Impact
The potato psyllid overwinters in the southern region of North America. Infestations that develop in the San Luis Valley originate each year from winged migrants moving in from overwintering areas along the border of the United States and Mexico.

Economically significant outbreaks of potato psyllid are uncommon in the San Luis Valley and are dependent on large migrations that occur approximately once every five years.

Description and Symptoms

The adult psyllid resembles a tiny cicada and is about 1/8 inch long.

The nymphs are flattened, scalelike and pale yellow-green.

Damage is caused by nymphs that inject a toxin while feeding. The toxin induces a condition known as psyllid yellows. Feeding by adult psyllids has little or no effect on potato yields at any time.

As few as three or four psyllid nymphs per plant can produce psyllid yellows on pre-bloom plants under favorable conditions.

Immature leaves on infested plants turn red or purple and are abnormally erect, with the basal portion cupped.

Older leaves become unusually thick, roll upward and turn yellow. Internodes become shortened.

Affected plants produce aerial tubers and excessive numbers of small,distorted tubers, which may sprout without a dormant period. Skin set and sugars are also affected in tubers from infested plants.

Yield effects occur when plants become infested early in the season

Integrated Management

Scout for psyllids before initiating control measures.

Increase scouting for nymphs seven to 10 days after finding adult populations. Nymphs are most frequently found on plants exhibiting psyllid yellows.

Scouting for nymphs should concentrate on the lower leaves of early planted potatoes. Examine 50 leaflets randomly selected throughout the field. Potato psyllid can be difficult to scout on potato plants, since popula- tionstend to occur in patches on lower, shaded leaves. Within fields, adult psyllids, but not immature nymphs, are best sampled with a sweep net.

Apply insecticides whenever nymphs can be easily detected in fields. Treat if more than two to four adults are captured per 100 sweeps and nymphs are detected in fields.

Protect natural enemy populations by avoiding use of insecticides that adversely affect psyllid predators. Some insecticides (Sevin, Furadan) may aggravate psyllid problems because of effects on their predators.

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.