Insect Predators for Controlling Aphids on Potatoes. 3. In Small Plots Separated by Aluminum Flashing Strip-Coated with a Chemical Barrier and in Small Fields1

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Abstract
In 1966, 8-in, aluminum flashing standing on edge proved effective as a barrier to interplot movement of the larvae of Coccinella septempunctata L. when introduced sequentially into 0.014-acre plots of potatoes; notwithstanding, the small plots proved unsatisfactory for evaluating effectiveness of the introduced predators, chiefly because of the habits of the predators. The flashing had a 1-1½-in, band at the top on each side coated with Fluoro Glide®, technical grade. Approximately square ¼-acre fields were superior to 12x50 ft plots for evaluating effectiveness of manual introductions of 2nd and 3rd instars of C. septempunctata or 2nd instars of Chrysopa spp. against aphids on potatoes. In small fields having light-to-moderate aphid infestations, better control was obtained from sequential introductions of Chrysopa spp. at 88,100 larvae/acre than from 4 applications of C. septempunctata at 30,500 larvae/acre. However, the best all-season control was achieved where introductions of both predators at these rates were made in the same field. Best all-season control ranged from 33 to 97%, depending upon species of aphid; for all species of aphids combined, it was 58. The abundance of predaceous stages of coccinellids and chrysopids during the summer on sample aphid count leaves in the fields or plots was not well correlated with the numbers of C. septempunctata or Chrysopa spp. introduced into the plantings.

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