Nymph Spring Migrant
(Shown 10X actual size)
Ornamental plum, apricot, peach, and cherry trees are pretty, but they are a problem in the San Luis Valley because they serve as the only over-wintering site of one of the potato industry's most serious pests, the Green Peach Aphid. This insect is known to carry several viral diseases of potatoes, including the Potato Leaf Roll Virus. The ornamental trees that harbor the GPA can be found in landscape and back yard locations throughout the Valley.
The Green Peach Aphid lays its eggs on the trees in the fall. They hatch in early spring and feed on plant juices from peach, plum, apricot and cherry trees. Winged forms of the aphid move to vegetable and flower gardens and potato fields during the summer. When an aphid feeds on a plant that has leafroll virus, it becomes a carrier and can cause other potato plants that it feeds upon to become infected. In this way the virus can spread rapidly through a field. For seed potato growers, the virus is a severe problem because fields that show the presence of infected plants may not pass the state certification program, a program which ensures growers both in and out of the state that disease-free seed is available. Seed that is certified can command a better price than non-certified seed. In the San Luis Valley, seed potato production is a major industry and expands each year as the reputation for quality grows.
The most effective way to control the Green Peach Aphid is by removing plum, apricot, peach, and cherry trees because the GPA cannot survive the winter without these host trees. To control the aphid on trees that bear fruit or are in good health, a dormant oil solution is applied to the trees in the spring before the leaves appear. Dormant oil kills the aphid eggs that have been laid on the trees by suffocating them. This does not harm the tree, and can benefit the tree by helping to reduce the populations of other harmful insects. To ensure effectiveness, in some cases a mild insecticide is added to the oil. After the trees break dormancy and bud out, dormant oil can no longer be used, and use of an insecticide is necessary. If you spray your own trees, be sure to contact your county extension agent before mixing or applying any pesticides.
Each year since 1975, the San Luis Valley Potato Administrative Committee, with cooperation from Colorado State University, has funded a program to reduce the Green Peach Aphid population in the Valley in an effort to make the area free of Potato Leafroll Virus. As the majority of plum and apricot trees are grown by homeowners, their cooperation is vital in making the program effective. Since the trees can hurt the Valley's potato farmers, local nursery stock dealers are asked to refrain from selling these ornamental fruit trees in the San Luis Valley.
The program is paid for by the San Luis Valley Potato Administrative Committee. For no charge to homeowners in the Monte Vista, Del Norte, and Center areas, The program will either remove unwanted plum, apricot, peach, or cherry trees or apply a dormant oil solution to reduce the number of aphid eggs. The oil application will be done by licensed personnel, and all safety precautions will be observed. The Suppression Program has historically shown great success in reducing the population of the Green Peach Aphid and the occurrence of Potato Leafroll Virus.
By controlling the number of aphid eggs that hatch each season, potato growers can reduce insecticide applications and also get better prices for clean seed. The cooperation of the Valley's homeowners is greatly needed for the success of the program.
