Every year during the third cucumber crop cycle, there is a possibility that diseases in the substrate can increase. Pythium, botrytis, mosaic virus and fusarium can be increasing without anyone noticing. Before planting, it can be very helpful to replace infested slabs. Some growers do this by laying a fresh slab beside or below the gutter next to an infected slab during the last weeks of the old crop. Do this with a dense slab with closed planting holes. That way you start off with much less risk of infection.
Source: RijkZwaan Growing Partner