Changes in extractives of Scots pine (Pinus silvestris L.) after ISPM 15 heat treatment and their effect on fungal discolouration

According to the International Standard of Phytosanitary Measures (ISPM No. 15), heat treatment is currently the most important method to be used on wood-packaging material to avoid the spread of harmful quarantine organisms such as insects and nematodes. During a pure phytosanitary heat-treatment operation (without any kind of drying) pine sapwood in particular shows an increased affinity towards mould and blue stain. In the present study chemical changes in the wood were detectable after heat treatment. These changes promote fungal metabolism and, in consequence, the increasing affinity of heat-treated wood. The content of elutable lipid components and the content of free sugars increased, whereas the pH value of the wood decreased. Further investigations led to environmentally compliant agents which temporarily inhibit fungal germination on the surfaces of the wood. The fungistatic effect is mainly based on the reduction in the content of fats and the change in the pH value of the wooden surface.