Cause The fungus Hypodermella laricis infects newly emerging needles in the spring from dead infected needles that remain on the tree. More of a problem when spring and summer weather is cool and moist for years, or when larch grows on foggy, cloudy mountain sides.
Symptoms A red-brown discoloration of all needles on a spur occurs first. Shiny black elliptical fruiting bodies (hysterothecia) form along the undersides of attached dead needles. A distinct black line forms at the petiole end of the needle. Both needles and spur shoots are killed. Killed needles are retained after normal needle abscission. Severely infected stands have a brown, scorched appearance due to the persistence of the infected needles.
Cultural control
- Maintain open canopies in younger plantations.
- Use appropriate planting stock providence.
Reference Shaw, D.C., Oester, P.T. and Filip, G.M. 2009. Managing Insects and Diseases in Oregon Conifers. Oregon State University Extension Service. EM 8980.