The resin in the wood is organic as well as the wooden fibres and
the damp that is in it. The organic compounds supply the algae nutrition
and helps the algae spoors establish themselves quicker.
A pure wooden surface –or a painted one- is often organic. Onto the surface, dirt gets stuck, which binds moisture –which gives the affections more nutrition.
Spores that have gotten a hold grow quick. The affection on an organic material develops faster than on an inorganic. To stop affection and growth, all the surfaces pores requires to be totally sanitized from spores and algae. Both on the surface as well as in the pores.