Environment and sporulation in phytopathogenic fungi. III. Peronospora tabacina Adam: Field environment, sporulation, and forecasting

Abstract

An account is given of measurements of temperature and humidity at a number of positions and heights within a tobacco crop during a 4 day period. Measurements of the intensity of sporulation of Peronospora tabacina Adam were made at the same time. It is shown that the capacity of P. tabacina to sporulate is controlled not only by nocturnal humidity but also by day temperature. The observations confirm that Cruickshank's laboratory findings hold in the field. The implications of the observations reported here, together with those of other workers on such factors as the spore dissemination and germination characteristics of P. tabacina, are discussed. It is concluded that the basic information necessary to initiate, on a trial basis, a blue mould forecasting and spray warning service is now available.