Impact
The primary aphid species found on potatoes in the San Luis Valley are the green peach aphid, Myzus persicae, and the potato aphid, Macrosiphum euphorbiae.

Aphids transmit virus diseases, notably Potato Virus Y (PVY) and Potato Leafroll Virus (PLRV). The green peach aphid is the most efficient vector of PLRV to potato; potato aphid is less efficient but may be important in some locations and seasons. Many other aphid species transmit PVY. Significant direct injury from aphid feeding rarely occurs, except during extreme outbreaks. The San Luis Valley has a comprehensive aphid suppression and monitoring program,run here at Agro Engineering, to control green peach aphid populations which occur annually. Populations vary in intensity depending on environmental conditions.

Description and Symptoms

Wingless green peach aphids tend to be pear shaped. They may have variable colors but usually are straw-colored or light-green. Hind cornicles slant so they converge. A key characteristic is tubercles at the base of the antennae.

Potato aphids are more elongate and larger, about 1/6 to 1/8 inch, than the green peach aphid. They often are bright green, but pinkish forms occur. They are similar in general appearance to the English grain aphid.

Both potato and green peach aphids produce winged forms. Winged aphids are most important in spread of viruses to plants since they move readily within and between fields.

Wingless green peach aphids tend to occur on lower, older potato leaves. Potato aphids more commonly colonize the upper part of the potato plant.

During the summer, aphids reproduce asexually (no males) and give live birth to young. Under optimal conditions, a generation may be completed in 10 days.

Several predators and parasites help control aphids. Among the more important insects are lady beetles, damsel bugs, green lacewings, minute pirate, and parasitic wasps.

Green peach aphids overwinter in the egg stage on various Prunus species, particularly plum and apricot, in and around towns. It may also be introduced on infested greenhouse plants. Potato aphid overwinters in the San Luis Valley on wild rose.

Integrated Management

Monitor flights of winged aphids by using yellow traps and follow the weekly San Luis Valley monitoring reports.

Apply pesticides only when necessary. Use of some insecticides can exacerbate aphid problems, because the control has more effect on natural enemies than on aphids. Insecticides can only provide limited control of aphid transmitted virus diseases. The green peach aphid can be highly resistant to insecticides registered on potatoes. Therefore, choose insecticides carefully for effective control.

Protect natural predator populations that are important in aphid management.

This material is based on work supported by the San Luis Valley Water Quality Demonstration Project Best Management Practices Advisory Committee, Colorado State University Cooperative Extension, Farm Service Agency, Natural Resources Conservation Service, and the U.S. Department of Agriculture under authorization as 1991 U.S. Department of Agriculture Water Quality Demonstration Project.