Symptoms and Signs
Vines infected with Armillaria root rot usually completely collapse. Occasionally, white mycelial mats can be found under the bark at the soil line, but more commonly white mycelial strands are seen interwoven through darkened cortical tissue. Dark, rootlike structures called rhizomorphs grow from the root into the soil after symptoms develop on vines.
Comments on the Disease
The fungal pathogen survives on diseased wood and roots below ground for many years. Healthy plant roots can become infected when they come in contact with inoculum from a preceding orchard crop, nearby oak trees, or remnants of Armillaria-infected roots when land is cleared and prepared for planting kiwi vines. Although kiwifruit plants are somewhat tolerant of this fungus, if the vine has already been weakened by Phytophthora infection, its death may be hastened by an invasion of A. mellea. Flood waters sometimes spread infected roots in a vineyard. The fungus is favored by soil that is continually damp. Although the pathogen may produce mushrooms around the base of the vine trunk, they are not considered significant in disease spread.
When clearing land for planting or replanting vines, carefully remove and burn roots 1 inch or greater in diameter. Ensure that vines are properly irrigated and not overwatered.