Factors influencing the growth ofPithomyces chartarumin pasture

Abstract

Abstract An examination of factors which could influence the growth of Pithomyces chartarum and the development of facial eczema toxicity in pasture indicated that: 1. 1. Growth and sporulation on dead grass leaves and stems is most rapid under warm (70°F to 80°F) moist conditions. It is retarded by prolonged exposure to high levels of moisture around the dead herbage, and considerably accelerated on tissues with a high content of soluble organic material, e.g., freshly dead, well-nourished leaves.2. 2. The ability of spores to adhere to live leaves is directly related to the wettability of the leaf surfaces.3. 3. The wettability of the lower epidermis of ryegrass leaves is high. The upper epidermis of ryegrass leaves and both surfaces of the leaves of paspalum and cocksfoot are difficult to wet. The lower epidermis of white clover leaves is moderately wettable.4. 4. Spore germination is greatly stimulated by cell exudates from damaged areas on live leaves of ryegrass or paspalum provided the leaves are moist. Dilute juice pressed out from ryegrass leaves has a similar effect on spore germination.5. 5. As judged by nitrogen analyses, considerable quantities of soluble organic material are readily available at the surface of immature leaves of ryegrass if they are wetted after being grown under warm moist conditions. This is not the case with mature leaves.6. 6. Germination of spores followed immediately by a period of rapid mycelial growth in dilute ryegrass juice can lead to a significant rise in facial eczema toxicity within 15 hours.