EFFECT OF FIVE INSECTICIDES ON POPULATIONS OF THE SIX-SPOTTED LEAFHOPPER AND THE INCIDENCE OF ASTER YELLOWS IN CARROTS

Abstract

Five insecticides were evaluated for their ability to control the aster leafhopper, Macrosteles fascifrons (Stål), and to reduce the incidence of aster yellows disease, transmitted by this vector in carrots. Furadan (2,3-dihydro-2,2-dimethyl-7-benzofuranyl methylcarbamate) as a single granular treatment at seeding was as effective in reducing the level of aster yellows disease as five or eight foliar treatments with carbaryl (1-naphthyl N-methylcarbamate) in 1967 and 1968. Oxydemeton-methyl (O,O-dimethyl S-[2-(ethylsulfinyl)-ethyl]phosphorothioate) was comparable with carbaryl in reducing aster leafhopper numbers and incidence of aster yellows disease. Disulfoton (O,O-diethyl S-[2-(ethylthio)ethyl]phosphorodithioate) as a single granular application at seeding was the least effective treatment in this study. Aster yellows incidence in carrots treated with DDT [1,1,1-trichloro-2,2-bis(p-chlorophenyl) ethane] was only slightly lower than with carbaryl in a commercial scale trial. A 5-day insecticide spray schedule was not appreciably more effective than a 10-day schedule.