Spruce Trees Are Suffering
Needle cast and wind take a heavy toll.
by Margaret A. Leary
From the August, 2017 issue
Winter is the time to hear and feel crunching underfoot. But it happened to me in May, on the sidewalk leading up to my front door. And the deck on the other side of the house, shaded by seventy-year-old trees, seemed sunnier than usual.
When I cleaned the deck, the cause of the crunchiness and the brighter sun stunned me: most of the needles were no longer on four spruce trees. They were on the deck, on its tables and chairs, and on the roof and its gutters. The stiff brown needles, tracked in by people and cats, pricked bare feet throughout the house. The trees had been green a few months earlier. Now the needles that hadn't fallen were brown.
Last year, I took a garden walk in Kent County led by MSU Extension educator Bob Bricault. He'd mentioned that spruce trees, especially the desirable Colorado blue spruce (picea pungens), were not doing well in Michigan. Now I went to the MSU website to learn more. Documents there explained that a fungus, rhizosphaera kalkhoffii, causes needle cast in spruce trees, but noted that other diseases can also afflict these beautiful conifers. Then I called Bricault.
"People love the blue spruce, but they really shouldn't plant it," he said. "The more we plant, the more possibilities for disease. The spruce decline is all over the state the last ten years." He added that needle cast can be slowed or prevented with the correct fungicidal spray.
Spruces were hit hard by the great windstorm on March 8, 2017. Wondering whether they might have been weakened by needle cast disease, I consulted John O'Connor, arborist with the Lumberjacks. Blown-over spruce trees, he said, were "about 95 percent of the total storm damage work we did." But "whether or not the tree was affected by a needle cast or tip blight didn't seem to correlate with whether it blew over."
Local landscape architect Chris Graham, who serves on the city's environmental commission,
had further insights into why so many spruces were felled by the 60 mph winds that hit Ann Arbor that morning. "In general," he explained, "conifers are defended here by leaves on neighboring deciduous trees, which act as a significant buffer to plants that have a high profile when the wind blows." But those trees hadn't yet leafed out in March, "and soil moisture levels were very high then, too. When that is the case, all trees have a harder time holding themselves down in wind. The ability of the roots to hold in wet soils is much less." He concluded: "Wind throw here comes down to the luck of the draw. The wind has to hit just right to catch a tree in its weak moment, direction, cultural condition, etc."
What if you want a blue spruce and don't want to take a chance on the Colorado blue or deal with the expense of anti-fungal treatment for the life of the tree? Graham said he has never planted a Colorado blue spruce but instead uses a concolor fir (Abies concolor) if someone wants blue foliage.
As for me, I arranged for my four afflicted trees to be removed and put four more on the watch list for next year. Since then, I've noticed suffering spruces everywhere: next door, across the street, on U-M properties, and driving country roads. I think about how, even after Bricault's warnings, the tree disease had sneaked up on me. I didn't really notice the problem until it hit my own yard.
After the trees come down, I'll refinish the deck, revel in the absence of those prickly needles, and fret about how to regain the shade the once-stately spruces provided for more than thirty years. Perhaps a no-maintenance, adjustable, sun-resistant, and naturally disease-free umbrella would fill the bill.
[Originally published in August, 2017.]
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