Foliar Sprays to Control the Colorado Potato Beetle on Irish Potatoes, 1978

‘Norchip’ Irish potatoes were planted, 10-inch spacing in 3-ft rows on Mar 31 ‘78. Treatment plots were replicated 4 times in a randomized block design. Each plot consisted of a single, 25-ft-long row bordered on each side by an. untreated row. The sprays were applied with a D. B. Smith 5-gallon, knapsakc, hand-operated, compressed-air sprayer at the rate of 100 gal/acre (40 psi) using a D. B. Smith #E-147 adjustable cone nozzle. Applica-tions were made on Jun 1, 12, 19, 26, and 30. In evaluating the various insecticidal treatments, direct counts of the number of potato beetle larvae/10 hills and late season foliage injury ratings were utilized. The several categories for the foliage injury ratings are as follows: 1) Only occasional chewing, necessary to look very close to see evidence of feeding damage; 2) Visible signs of feeding but less than 10% of the leaves severely injured; 3) Severe feeding on 25% of foliage; 4) Heavy feeding on 50% of foliage; 5) Practically 100% of foliage severely damaged, plants nearly defoliated; and Def - Plants completely defoliated. Yields were taken on July 26.