The centenary oak trees in Doñana National Park are considered vital structures in transition ecosystems between scrublands and wetlands in the area. These trees are threatened nowadays by the presence of a pathogen oomycete (Phytophthora cinnamomi) which is included among the 100 worst alien invasive species in the world. This invasive species has spread around the world, being a threat to 900 woody plant species. It was first detected in meadows in Spain in 1992.

This pathogen causes the mass mortality of absorbing roots, leading to symptoms similar to those associated to drought. The pathogen lives on the ground in the form of very resistant spores, which germinate when there is free water in the soil and the temperature is relatively high. Zoospores can swim and are chemically attracted by the extreme oozing of cork and holm oaks. In Doñana Nature Area, P. cinnamonmi was first isolated in 2008 and later samplings suggest that the pathogen has now widely spread.

The control of P. cinnamomi is complicated due to the spores' long-life. In Australia, a place where the pathogen is threatening numerous native species, several methods have been tried to eradicate it. These have included drastic treatments such as the destruction of healthy trees in areas bordering the disease sourcing areas through the irrigation with fungicides or the use of injections with chemical fumigants. Experts in Doñana have recommended the treatment with resistance inductors using injections in the trunk to boost the tree's response to the pathogen.

The Life ADAPTAMED project will treat 200 cork trees in Doñana Nature Area with phosphonate injections. Monitoring will be implemented before and after the treatment to check the efficiency of the measures taken including the examination of 300 cork trees. The results obtained will feed into a "guide to oak treatments".

More information: Guyonne Janss

Photo: Cork oaks in Doñana Nature Area. ©Héctor Garrido / EBD-CSIC