Factors Affecting Biological Control of Spurred Anoda (Anoda cristata) withAlternaria macrospora

In greenhouse studies, spurred anoda [ Anoda cristata (L.) Schlecht.] control by Alternaria macrospora Zimm. was influenced by stage of growth, inoculum concentration, and the temperature and duration of the dew periods following inoculation. Seedlings inoculated at the cotyledon to first-leaf stage were most easily controlled. Optimum dew periods for killing seedlings were ≥ 24 h at 20 to 30 C. Spray mixtures containing 2.5 to 10 × 10 5 spores/ml gave the best control. In field studies, A. macrospora significantly reduced the number and the dry weight of spurred anoda plants.