Entomophaga fungus, which thrives on late spring moisture, is one of the main natural controls of gypsy moth caterpillars. While 1999 was a good year for the oaks, it was a bad year for this fungus, thus potentially a good year for survival of gypsy moths. Decline of woody plants is complex, and the history, including the drought of 1999, should be factored into what we observe in 2000 and subsequent years. This spring and summer, when trees show leaf scorch and branch dieback, do not jump to conclusions and blame the last person who visited your landscape, be it the lawn-care company or the window washer. The cause of tree decline has a much longer pedigree.
Prevention is far easier than a cure.
You cannot prevent droughts, but you can limit many of the predisposing factors for decline such as competition for water and nutrients by choosing plants that are suited for their sites relative to soil pH, water, light and space requirements. Choose red oaks over pin oaks if your soil is not acidic enough. Avoid Japanese maples in sites with a history of verticillium wilt disease. Consider the mature size of your spruces when you plant them in a row to avoid root competition a few years down the line. Plant trees and shrubs that are adapted to our area.