Experimental use of a native isolate of Phlebiopsis gigantea: efficacy and eco-sustainability.

Heterobasidion annosum is an important pathogen, causing conifer root and butt rot. In Italy it attacks Pinus species both in mountain and in coastal plantations. Its diffusion is greatly enhanced during thinning, as its aerial inoculum germinates on new wounds or freshly cut butts. During thinning in the Castel Fusano Pinus pinea forest (Rome, Italy), in 2002-2005, a biological control trial was carried out for preventing new disease centres of a North American population of H. annosum, whose airborne spores were abundantly present. In particular, in February 2003 a suspension prepared with a native isolate of Phlebiopsis gigantea, previously studied in controlled environment, was applied on 23 butts. Observations on efficacy and persistence of the isolate in the treated stumps were carried out thirty months later. The pathogen was never detected in the stumps treated. Moreover, it was impossible to re-isolate from the upper part of the butts the P. gigantea individual isolate which had been profusely applied. These results confirm that the used isolate is an efficient biological control agent on P. pinea against the exotic isolates of H. annosum, and it is safe from an ecological point of view, as it does not trouble the natural succession of micro-organisms in butts