Tough times for trees in our region
By Dan Wilcox, Outdoor Columnist
The dead red pines between River Falls and Hudson stand as brown monuments to last year’s drought. After a dry winter with little snow, the spring of 2012 started out with normal amounts of rain through June. July through November was dry and the soil profile was dusty in the fall. Many trees in our region suffered from desiccation last winter like the red pines on the gravelly moraine soils near Hudson.
Our winter that didn’t seem to end replenished the soil with snowmelt water as did above-average precipitation in the spring of this year. The May 2 storm that struck our area packed a nasty punch to trees by loading them down with heavy wet snow. Many branches and whole trees were snapped off and many tall thin trees were left with a permanent bend. We had to use a chainsaw to open up our driveway through the woods.
Weaker trees like box elder, quaking aspen, black willow and wild cherries suffered the most damage. Floodplains on the Kinnickinnic and the Rush rivers became jackstraw jungles of broken limbs.
The heavy rains in May and June saturated the soil. Thunderstorms and high winds toppled many large trees in our region. Big white pines and cottonwood trees in our neighborhood tipped over, their roots unable to keep them upright in the wet ground. Bursts of straight line winds left minor war zones across many acres of trees.
In the Twin Cities, the June 21 thunderstorms toppled thousands of trees from saturated soils, leaving behind hundreds of thousands of homes without electrical power. It took utility and municipal crews days to restore power and clear streets and sidewalks of downed trees.
The drought stress last year followed by a wet spring and storm damage left trees more vulnerable to disease. Butternut trees in our region are being devastated by an exotic disease that causes branch and stem cankers. The causal agent is a Sirococcus fungus that is thought to have spread from the southeast coastal region and first noticed in Iowa in 1967.
The rapid decimation of butternut populations is considered so severe that the U.S. Forest Service has listed the species as a “species of Federal concern.” Butternut trees in our woods are severely infected. We have harvested the larger dying ones for their beautiful wood but it doesn’t appear that there are many disease-resistant trees in the local population.
The wet spring and storm damage this year also accelerated infection of elms with Dutch elm disease. We had a bumper crop of morel mushrooms this spring that fruit under recently-dead and dying elm trees. Forest and urban populations of American elm have been devastated by two strains of Dutch elm disease that entered the country in unpeeled veneer logs from Europe. Elms dying of Dutch elm disease were first observed in Cleveland in 1930.
The spring storm damage also contributed to the spread of oak wilt disease. Oak wilt is caused by the fungus Ceratocystis fagacearum. All oaks are susceptible, but red and pin oaks are the most vulnerable. White and burr oaks are somewhat more resistant. Fungal mats form under the bark of infected and dying trees. Sap beetles are attracted to the fungal mats and transfer the fungus spores to live trees where they are attracted to sap oozing from storm damage wounds. Oak wilt fungus can also be transferred between individual trees by root grafts underground.
Despite the drought stress, storm damage and diseases, forests are resilient. The oaks, hickories and walnuts appear to be bearing a good crop of nuts this year. The prospects for reintroducing resistant American chestnut, butternut, and American elm into eastern forests appear to be promising. We look forward to planting some of those disease-resistant trees.
Please send any comments and suggestions for this column to me at firstname.lastname@example.org.