THE USE OF TETRACHLORONITROBENZENE ISOMERS ON LETTUCE

Field experiments were carried out from 1951 to 1955 on winter lettuce plants grown in boxes under glass and in the open, and on commercial crops in unheated glasshouses. Each of the three isomers of tetrachloronitrobenzene, applied as 5% dusts at 1/4 and 1/2 oz. per square yard of bed, gave significant protection against Botrytis disease, but the 2:3:4:5 isomer was inferior to the other two isomers and they all delayed the hearting of the crop. The 2:3:4:5 isomer at both rates of application and the 2:3:5:6 and 2:3:4:6 isomers at 1/2 oz./sq.yd. delayed hearting of a commercial crop by more than 14 days and are not recommended at these rates. Local overdoses of fungicide should be avoided.