Reduction of Lettuce Yellows with Systemic Insecticides1

Abstract

Ten systemic insecticides and 1 nonsystemic insecticide were investigated for prevention of the lettuce yellows virus disease through control of the vector, the aster leafhopper, Macrosteles fascifrons (Stal). Of these phorate, Baygon® ( o -isopropoxyphenyl methylcarbamate) and NIA 10242 (2,3-dihydro-2,2-dimethyl-7-benzfuranyl methylcarbamate), applied in the furrow at planting time, were the most effective in reducing aster yellows. These 3 materials controlled the vector up to 11 weeks after their application. Delaying their application until the time of thinning was too late for most effective control. Applying ½ the dosage at planting and the other ½ at thinning time was no more effective than applying the full dosage at planting. Weekly sprays with carbaryl, Baygon, or oxydemetonmethyl were effective in reducing lettuce yellows, but not to the same extent as the granular systemic treatments. Insecticide 1179 (methyl N -[(methylcarbamoyl)-oxy]thioacetimidate) applied as a spray to the soil in a 2-inch band following planting reduced the incidence of early infection, but foliar applications which followed were not so effective as the soil treatment.