CONTROL OF THE SIX-SPOTTED LEAFHOPPER, MACROSTELES FASCIFRONS, AND ASTER YELLOWS ON HEAD LETTUCE IN MANITOBA

Abstract

Malathion, Sevin® (1-naphthyl N-methylcarbamate) and Bayer 39007 (o-Isopropoxyphenyl methylcarbamate) were tested in the field for the control of the six-spotted leafhopper, Macrosteles fascifrons (Stål), and protection of lettuce from aster yellows in Manitoba in 1960 and 1961. Malathion at 1 pound per acre at 3-day intervals and at 2 pounds per acre at 4-day intervals controlled the leafhopper and protected the lettuce from aster yellows. At 2 pounds per acre at 6-day intervals malathion was less effective against the leafhopper but still provided adequate protection against aster yellows. Sevin at 1 and 2 pounds per acre at 6-day intervals and Bayer 39007 at 1 pound per acre at 3- and 6-day intervals were as effective as malathion at 1 pound at 3-day intervals. Severe infestations of aphids developed after the use of Sevin; Bayer 39007 left an objectionable white deposit on the lettuce. In early spring crops, treatments that were started 4 weeks after crop emergence were as effective as those started at crop emergence. In summer crops, treatments started 2 weeks after crop emergence were as effective as those started at crop emergence. Nine days after the last of 15 applications of malathion there was a residue of less than 0.5 p.p.m. on the lettuce.