Insect Predators for Controlling Aphids on Potatoes. 2. In Small Plots with Two Kinds of Barriers, in Small Fields, or in Large Cages1

Abstract

Interplot movement of introduced and naturally occurring predators of aphids on potatoes in small plots prevented accurate assessment of the effects of sequential introductions of eggs and larvae of Coccinella septempunctata L. or Chrysopa spp. Neither barriers of oats nor 8-in. aluminum flashing standing on edge on the soil’s surface prevented interplot movement. Interplot movement of predators appeared to be a less confusing factor in small fields than in small plots. Larger sized plantings will be required to assess the effects of introduced predators unless a successful harrier can be devised to confine the predators in smaller plots. Results in large field cages corroborated those in small fields and showed when 2 species of aphids were present on potato plants, larvae of C. septempunctata are more potato aphids. Macrosiphum euphorbiae (Thomas), than green peach aphids, Myzus persicae (Sulzer) whereas larvae of Chrysopa spp. consumed more green peach aphids than potato aphids.