Comparison of Three Products Based on Phlebiopsis gigantea for the Control of Heterobasidion annosum in Europe

Abstract

The fungus Phlebiopsis gigantea has been used in Europe as a biological agent for the control of conifer root and butt (caused by Heterobasidion annosum ) for nearly 40 years. P. gigantea competes with H. annosum for the woody resource within conifer stumps, and is applied to stump surfaces at felling. Three distinct biological control products based on P. gigantea have been developed: PG Suspension in the UK, PG IBL in Poland and Rotstop in Finland. The formulations are of oidia, which are maintained in a sucrose suspension, sawdust, or a wettable powder, respectively. PG Suspension and PG IBL are applied to pine stumps, while Rotstop is equally as effective on pine as on Norway spruce stumps. For each product, isolates of P. gigantea are selected from the wild and are screened for their competitive ability against H. annosum before formulation. Viability and purity checks are undertaken throughout the production cycle and during routine use. The increasing use of mechanized harvesting machines to fell and process trees is having an impact on this biological control system, the formulations having to be compatible with the mechanical application systems and vice versa. This paper compares the formulation, testing and application of the three products, and considers some aspects of their future development.