According to the U.S Season Drought Outlook, while there will be some improvement in the central part of the country, the drought is likely to persist or intensify in the areas- especially in an area centered by the Rocky Mountains- well into the summer months. What can homeowners do to keep their tree healthy during hotter, drier summer months?
“While it’s impossible to keep every tree in good health in time of severe drought, taking a proactive approach for a prized or sentimental tree can support its good health,” recommends Peter Gerstenberger, senior advisor with Tree Care Industry Association. “A plan that is supported with good cultural practices, proactive monitoring for pests and disease, and response to warning signs is more likely to survive,” he says.
Silent suffering: A tree’s first damage from drought occurs beneath the soil line in the forms of root damage, long before any outward sign of trouble. After a tree’s unsuccessful attempts to conserve water by closing stomates, feeder roots die back, sometimes so drastically that the tree is unable to take enough water to support itself. In the worst case, a healthy looking tree collapses without much warning. More often, though, the signs of stress are much less dramatic.
“Radial growth slows,” explains Gerstenberger. “Leaves are undersized and may wilt, yellow, curl, or crinkle, well be marginally scorched, or even turn brown and fall. Emergent shoots are short. In an effort to right the imbalance caused by root-loss, crown dieback or a general thinning of the canopy occurs.”
Opportunistic pests and diseases: That’s when “opportunistic” pests make their move. Boring insects are thought to be drawn by the odors and acoustic signals of stressed trees. The sound of water columns breaking cues the borer to invade the tree and lay eggs. Gerstenberger recommends taking preventative action by applying treatment by spray or injection to protect prized or important trees from borers because, “ by the time we realize the tree is stressed, it’s been heavily riddled and girdled.”
Another danger to stressed trees in fungus, which makes initial contact with surface roots. Gerstenberger notes that when a chemical change in the tree signals a weakened state, the fungus penetrates the bark, wood and cambial zone with fan-like, leathery clumps, cutting off the water supply to the tree.
While all trees are at risk during long period of drought, some are more prone to its effects. New transplants are highly vulnerable to drought stress, and supplemental watering for the first few years of established is necessary, to extent that it’s allowed. But even mature trees are suffering