Dissemination and Vectors

Long range

The long-distance transport of L. acicola is mediated by human activities. Trade with seedlings is the most often way of introduction into intact areas (Jankovský et al. 2009, Janoušek et al. 2016, Tubby et al. 2023). Considerable option is an inadvertent transport of infective needles by tourists. L. acicola is considered not to be seed-borne because the pathogen cannot survive on the surface of pine seeds for more than 30–34 days (Jianren and Chuandao, 1988). Therefore, long distance spread is probably not intermediated by seeds.

Short range

Warm and humid weather is particularly favorable for the development and natural spread of L. acicola. Conidia and ascospores are released throughout the year at temperatures ranging from –5.5 to 28 °C with a maximum temperature of up to 35 °C (Kais, 1971; Siggers, 1944; Wyka et al., 2018). The exact dispersal distance of conidia is not known, but similarities with Dothistroma suggest that conidia, and more likely rare airborne ascospores, may naturally disperse over 1 km (Mullett et al., 2016; Tubby et al., 2023). Germination does not occur at temperatures below 5 °C, although most strains survive and germinate soon after the temperature rises (Siggers, 1944). High levels of conidial dispersal are influenced by rain, but the distribution of conidia varies depending on the rainfall season in a specific geographic region (van der Nest et al., 2019).