soil or garden debris, emerging in the spring. At this point, they do not have enough energy to fly and must walk in search of suitable host plants. Females lay orange-yellow eggs in clusters on the undersides of leaves. In 4-15 days (depending on temperature) hatching occurs, and the voracious larvae begin feeding on foliage for up to one month. When mature, they drop from the plant, enter the soil and pupate, emerging as adults 5-10 days later. There are 1 to 3 generations each year.
Colorado Potato Beetle Control: Plant resistant cultivars when possible. In early morning, shake adults beetles from plants onto ground cloth and dump captured pests into soapy water. To impede the movement of overwintering adults, mulch at least 2-3 inches deep with a layer of clean straw or hay as soon as plants emerge. Protect plants with floating row covers through spring. Beneficial insects, such as ladybugs, spined soldier bugs and lacewing, feed on eggs and the young larval stages. Beneficial nematodes will attack the immature stages in the soil. Monterey Garden Insect Spray (Spinosad) is a highly effective biological insecticide recommended for use against potato beetles. For best results, apply when young. Spot treat with botanical insecticides if pest levels become intolerable. After harvest pick up garden debris and turn the soil over around plants to disturb overwintering beetles.
Tip: Line trenches between potato rows with plastic to trap adults. A recent study found that trenches with walls sloping at greater than 46 degrees will retain an average of 84% of all adults caught.