Larch needle cast

Rhabdocline laricis

Larch needle cast is caused by the fungus Rhabdocline laricis (formerly Meria laricis) and it affects all species of larch (native and introduced) in North America. 

On this page:

• Description
• Host tree species
• Damage symptoms
• Identification images

Description

In most instances larch stands do not experience serious damage from larch needle cast infection even though the disease may appear to be causing a significant amount of foliage mortality. However, larch needle cast can kill nursery seedlings.

The fungus overwinters in dead needles, either on the host or on the ground. The fungus produces spores in early spring when larch breaks bud. Spores are disseminated by wind or rain splash and infect newly emerging needles. As moisture conditions favour new infections, the fungus may continue to infect needles throughout the summer if moisture conditions are favourable.

Host tree species

All larch species, both native and introduced, in North America. The native larch in British Columbia is western larch (Larix occidentalis).

Damage symptoms

Needle discolouration usually only occurs on part of the infected needle and often appears first at the tips and spreads downward. Not all needles on each individual spur are affected. Needles in the lower portion of tree crowns are affected first.

Identification images

Visible larch needle cast (brown spots on the needles) and larch needle blight (brown needles and dead tufts of needles).

Further Reading

Read more about larch needle cat in the Field Guide to Forest Damage in B.C. (PDF, 6.6MB)