Biological control of Heterobasidion root rot of coniferous stumps by Phlebiopsis gigantea – literature review | Phlebiopsis gigantea skujkoku celmu bioloģiskajā aizsardzībā pret Heterobasidion annosum s.l. izraisīto sakņu trupi – literatūras apskats

拉脱维亚语. Sakņu piepe Heterobasidion annosum s.l. izraisa sakņu trupi, kas īpaši izplatīta skujkoku audzēs. Sēnes izplatību veicina pēc mežizstrādes atstātie svaigie celmi, kas viegli var inficēties ar H. annosum sporām. Apstrādājot celmus ar bioloģiskajiem vai ķīmiskajiem preparātiem, ir ierobežojama celmu inficēšanās ar H. annosum. Bioloģisko preparātu izmantošanu nosaka celmus kolonizējošo sēņu sugu antagonisms un konkurence par substrātu. Lielā pergamentsēne Phlebiopsis gigantea ir vienīgā sakņu piepes ierobežošanai komerciāli pielietotā sēne. Eiropā plaši izmanto Somijā izstrādāto preparātu “Rotstop”, kas nodrošina priežu celmu aizsardzību pret H. annosum, bet ir mazāk efektīvs egļu celmu aizsardzībai. Minētais preparāts lietošanai Latvijā reģistrēts 2007. gadā, un to izmanto krājas kopšanas cirtēs. No 2006. gada Latvijas Valsts mežzinātnes institūtā “Silava” tiek veikti pētījumi, lai perspektīvā celmu aizsardzībai izmantotu preparātu, kura sastāvā būtu P. gigantea Latvijas izolāti.

英语. Heterobasidion annosum s. l. causes root and butt rot of conifer and to a lesser extent of deciduous trees. In Latvia, direct losses caused by H. annosum, as reduced quality of spruce wood, are estimated to be as high as 750 LVL haE-1. Fresh conifer stumps right after felling provide a good substrate for airborne spores and favour the spread of H. annosum. It is possible to reduce the spore infection of stumps by ca. 90% or more by treating fresh stump surfaces with biological or chemical protection agents, most commonly used chemical agent is 30% urea solution. Biological control is based on antagonism and competition between the organisms living in stumps. Currently, wood-decaying fungus Phlebiopsis gigantea is the only commercially used biological control agent against Heterobasidion root rot. P. gigantea colonises the stump surface and prevents its infection by H. annosum spores. P. gigantea is a fairly common fungus in conifer forests, and a number of genetically diff erent strains of this fungus can occur in the same stumps. Different commercial preparations of P. gigantea are used in the European Union: Rotstop® in Fennoscandia, PG suspension® in the UK, ‘PG IBL’ in Poland and Rotex® in Germany. Rotstop provides good protection against H. annosum in pine stumps but is less effective in spruce ones. Its efficacy in different stump treatment experiments carried out in Latvia was 20-79% for spruce and 54-100% for pine. The preparation Rotstop was registered in Latvia in 2007 for treating pine and spruce stumps. Its use costs 0.27-0.82 LVL mE-3, depending on tree diameter. The preparation costs make up 54% of the total costs of treatment. Stump treatment has a variety of economical and ecological benefits. In Latvia, the incidence of root rot in spruce stands increases with the stand age: in 41-60, 61-80, and 81-100 year-old stands the incidence is 15.7%, 21.7%, and 24.5%, respectively. According to the estimates, providing the current silvicultural methods continue to be used, in future the incidence of root rot is expected to increase 1.38 times while the stands shift from the age class of 41-60 to that of 61-80 years, and again 1.13 times till the cutting age (81-90 years). Assuming that the decay frequency of spruce at the age of 41 years is 15.7% and the efficiency of stump treatment with Rotstop is 80%, the decay frequency at the time of final felling will be 17.3% in case the stumps are treated, and 24.5% without treatment. Costs of treatment during thinning operation are 39 LVL haE-1. Assuming that the time of investment is 40 years, the reduction of losses is 750 LVL haE-1 (750 LVL • 17.3 ÷ 24.5 = 200 LVL haE-1), which makes approximately 4.4% rate of return. Earlier research has shown that the Rotstop has no significant effect on the environment. However, from the point of view of biological diversity, it is better to use the native strains of P. gigantea in biological preparations. As the field experiments of stump treatment are laborious the preliminary testing of P. gigantea strains was carried out in laboratory. Unfortunately, the results obtained in laboratory tests do not always correlate with those in forest. However, some essential characteristics of P. gigantea strains can be tested in laboratory. For instance, abundant spore production is important for effective formulation of the preparation. Besides, one of the most important characteristics 27 of an effective P. gigantea strain is its growth rate in wood which can be tested in laboratory. Since 2006, experimental work is carried in the Latvian State Forest Research Institute „Silava” to find the native isolates of P. gigantea that could be used for stump treatment in Latvia. Results obtained in this research show that some of the Latvian P. gigantea strains are as effective as the Rotstop strain. During evaluation of the growth rate of P. gigantea in wood, new method was developed that allows screening up to 15 strains in the same piece of log.