The Drought, Act II

Michael Raupp, an entomologist at the University of Maryland, said the drought's timing couldn't have been worse for hardwoods attacked last spring by the gypsy moth caterpillar. Dry conditions in May and June were not conducive to trees refoliating. This double whammy of leaf loss and drought stress set up the ideal conditions for borers. In addition, gypsy moth egg masses surveyed over the winter portend an even worse outbreak this spring in much of Maryland.

"There are so many doomed trees right now," Raupp said. "They will push out leaves in the next month or so, but they are so heavily infested [with borers] they'll die over the course of the summer."

Systemic insecticides can be used to kill the larvae, but trees with excessive dieback in the canopy may have a compromised vascular system that cannot transport the pesticide to where it will work, Raupp said.

Of course, not all the damage will be as dramatic or irreversible, especially if the gardener follows some sound practices.

First, make sure that the root zone is covered with a two-inch layer of organic mulch, which will conserve soil moisture. Over several months, the mulch will decay and help feed the beneficial microbial life in the soil. Make sure that you, or your landscaper, avoid the common but harmful practice of piling mulch against the base of a tree trunk. The larger the mulched areas, the more effective the covering, because the feeder roots of a mature tree reach well beyond the canopy. A broad area of mulch also keeps turf grass away from trees. Fertilizers and pesticides used on lawns, as well as lawn watering regimes, may harm trees.

Also, do not apply excessive amounts of fertilizers to trees and shrubs this spring. Stressed trees given high nitrogen feeds can actually expend energy processing the nutrients, resulting in "a net decrease in the reserves of that tree," Bastian said.

And although you want to keep root zones occasionally and deeply watered when it turns hot and dry, over-watering could well rot the roots. Most trees benefit from an occasional deep watering in hot, dry weather; let the top inch or so dry out before returning.

The drought does bring a few silver linings: Populations of lawn grubs and black vine weevils should be down this year, Raupp said. And the crisis reminds us to make better decisions about what, and where, to plant this spring. The trees and shrubs most harmed by the drought were already compromised by growing in poor soil and in locations ill suited to the particular plant. Pick a plant suited to its intended spot, nurture it, and build the soil as the root zone expands over the years.

Bastian offers another stratagem: "Cross our fingers and hope we don't have another drought."