Larch trees dropping needles

Western larch trees in the Metolius Basin are losing their needles - and it's not because of changing seasons.

Western larch in the Sisters Ranger District are suffering from a fungus known as "larch needle cast." The only deciduous conifer native to Oregon, western larch are commonly found along stream courses in the Metolius Basin and on Green Ridge.

According to Brian Tandy, silviculturist for the Sisters Ranger District, both larch needle cast and larch needle blight can affect the western larch. Although they are two different fungal diseases, the terms are used interchangeably.

"(The fungi) are favored by moist conditions in the spring, and this has been one of our most moist Mays ever," Tandy said.

Larch needle cast currently affects hundreds of trees in the Metolius Basin, possibly due to the high water table.

Tandy described the spread of the fungus:

"The disease over-winters in dead needles on the ground. In early spring, it produces spores which are windborn and can blow up into the tree, reinfect(ing) other needles. The fungus (grows) after the needles burst out of their buds in the spring. It starts in the lower crown (of the tree) and works its way up.

"It can take 80-90 percent of a mature tree, but the top stays green," Tandy added. "It rarely kills mature trees, but it will kill saplings."

Tandy said that chemical fungicides are ineffective at controlling the disease and are unpopular with forest users.

"It never gets to the point where we would deal with it (that way), and there's not a spray that works," he said.

Residents who wish to control larch needle cast on their own property may have some recourse.

"If individual homeowners wanted to do something, they could rake up needles in the fall and burn them, but this would only do any good if you had isolated (trees) in the yard," Tandy said.

Western larch are most easily identified in the fall, when the needles turn bright yellow, and in the winter when the trees are bare of foliage. In spring, the trees can be identified by the very pale green buds, which stand out from the darker evergreen conifers.

Other times of year, forest users can identify larch by its small bundles of 14 or more needles, papery cones and very straight open trunks.