Glasshouse and field experiments on the control of tobacco blue mould

Abstract

A simple procedure is described for the testing of chemicals against blue mould (Peronospora tabacina Adam) on tobacco seedlings in the glasshouse. Of approximate/y 500 chemicals tested, 17 gave mould control comparable to that of the standard (0.1 per cent w/v zineb), but a number of these were phytotoxic. In two field trials, zineb and ethylenethiuram monosulphide as dispersible powders or suspensions in white spraying oil base and N-p-tolyl dichloromaleimide as a dispersible powder, gave highly effective control early in the season, but later in the season, only zineb at 0.1 and 0.2per cent w/v gave effective control. Maneb, which was not tested in the field, later proved consistently superior to zineb in extensive glasshouse trials, and appeared to be the most promising compound for further investigation.