Cladobotryum spp. are responsible for cobweb disease of mushrooms. In two commercial and one experi-
mental mushroom-growing room, Cladobotryum conidia were released into the air in direct response to physical
disturbance of disease colonies during either crop watering or treatment by covering with salt to 10 mm.
Conidia were detected using a Burkard spore trap or agar-based trap plates. A maximum concentration of
25,000 conidia m3
was recorded in a small (75-m3
salting of 16 cobweb patches (0.55 m2
). Concentrations of 100 and 40 conidia m3
) experimental growing room in the hour following the
were recorded in the two
larger commercial growing rooms in the hour following the salting of 18 and 11 patches of cobweb (diameter,
approximately 50 to 200 mm), respectively. In controlled experiments, disturbed conidia were dispersed rapidly
throughout a small growing room, with 91 to 97% of conidia settling out within 15 min. Eighty-five percent of
conidia settled out within a 0.5-m radius when air-conditioning fans were switched off, consistent with airborne
spore dispersal. Alternative methods for treating diseased areas to minimize conidial release and distribution
were investigated and included covering disease colonies with damp paper tissue prior to salt application
(tissue salting) and holding a dust extractor above disease colonies during salt application. Both methods
resulted in no detectable airborne conidia, but the tissue paper salting technique was more convenient.
Prevention of airborne conidial release and distribution is essential to avoid mushroom spotting symptoms,
secondary colonies, and early crop termination.