Drought hits SE counties

When a drought sets in, trees suffer from lack of water (leaf scorch) and become susceptible to attack by a number of opportunistic insects and diseases. Besides the leaf scorch on bur oaks, maples, and ash, we have seen bronze birch borers on birches, two-lined chestnut borers on oaks, bark beetles on pines. These opportunistic insects have developed the ability to detect trees under stress. Studies have shown that two-lined chestnut borer adults are able to rapidly and specifically locate stressed oaks in stands containing stressed host species. Stressed trees also have less energy and resources to defend themselves once attacked.

What to do now?

The best way to care for your drought stressed trees is to water them. This is especially true for newly planted landscape trees (planted within the last five years) and for all landscape trees growing on drier soils. A good fall watering may help prevent possible winter injury, as most of the types of winter injury are the result of desiccation.

Woodlot owners should survey their woods early next year as trees begin to refoliate to check for oak mortality and losses in other species.

Trees with sufficient water are not as attractive to many of the insect pests. Also they can mobilize more energy to protect themselves if they are attacked. Trees should receive one inch of water per week during the growing season either from rain or watering. One good soaking is better than two or three light sprinklings. Light sprinklings actually benefit your grass more than your trees. Lay the hose on the ground and let it soak into the soil. If using a sprinkler set an empty tin can out so you can catch and measure how much water you are applying.

Some other recommendations to help trees stressed by drought include the following:

  • Mulch around the trees. This conserves moisture and adds organic matter.

  • Avoid using herbicides around your trees. This includes products like "weed and feed". Most herbicides used on lawns kill broadleaf plants and your hardwood trees are broadleaf. These herbicides should not kill your trees if applied according to label directions but may put additional stress on the trees.

  • Avoid using fertilizer this fall. Fertilizing may stimulate growth when it is better for trees to acclimate to the fall, and gradually reach dormancy.

  • Avoid wounding trees. Trees expend energy repairing wounds that could otherwise be used to prolong their lives.