The disease caused by the root-rotting fungus is probably one of the most insidious threats to the long-term health of UK forests. OMEX is a leading supplier to national commissions and land agencies for the supply of Dyed Urea, which is commonly used to treat stumps in hundreds of hectares of UK forest.
Conifer root and butt rot
The disease caused by the root-rotting fungus Heterobasidion annosum is probably one of the most insidious threats to the long-term health of UK forests and can cause significant loss of revenue through it's ability to kill or cause decay in standing trees.
In the 1950's the most important elements of the biology of the disease were unravelled by Dr John Rishbeth of Cambridge University. He investigated serious outbreaks of the disease in first-rotation pine plantations in East Anglia where large numbers of trees were killed by the fungus soon after thinning began. Dr Rishbeth demonstrated that freshly-cut stumps are infected by airborne spores and that the fungus subsequently infects surrounding trees through root contacts.
In new plantations which are free of the disease, infection only developed after thinning. Clarification of the essential role of thinning stumps in the disease cycle provided a basis control whereby freshly-cut stump surfaces are treated with urea solution to prevent spore infection.
Spores that settle on freshly cut stumps may germinate and begin the process of colonization, leading to the infection of adjacent healthy living trees within a few years through root contact between the stump roots and the living trees. Evidence suggests that a stump may remain susceptible to infection for several weeks after the tree has been felled and it is now clear that stumps of all conifer commonly grown in the UK are susceptible, especially those of pine.
In many Forestry Commission forests, it has been policy since 1960 to treat stumps immediately after felling, based on Rishbeth's work demonstrating both the cause of infection and a possible cure.
OMEX Dyed Urea
On most sites the only substance approved for use against butt rot is urea solution. It's mode of action is not fully understood but, on decomposition, it releases ammonia gas which is toxic to spores of Heterobasidion. It also supplies a source of nitrogen in the stump which stimulates the growth of antagonistic fungi. In part, it's role would therefore seem to be a subtle enhancement of biological control by naturally occurring non-pathogenic fungi.