Vol. 43

Title:
Fungus and Relative Humidity

Author:
Bent Løchenkohl

pp: 189

Abstract:
The environment in propagation units is ideal for fungi to grow—nice warm temperature and high relative humidity (RH). At the same time it is difficult to use fungicides in a propagation unit. Therefore, cuttings have to be free of fungal diseases by good care of the stockplants. Under normal conditions in a greenhouse, should there exist a high RH, climate computers are able to control it—this is not the case in a propagation unit.

Fungi grow small hyphae, 4–6 µm in diameter, that develop into mycelium. In order to grow, fungi have to absorb water so that nutrients can move into the hyphae. If transpiration is too high, the hyphae dry out and the Therefore, from the fungi's point of view it is not the RH but transpiration and subsequent condensation which controls its growth.

It takes some time to get used to considering evaporation instead of RH as controlling the growth of fungi. Even in a greenhouse with 100% RH, evaporation\transpiration occurs because some areas are warmer and others

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