Mushroom Brown Blotch: Effects of Chlorinated Water on Disease Intensity and Bacterial Populations in Casing Soil and on Pilei

Abstract

Severity and incidence of brown blotch caused by P. tolaasii (= P. fluorescens) in the cultivated mushroom (A. bisporus) was reduced by routine waterings with chlorinated water. Both disease severity and incidence were closely correlated with the occurrence of P. tolaasii on mushroom pilei, but not with numbers of P. tolaasii in the casing soil. Bacterial populations in the casing soil were not correlated with those on the surface of mushroom pilei. Thus, control of brown blotch apparently is due to protection of pilei rather than reduction of bacterial popualtions in casing soil. The efficacy of chlorinated water was not significantly increased by acidification (pH 3.5) with HCl.