Black Leaf Spot Damages Northern Sierra Aspen

A road trip to Lake Tahoe, then north on CA-89 from Truckee to Lake Davis weekend was an eye opener, this Labor Day weekend.

As previously reported, the “black leaf spot” fungus that has decimated quaking aspen groves atop Monitor Pass and in parts of the Hope Valley gets worse as you drive north on CA-89.  In some locations, aspen have lost all their leaves, while in most groves about half the trees have been affected.  This photo shows the contrast of a stand of aspen that has lost nearly all its leaves, near aspen and cottonwood that are full of deep green foliage.

What this means for the fall color spotter is that in areas where black leaf spot has hit, the show will be reduced by half.  Here’s a rundown of locations visited:

• Lake Tahoe (6,200′) from South Lake Tahoe (Camp Richardson) and along the west and north shores of Lake Tahoe, aspen are drier than seen in previous years, but the groves were not hit as hard by black leaf spot infestations, as seen at higher elevations south and north of the lake.
• CA-267 (Kings Beach to Truckee) – The stand of aspen that surrounds a weathered, one-room ranch house at 6,600′ (a popular photo workshop and wedding photography location) has lost many of its leaves. Some have begun turning.  The grove is dry. Willows are peaking orange yellow.
• CA-89 (Truckee to Sierraville) – Black leaf spot has hit aspen groves that grow beside the Little Truckee River at several points, with some groves completely denuded of leaves and the aspen look to be dead.  The healthiest trees are seen at Cold Creek Campground, though stands of verdant aspen are found near creeks and the river in all the campgrounds.
• Lake Davis/Portola – Aspen are dry but severe damage from black leaf spot was not noticed.

Weather conditions in late spring and early summer were ideal for the formation of black leaf spot fungus.  The U.S. Forest Service reports that, “Epidemic conditions are intensified by abundant rainfall in the spring and summer, possibly followed by warm temperatures for about 1 week.” That is exactly what happened this year.

Piled atop this unusual bloom of fungus in Northern Sierra aspen groves is that the effect of four years of drought is evident throughout the forest. Many aspen and alder leaves are dry and have very little flexibility. Ponderosa and Jeffrey pine, Douglass, white and red fir and incense cedar (such as at Alder Creek) appear stressed; bunches of brown needles are seen in many of the trees.

Our experience has been that where trees are healthy and robust, good fall color appears.  But, where trees are dry or diseased, the show is short-lived and disappointing.  If you enjoy visiting or photographing fall color in the areas mentioned in this report, time your visit when it peaks during a year like this one, when drought and disease have stressed the forest.

0 – 10% – Lake Tahoe – Aspen groves are just beginning to turn color.  Most of the groves are drier than usual, with some having lost leaves.

0 – 10% – CA-267 (Spooner Summit) – Willows are at full peak with orange yellow leaves.  Aspen have begun to lose leaves, some are beginning to show color change, black leaf spot fungus affects about a third of the stands, which are drier than usual.

0 – 10% – CA-89 (Little Truckee River) – Half the aspen have lost leaves or are afflicted with black leaf spot.  The remaining stands appear healthy and with full green foliage that should turn beautifully in early October.

0 – 10% – Lake Davis and Frenchman’s Lake – Aspen are drier than usual with some having been thinned out, though overall color should be good.