Investigations on Forest Trees Resistance to Armillaria spp. : Root and Butt Rots

Uppsala

International Union of Forest Research Organizations, Swedish University of Agricultural Sciences

1994

S. 17-25

10 Lit. Ang.

Bandaufführung

73424

Investigations were carried out to evaluate the susceptibility to Armillaria of different conifer and broad leaf species under natural and/or artificial infections. Under natural infection only Armillaria ostoyae was detected. It was found that more frequently Pinus cembra, followed by Pinus sylvestris, Abies alba, Picea abies, Pinus uncinata, Juniperus communis and Larix decidua were involved. Hardwood species were infected only rarely. On Quercus, particularly on Quercus cerris, but also Quercus pubescens, Quercus robur, and Quercus ilex, root rots caused by Armillaria tabescens, Armillaria gallica and especially Armillaria mellea were found only on trees declining from drought or stagnant water. These fungi rarely attacked trees in good vegetative condition. Artificial inoculations were carried out with Armillaria mellea, Armillaria gallica and Armillaria tabescens (10g of inoculum per plant) on two-year-old seedling of Quercus cerris, Quercus ilex, Quercus petreae, Quercus pubescens, Quercus robur and Quercus rubra grown in a greenhouse. A group of inoculated seedlings was exposed to a water regime close to the soil field capacity; another to a water regime close to the wilting point. The group exposed to water shortage was the only one damaged. Quercus cerris was confirmed to be the more susceptible species, Quercus rubra the less one. Armillaria mellea was the most aggressive species, followed by Armillaria gallica and Armillaria tabescens. Other artificial inoculations were carried out in the field with the three Armillaria species on three-year-old seedlings of the above mentioned species of Quercus and on two-year-old plant of different Populus species. All young trees showed consistently good vigor. No infections were detected 1 year after inoculation.