Trees under stress
SUMMIT COUNTY – When Rick Herwehe examines trees in various neighborhoods throughout the county, he sees brown and fallen needles – all the result of three years of drought stress.
When the arborist plunged a moisture meter into the ground, it read zero; it should read at least two. In a patch of sod under a tree, the meter read “OK,” he said, but two inches down, it read zero. And all the trees were dead.
“In the urbanized soils, the trees have lost their organic matter, the soil is compacted, water doesn’t settle and infiltrate the soil – it lands on top and runs off,” he said. “I’m seeing a lot of brown needles, a lot of stunted growth. They’re suffering from internal drying; they’ve popped their buds, and those have died. Needles are turning brown.”
Although it can take up to two years before signs of drought injury appear, typically the first thing to occur is wilting, scorched leaves that fall early in the season and make the tree appear thin and sickly, Herwehe said. Evergreen trees present brown needles at the top of the tree and at the ends of branches.
That’s when the bugs can move in.
“I can tell you it’s getting worse,” said Kevin Williams, forester with the Colorado Forest Service in Granby, which covers Grand, Eagle and Summit counties. “Beetle activity is on the rise.”
The worst place he’s seen in his three-county area is around Ute Pass at the north end of Summit County, where “almost all the trees are dead,” he said.
“There are twice as many bug-infested trees at The Ranch at Keystone than we have had any other year,” he said. Other areas where bugs have a toehold include a hillside near the county landfill and at the southeast corner of the Frisco Peninsula.
There are a few ways to control beetle spread, but it may be too late for this year, Williams said. The beetles began their annual flights in early July and will continue to spread from tree to tree through August. The only way to thwart them is to remove the infected tree before the bugs leave.
“One year’s tree can infect at least another two trees,” Williams said. “And in times of drought, beetles are more likely to successfully attack the tree because it’s stressed and more susceptible to everything.”
Thinning trees increases the vigor of the stand and makes the remaining trees healthier because they’re not competing for nutrients.
Pine beetle infestations are more common in Summit County, but ips, spruce and balsam fir beetles also could flourish in times of drought. Aphids, which show up in cottonwood and aspen trees and attacked local trees last summer, have yet to make an appearance this year, Herwehe said.
Recent rainfall hasn’t helped as much as hoped, either.
After what many perceived as a “substantial rainfall” in early July, Herwehe laid his moisture meter atop the duff on the ground and got “a blip.” Just under that, the meter read zero.
Trees soak up as much water as they can when it rains, said Jon Harrington, owner of Alpine Gardens, who farms trees in Park County and in the northern end of Summit County.
“Trees that should have budded out by May 15 budded out at the end of June,” he said. “They were doing nothing. And the minute there’s rain, the buds break open in days. They went from tight buds to needles. Even the trees at the nursery budded out way late. It seems kind of strange they’d bud so late in such a warm spring – and when they’re on irrigation.”
If the drought continues next summer, Herwehe said people should expect to see more beetle infestation – and more dead trees.
Jane Stebbins can be reached at 668-3998 ext. 228 or firstname.lastname@example.org.
Tips to healthy landscaping.
? Organic fertilizers are available that absorb several times their weight in water.
? Mulching reduces evaporation.
? Low-water, high altitude, mountain grass mixes are hardier, go dormant and green up when water becomes available again.
? Lawn aeration gets oxygen to the roots, enabling the lawn to absorb water better.
? Water deeper and less frequently. This encourages the development of deeper root systems, which make for stronger plants. Water lawns once every two to three days – maximum.
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