Factors affecting uredospore liberation in Puccinia antirrhini

Abstract

Air sampling within an annular field plot of rusted snapdragons, and in a wind tunnel, has shown that uredospores of Puccinia antirrhini are readily liberated by wind shear at speeds = 2 m/sec. At constant temperature and wind speed, most uredospores are liberated in the light, mainly in the morning. Liberation in dry air is related logarithmically to wind speed; it is increased by the onset of rainfall or overhead sprinkling, and by bombarding sori with water droplets in the wind tunnel.