Synthesis and New Observations on Needle Pathogens of Larch in Northern Finland

Abstract

Needle pathogens of larch (Larix spp.) in the Nordic countries are under-studied. Their incidence in Finland tends to be low and local, and this may be a function of enemy release, since species of larch were introduced to the region. Here, the ecology and incidence of larch needle pathogens and the abiotic factors that also affect larch in northern Finland are reviewed. Field observations and related laboratory analyses during the past 35 years have mainly been obtained near the Kivalo Research Area within the Arctic Circle, Finnish Lapland. The relatively recent introduction of Hypodermella laricis is a primary focus. This pathogen is not only new to Nordic countries, but can cause severe outbreaks, defoliation and crown-thinning in the canopies of all ages of most planted larch species worldwide. Symptoms of H. laricis clearly differ from those of Mycosphaerella laricina; the latter has affected Larix sibirica at high latitudes for decades. The effects of Meria laricis, Lophodermium laricinum, various rust fungi, and wind and frost are also discussed.

Keywords

• Larix
• Hypodermella laricis
• Mycosphaerella laricina
• Melampsora
• Melampsoridium
• rusts
• alternate hosts
• Betula
• Salix
• Alnus