EXPERIMENTS ON CONTROL OF THE SIX-SPOTTED LEAFHOPPER, MACROSTELES FASCIFRONS, AND ASTER YELLOWS ON HEAD LETTUCE WITH CONTACT AND SYSTEMIC INSECTICIDES FN MANITOBA

Abstract

Thimet®, Di-Syston®, Bayer 39007 (o-Isopropoxyphenyl methylcarbamate), American Cyanamid (AC) 43,064 (2-(diethoxyphosphinothioylimino)-1,3-dithiolane), AC 47,470 (2-(diethoxyphosphinylimino-4-methyl-1,3-dithiolane), and AC 47,031 (2-(diethoxyphosphinylimino)-1,3-dithiolane), in granular formulations (G), and malathion, Delnav®, Thiodan®, and Bayer 39007, in emulsifiable concentrate formulations (EC), were tested in field plots for control of the six-spotted leaf hopper, Macrosteles fascifrons (Stål), and protection of head lettuce from aster yellows virus (AYV) in spring and summer crops in Manitoba in 1962 and 1963.In 1962, malathion, Thimet, and Bayer 39007 G significantly reduced the numbers of leafhoppers in both the spring and the summer crop. In 1963, the same chemicals with Bayer 39007 in both G and EC formulations significantly reduced the numbers of leafhoppers and partly protected the lettuce from AYV in the spring crops but not in the summer crop. The other insecticides tested were ineffective. The failure of all treatments to protect the summer crop against AYV was apparently due to a combination of a large population of leafhoppers with a high percentage of viruliferous leafhoppers.