Plant Disease in an Old Field Ecosystem Irrigated with Municipal Waste Water

Abstract
During 1978 and 1979, plant disease on foliage was assessed in an old field dominated by goldenrod (Solidago canadensis and S. graminifolia) and quackgrass (Agropyron repens) and irrigated with waste water. Plant pathogens abundant in waste‐water‐irrigated areas included, Coleosporium asterum, Erysiphe cichoracearum, Phyllachora graminis, and Helminthosporium sp.; such fungi reportedly alternate their life cycles or reproduce on economically important plant species. The increased foliar disease in the irrigated areas was probably due to increased moisture. Frequencies of plant pathogens in the waste water were apparently low since wounded seedlings of numerous crop varieties immersed in waste water remained healthy. Alternaria alternata and Stemphylium sarcinaeforme survived equally well after 24 days in filter‐sterilized waste water or tapwater; however, Erwinia herbicola and E. atroseptica survived longer than 24 hours in buffered waste water but not in buffered tapwater.