Design and use of an automatic humidity chamber in phytopathological research

Inexpensive humidity chambers, equipped with spore traps, were designed for the study of various ecological phenomena. The basic apparatus enables cycling conditions of any desired humidity with a period of high humidity with or without leaf wetness; and two conditions of air movement through the chamber, each of them chosen in the range of 0 to 14 1/min. The chamber’s performance was tested withUromyces phaseoli on beans in relation to (a) the duration of leaf wetness needed for infection, (b) the effect of relative humidity on the appearance of sori. and (c) the amount of sori and the number of uredospores produced. Iiberated and trapped under various conditions of relative humidity.