John Ball, SDSU Extension Forester and Forest Health Specialist for the South Dakota Department of Agriculture comments on the droughty conditions and the effect on trees.
"The most common symptom of moisture stress is leaves turning a lighter green than is typical for the species. Affected leaves are also showing brown and crisp margins, with browning often occurring between the leaf veins," Ball said. "Some trees in the southeastern part of the state are already having leaves curl and fall, a symptom of severe stress. Eventually trees showing severe moisture stress will begin to die back."
In current drought conditions, evergreen foliage on drought-stressed trees, particularly seedlings, is turning yellow to almost purple at the tips of the needles. Some of the older needles, which were formed three to five years ago, on drought-stressed trees are beginning to drop prematurely.
"There is not much that can be done at this time other than water," Ball said. "This is particularly important for new plantings, whether they are seedlings in a new windbreak or a tree just planted in a yard."
He says a seedling is going to need between a pint and a quart of water per day, while a newly planted tree will need about 2 to 3 gallons per day at this time.
"Most young tree belts are probably not receiving anywhere close to this amount and I suspect there will be a lot of replanting next spring," he said.
Ball says established trees will not need daily watering, but still require weekly watering to survive this dry, hot summer. A 2-inch diameter tree, as measured at 6-inches above the ground, should be receiving about 20 gallons of water a week.
"This is best-applied slowly with a soaker hose placed near the tree," he said. "Tree roots typically extend out as far as the tree is tall, but the critical watering zone is a distance out about two-thirds the height. As an example, if the tree is about 24-feet tall, the watering should occur within 16 feet of the trunk."