Stubbehandling med pergamentsvamp och urea mot sporinfektioner av rotticka i bestånd av hybridlärk

Sammanfattning: Root rot is a big hurter and a huge economic problem for the Swedish and European forestry. The severest hurter is Heterobasidion annosum (Fr.) Bref and it occurs as two different species in Sweden. Commonly referred to as the P-type (Heterobasidion annosum s.s. (Fr.) Bref.) and the S-type (Heterobasidion parviporum Niemelä & Korhonen). Therefore a lot of research has been carried out in this topic to find a solution and reduce this problem, one alternative that have shown to be profitable is stump treatment in thinnings. Stump treatment is in the present situation a common method to reduce the infections from Heterobasidion annosum in stands mainly dominated by Norway spruce (Picea abies (L.) Karst.). Previously studies show that stump treatment with Rotstop® S and urea gives effective protection against Heterobasidion annosum in stands with mainly spruce. The Forestry in Sweden is today very dependent on tree species as Norway spruce and Scots pine (Pinus sylvestris), but in recent years the interest for other species has grown. One tree species that has become very interesting is hybrid larch (Larix × eurolepis Henry.), regarded as a fast growing species. Hybrid larch don’t differ from spruce when it comes to Heterobasidion annosum, it gets sever damages as well. The objectives with this study was to investigate if Phlebiopsis gigantea (Fr.) Jül. and urea works effective as stump treatments agents in stands with hybrid larch. The commercial names for the agents are Rotstop® S (Phlebiopsis gigantea) and PS-stubbskydd (urea). The investigation was made through field trials in stands with hybrid larch ready for the first thinning. The trials were established manually with help of a chain saw and spray bottle that were used for treating the stumps with the different preparations, during the summer 2008. Totally five different stands where used with 75 stumps in each. Of the total 75 stumps 25 of them where treated with Phlebiopsis gigantean, 25 with urea and 25 where left untreated as controls. The treated stumps were left for three months, thereafter discs were collected from all the stumps to be analysed at the laboratory. All discs where incubated in darkness for 7-10 days before the presence of Heterobasidion annosum in its conidial stage was registered.Heterobasidion annosum were found in all the stands in the trial, but the results had a big variance, which made the interpretation of the results very hard. Identification of the species showed that two different species of Heterobasidion, both P-type and the S-type were found in the trials as spore infections in the stumps. 65 % of the infections belonged to Heterobasidion annosum and 35 % were Heterobasidion parviporum. At two of the totally five sites many infections of Heterobasidion annosum were found with a variation from 4-75 % among the different treatments. At the other three sites there was a relatively low infection rate from 0-8 %. On the two sites with most infections urea showed a better effect than Phlebiopsis gigantea. Overall Phlebiopsis gigantea is showing better results than controls, but due to a great variation between sites no values are significantly different between treatments (p ≥ 0,1). Anyhow the result from this study clearly indicates that stump treatment with Phlebiopsis gigantea and urea is working on the two sites with most infections. Urea seems to have some advantage compared to Phlebiopsis gigantea.