Larch needle blight

Hypodermella laricis

Larch needle blight is caused by the fungus Hypodermella laricis.  The fungus can kill both needles and spur shoots.

On this page

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

Description

Larch needle blight and larch needle cast can occur on the same host at the same time. All ages of western larch are susceptible to infection.

The fungus overwinters in dead needles on the ground. The fungus produces spores in early spring during larch bud break. Spores are spread by both wind and rain splash and these spores infect the newly emerging larch needles. Mature needles of larch are immune to the disease but new foliage will droop and prematurely change from green to reddish-brown. Younger trees may show an entirely affected crown while older trees will often show infection in the lower crown area.

Larch needle blight is primarily found in southeastern British Columbia.

Host tree species

The fungus infects all larch species, with western larch (Larix occidentalis) being the major host of concern in B.C.

Damage symptoms

Damage caused by the fungus first appears in June. Needles are discoloured over their entire length and all needles on a spur are usually affected. Small black fruiting bodies form on dead needles and infected needles will usually remain on the tree for a year before they fall off.

Western larch produces new needles in the spring so damage is typically limited to small growth reductions.

Identification images

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

Further Reading

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