One of the most dangerous pests of potatoes is the Colorado potato beetle. The beetles were first noticed on potatoes in 1859 when they switched from their usual host plant, buffalo bur. They first began to infest potatoes in Colorado but gradually began to migrate east to other states. Both the adults and their larvae feed on the leaves of the plants and can completely defoliate them. Few synthetic insecticides are effective as controls against the beetles.
Potato beetles are oval winged insects with hard bodies that measure 3/8 inch long. They are orangish with yellow wing covers that bear 10 black stripes. The bright orange eggs may appear under the leaves of the potato plants and hatch within two weeks. Larvae start out red with black heads and mature to a salmon color. The also have two rows of black spots along their sides. A female beetle can lay 350 eggs in her brief lifetime.
Controlling Potato Beetle
Potato beetles are almost completely resistant to synthetic insecticides after years of building an acclimation to the chemicals. The best route of control is a combination of methods. Planting early maturing varieties may help escape some of the insect's damage. Handpicking and biological controls such as stink bugs and lady beetles may be useful in smaller gardens. Chemically, carbaryl and permethrin were the common formulas to control the beetles but they have largely developed a resistance. The only synthetic insecticide that is still effective alone is esfenvalerate, which has a persistence of up to four weeks.
Ambush is an insecticide that contains permethrin. The chemical is an active ingredient in creams formulated to combat scabies, a skin disease caused by minute mites. The product needs to be applied if there is one larva per plant or one adult per plant. Ambush is applied at a rate of 3.2 to 12.8 oz. per acre in 14-day rotations as long as the potatoes are actively growing. This is because the orange eggs can continue to hatch over several weeks and any living potato beetle adults will continue to lay eggs.
Butacide is a synergist. When it is used in combination with a common pesticide it can increase its effectiveness and help overcome resistance. Butacide is the trade name for a compound with the active ingredient piperonyl butoxide. Butacide, or its ingredients, is effective as a synergist to block resistance to insecticides. The product is used at a rate of 0.5 to 1 pint per acre. Piperonyl butoxide comes in other trade names such as Incite and Prentox PBO-8.
Combination Use as Resistance Management
The use of piperonyl butoxide combined with permethrin is a common lice treatment and is an extremely effective duo for overcoming insect resistance to previously applied chemicals. Resistance management relies upon rotation of chemicals used to prevent a buildup of resistance. Preferably the rotation is among different classes of insecticides to prevent resistance to the same mode of action. Ambush is a pyrethroid and should not be used in alternation with other pyrethroids. If it is the only chemical that is as available it will perform best with the addition of the Butacide.