Efficacy of Biological and Chemical Control Agents against Heterobasidion Spore Infections of Norway Spruce and Scots Pine Stumps on Drained Peatland

Abstract

Treatment of conifer stumps with a control agent effectively prevents Heterobasidion spore infections in summer cuttings and protects the residual stand and the next tree generation from damage caused by Heterobasidion root rot. Thus far, stump treatment experiments have been carried out in mineral soils, and no information is available on the efficacy of stump treatment agents in boreal peatland conditions. In the present study, biological and chemical control agents (Phlebiopsis gigantea and urea, respectively) were tested in Scots pine and Norway spruce stands subjected to thinning, cap cutting, and clearcutting on drained peatland in Central Finland. The control efficacy of urea was high in both spruce and pine stumps (on average 99.5 and 85.3%, respectively), while the efficacy of P. gigantea was highly variable on both tree species and ranged from full protection down to negative control effect, i.e., there were more Heterobasidion infections on the treated than untreated half of the stumps. The moisture content of the stump wood or the thickness of the peat layer did not affect the control efficacy of either control agent. These results emphasize a need for further studies to determine the reasons for the unsteadiness of the biological control in peatland conditions.

Afforestation of Land Abandoned by Farmers Poses Threat to Forest Sustainability Due to Heterobasidion spp.

“…Piri et al [99] tested the effects of P. gigantea and urea in Scots pine and Norway spruce stands after silvicultural treatments (thinning, topping, clearcutting) on drained peatlands in Central Finland. The effectiveness of urea was higher (average 85.8 and 99.5, respectively), while the effectiveness of P. gigantea was very different for both tree species and ranged from full protection to negative control.…”

Heterobasidion root rot infections on Scots pine : A cryptic threat to sustainable forest management in Sweden

“…Currently, stump treatment with spore suspensions of Phlebioopsis gigantea (Fr.) Jülich directly during thinning operations is the main effective method to prevent spore infection (Berglund and Rönnberg, 2004;Piri et al, 2023a;Zaluma et al, 2021). Phlebioopsis gigantea (Fr.)…”

“…Despite several studies demonstrating the significant effectiveness of P. gigantea treatment in preventing Heterobasidion spp. spore infection in pine forests (Piri et al, 2023a;, this approach is not currently implemented in Sweden. The utility of adopting stump treatment for pine forests warrants further investigation.…”

“…Various chemicals have been evaluated as stump protectants to prevent Heterobasidion root rot infections, but rea is the most widely used due to its high efficacy and stability Piri et al, 2023a;Zaluma et al, 2021). Application of urea on stump surfaces elevates the pH, making the environment unfavourable for basidiospore germination (Johansson et al, 2002).…”