APHID INFESTATIONS ON KATAHDIN AND ON A SEEDLING RESISTANT TO MYZUS PERSICAE (SULZ.), WITH TWO DATES OF PLANTING

Abstract

In August under field conditions, on early planted plots, the number of Myzus persicae per plant was usually over five times as great on Katahdin as on B294-85; and the number of Aphis abbreviata was over 10 times as great on Katahdin as on B294-85. The differences in the aphid populations on the late planted plots of Katahdin and of B294-85 were similar, but not so great. There were no consistent differences in the numbers of Macrosiphum solanifolii on Katahdin and on B294-85. During August, the rates of increase of each species were similar for both varieties and dates of planting. The number of aphids per plant was many times greater on the early planted than on the late planted plots, the differences being greater between the Katahdin than between the B294-85 plantings. When the populations were expressed as aphids per unit leaf area, the distribution of each species on the top, middle, and bottom leaves was similar in all cases.