ON FUNGAL DAMAGE TO SUN‐EXPOSED COTTON DUCK

Abstract

OBSERVATIONS ON the kinds of fungi found on cotton fibers and cotton cloth are numerous. In many instances, the investigators have been primarily concerned with fungi of the more superficial types growing on the sizing and other non-cellulosic carbon compounds of the fabric. The reports, however, of the fungi responsible for the decomposition of fabric such as awnings and tentage under actual conditions of outdoor exposure when not in contact with the soil, are much more limited (Broughton-Alcock, 1919; Thaysen and Bunker, 1927) and have not been quantitatively evaluated. Techniques employed for isolating organisms supposed to be primarily responsible for the actual decomposition of cellulose in cotton fabric have frequently erred on two major counts. Those methods employing nutrient agars with sugars as a source of carbon favor the rapid growth of any fungus or bacterium suited to that substratum, whether or not it be a cellulose decomposer. The method using filter paper and mineral salts agar while isolating some cellulose decomposers fails to detect many others because it does not take into account the fact that cotton fibers in gray duck supply vitamins B1, B6, and biotin (Robbins and Ma, 1942), as well as other possible nutritional constituents for fungi having special requirements (Robbins and Schmitt, 1945). Gray duck in contrast to bleached duck retains the protoplasmic contents left in the lumina of the natural fibers, as well as fragments of seedcoats, leaves, and the like. Bleaching and scouring largely remove these remnants. The natural cotton fiber, on a moisture-free basis, contains the following percentages of elements expressed as means of several readings (Beeson, 1941): 0.59 per cent K, 0.13 per cent Ca, 0.09 per cent Mg, 0.054 per cent P, 0.05 per cent S. Raw cotton on a moisture-free basis is reported (Marsh and Wood, 1942) to contain 0.2 per cent N, and bleached cotton none. Of the data available on the minor elements, iron and manganese are both present on a moisture-free basis in raw cotton as 190 parts per million. It is presumed, however, that other minor elements are present.