The susceptibility of forest trees to Armillaria root rot

The susceptibility of forest trees to Armillaria butt and root rot is described. The paper characterises the most common Armillaria species and presents the mechanical, physiological and chemical mechanisms of plant resistance against Armillaria. The importance of stress as a cause of increased susceptibility of plants to infection is emphasised. Stress in plants may be caused by drought or an excess of water in the soil, inappropriate temperature, unsuitable soil pH, shortage of oxygen in the ground, wrong nutrition, lack of light, pollution of the soil or air, and the presence of damaging macro−, mezo− or microflora and fauna. Stress decreases the production of cambium in the affected area, the production of resins that limit colonisation, the intensity of photosynthesis, respiration and the transport of nutrients. Stress causes the hydrolysis of carbohydrates necessary for production of energy required for resistance responses, increases accumulation of glucose and other substances used by Armillaria, favours the degradation of phenols that limit colonization, increases susceptibility to other stress factors, and decreases regeneration of the trees