EXPERIMENTS ON THE EFFECT OF CHLORINATED NITROBENZENES ON THE SPROUTING OF POTATO TUBERS

The addition of a small quantity of a dust containing pentachloronitrobenzene to clamps of certain early and second-early potato varieties has a marked effect in reducing the amount of sprouting which takes place over winter and in protecting the sprouts from damage by the fungus Rhizoctonia Solani.
A series of yield trials carried out over six seasons has shown that tubers which have been stored in clamps in presence of the dust give yields equal to those of chitted tubers.
A dust containing a tetrachloronitrobenzene applied to potatoes kept in a closed space represses sprouting to a very pronounced degree. The possible use of this dust for conserving ware potatoes is suggested.     

EXPERIMENTS ON THE MOVEMENT OF STREPTOMYCIN IN CHERRY TREES

Systemic activity of streptomycin in cherry trees was investigated by studying the penetration of the antibiotic into leaves and its subsequent translocation.
Antibiotic penetration appreciably suppressed infection with Pseudomonas morsprunorum. In detached leaves the uptake of the antibiotic was progressive with time.
Widespread and rapid distribution of the antibiotic in the transpiration stream resulted from petiolar injection. Immersion of the laminae of intact leaves in the antibiotic resulted in a much slower translocation, possibly occurring in the transpiration stream.
Evidence suggests that the antibacterial activity detected in fruiting spurs after field spraying is not dependent on the presence of leaves, but results from direct penetration of the antibiotic through the dermal tissues of the spur.
It was concluded that foliar sprays at field concentrations were unlikely to result in significant systemic distribution of the antibiotic, but that localized activity might be an important factor in the control of bacterial canker.     

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.