Environmental effects on survival and growth of secondary sporidia and teliospores of Tilletia indica.

Abstract Several aspects of the growth, survival and control of propagules of Tilletia indica were studied. The germinability of secondary sporidia of T. indica on glass slides at 25°C was assessed after incubation in air of 25%, 50%, 70%, 85% and 95% relative humidity. Sporidial survival declined most rapidly at the lower relative humidities, but at any r.h. did not exceed 14 h. On potato dextrose agar, germ-tube elongation rates were 0·33, 0·42, 1·86, 4·04, 5·40, 0·94 and 0·0 μm/h at 5°, 10°, 15°, 20°, 25°, 30° and 35°C, respectively. The survival of teliospores in the field was assessed in soil at two locations. Germinability of seeded teliospores increased at both locations slightly after 7 months; however, after 22 months only the germinability of teliospores buried in dry soil remained high. The efficacy of methyl bromide, vapam and formalin treatment to reduce teliospore germinability was assessed at the surface and at depth of 5 cm and 10 cm in wet and dry soil. Methyl bromide reduced teliospore germinability more than 98% at all depths in wet soil. In dry soil, none of the fumigants were very effective.