Description:
Causes of mortality of containerized western larch seedlings at the Champion
Timberlands Nursery, Plains, Montana, were investigated. Seedlings were rated
for disease severity based on extent of foliar decline symptoms and fungal
isolations made from their roots. Isolations were also made from selected
larch seed. Consistent associations between root colonization by potentially
pathogenic fungi and level of disease symptoms were not found. Fusarium spp.
were only isolated from a few seeds and seedlings sampled toward the end of the
growth cycle. These fungi were also frequently isolated from asymptomatic
seedlings. It was concluded that heat injury which occurred during the spring
when tissues were sensitive was the most likely cause of seedling mortality.