Bacterial blotch regularly occurs in the months between September and December mainly following a spell of warm humid days. The cause of bacterial blotch is always an evaporation problem. Evaporation problems can occur at various times
The bacterial blotch seen currently mainly occurs in a later flush. The problem has then often been caused by sprinkling to maintain moisture levels after the first or second flush. It is important that casing soil no longer glistens with moisture a day after sprinkling. Not glistening means the reflection of the lamps in the growing room can no longer be seen in the casing soil. In the winter and during dry spring days this usually happens automatically. Sprinkling causes the room RH to rise. Then increase ventilation to remove excess moisture and allow the room to dry. In humid weather this process takes longer so the beds also stay wetter longer
How can you prevent casing soil remaining wet for too long?
Firstly try to give water in the shortest space of time possible. Make sure the water is absorbed by the casing soil.
Secondly use the drying schedule. In the drying schedule various settings can be changed for a certain time For example:
Give Fresh air 5% higher.
Lower RH 5% lower
Temperature 1 degree higher
Change these settings for a 3-hour period. This will dry the casing soil surface quicker and reduce the risk of bacterial blotch.