THE USE OF TETRACHLORONITROBENZENE ISOMERS ON POTATOES

In laboratory and field experiments from 1952 to 1955, 2:3:5:6-tetrachloro-I-nitrobenzene (tecnazene) delayed the development of sprouts on treated potato tubers, and 2:3:4:6-TCNB retarded sprout development in two laboratory experiments. At the usual commercial rates of application the 2:3:4:5 isomer had no effect on sprout development and very little effect at higher rates. The crop from 2:3:5:6-TCNB-treated seed tubers usually contained a higher proportion of small tubers than that from untreated or 2:3:4:5-TCNB-treated seed. Marketable yield from 2:3:5:6-TCNB-treated seed was sometimes below that from untreated seed, but when this happened the yield from 2:3:4:5-TCNB-treated seed was higher.
Both isomers produced good control of dry rot, Fusarium caeruleum (Lib.) Sacc., on five varieties of potatoes, but did not produce a commercial control on Doon Star. To achieve control, the isomers had to be present at the time of infection. There was some evidence that the development of disease symptoms was delayed in treated, infected tubers. Since 2:3:4:5-tetrachloro-1-nitrobenzene has no sprout depressant action it merits further trial as a fungicidal treatment for seed potatoes.