Green peach, melon or potato aphid may occur in potato, colonizing fields from mid June through July. Potato aphid is the largest of the three.
Potato aphids are 3-4 mm long, and may be pink or green. Cornicles are the same color as the body with dark tips.
Plants of the rose family serve as alternate hosts to potato aphid in fall and spring. A wide range of weeds, field crops and vegetable crops are hosts in summer. In potato they feed first in young growing tips, spreading downward into older leaves. Injury includes leaf deformity and dieback.
Aphids spread viruses to seed and tablestock potatoes, which can reduce yields and quality. High populations of aphids can cause foliage to decline.
Monitoring & Thresholds:
Fields should be scouted for aphids starting in late June. Examine aphids/leaf on 50 fully grown compound leaves (5 leaves at ten locations in the field) from top, middle and bottom of the canopy. In fresh market and processing potato, the thresholds for insecticide application is when an average of five aphids per leaf are present, or 10 per leaf within two weeks of vine kill. In Maine, the economic threshold for tablestock and processing fields is when aphids are found on 50 percent of the plants or one winged aphid is found within the field.
Cultural Controls & Prevention:
Plant disease-free certified seed to avoid introducing viruses which could be spread by aphids.
Chemical Controls & Pesticides:
Use selective or systemic insecticides for Colorado potato beetle control in order to conserve natural enemies of aphids, which are abundant.
For current information on methods (including varieties, spacing, seeding, and fertility), weed, disease, and insect management, please visit the New England Vegetable Management Guide website.