For many growers the lack of quality mushrooms in the third flush is reason enough to stop after the second flush. This is understandable if there is a high risk of disease present, but in a low risk situation it’s often a shame not to use this opportunity to get the maximum from the expensive compost.
Increased susceptibility to bacterial blotch and faster discoloration in the third flush are often problems that occur as the mycelium in the casing soil ages. Water is occasionally given after the second flush and even on the third which only makes matters worse regarding discolouration. In this situation try not to sprinkle after the second flush and work with minimum circulation and ventilation. The poor conditions will restrict the number of pinheads which is beneficial here.
During the third flush mushrooms take most of their water from the compost. Excess water in the casing soil doesn’t have to be evaporated then. Only sprinkle after the second flush if the casing soil still appears fresh and the mycelium is vigorous.
John Peeters, C point