Occurrence of several needle pathogens in young forest stands of scots pine in Latvia

This study aimed to investigate the spread of several needle pathogens from the genera Dothistroma, Diplodia, and Lecanosticta that have been introduced to Latvia in recent decades. The occurrence of these pathogens was assessed in 165 forest stands of Scots pine (Pinus sylvestris L.). Stands were selected across Latvia based on stand composition (pine monocultures), stand age (up to 20-year-old pines), and an approximate area of one or more hectares. Stands were surveyed during either the spring or autumn of 2021. The needle cast rate was determined in each stand by inspecting 10 random trees and collecting one representative sample from three symptomatic pines. Needle pathogens were identified based on morphological characteristics and molecular analysis with species-specific primers for four pathogens: Dothistroma septosporum, Dothistroma pini, Diplodia sapinea, and Lecanosticta acicola. The analysis revealed that Dothistroma septosporum and Diplodia sapinea were the most common pathogens found in 30% and 18% of stands, respectively. L. acicola was not detected in any of the analysed samples. Since all tested pathogens are recently established in Latvia, monitoring their spread and impact to local forests is important. This work was funded by JSC Latvia’s State Forests (project No. 5-5.9.1_007f_101_21_69) and Forest4LV (project No. VPP- ZM-VRIIILA-2024/2-0002).