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

Abstract

The fungus Phlebiopsi s 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 eVective 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 throughou t 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 biologica l control system, the formulations having to be compatible with the mechanical applicatio n systems and vice versa. This paper compares the formulation, testing and applicatio n of the three products, and considers some aspects of their future development.

Wood production, wood technology, and biotechnological impacts

“…A cost range comparable to chemical treatments, uncomplicated manual or mechanical application and the ease of formulation by abundant oidia production are main reasons for the commercial success of P. gigantea as Heterobasidion BCA in European countries (Pratt et al 2000). However, the restricted range of conifer species being protected by strains of P. gigantea requests identification of further BCAs for other tree species.…”

“…The strains of the products originate from the UK, Poland and Finland, respectively. Only Rotstop is a pro-duct of a single isolate (Pratt et al 2000). Recent reports of reduced performance of this Finnish strain in Sweden lead in year 2004 to the formulation of a Rotstop s variant with an effective Swedish isolate (Berglund et al 2005).…”

“…European and North American isolates are interfertile suggesting they belong to a single species, but some genetic differentiation including variations in the ITS (internal transcribed spacer) region has been encountered (Vanio & Hantula 2000, Grillo et al 2005. Formulations of own isolates have been applied in the USA for several years, but currently there is no state approval in North America for the use of P. gigantea as a pesticide (Ross & Hodges 1981, Pratt et al 2000.…”

“…Avoiding primary infection in healthy stands is therefore the target for biological control of Heterobasidion. Following early observations on strong antagonistic effects of the saprophytic white rot fungus Phlebiopsis gigantea towards H. annosum in colonising freshly-cut conifer stumps (Rishbeth 1963), the fungus has been applied for decades to stumps in the field for prevention of Heterobasidion infections (Pratt et al 2000). Throughout Europe, P. gigantea stump treatment is practised on more than 200,000 ha annually (Thor 2003).…”

“…This requires extensive research on ecological effects before licensing an agent for a specific environment -preferentially, the BCA should be of indigenous origin (for further discussion see Headrick & Goeden 2001, Lacey et al 2001, Shah & Pell 2003. In living tree and in wood protection, some biological control products of harmful fungi and insects have reached commercial Biological Wood Protection 275 production and application (van Frankenhuyzen et al 2000, Pratt et al 2000, Lacey et al 2001, Potter & Held 2002. In other cases, research to obtain ecological and economical viable products is actively ongoing (e.g.…”