Paul Markworth, Consulting Arborist
Over the past two years, southeast Wisconsin’s precipitation has been many inches below normal. We are in a drought and this drought is beginning to take its toll on our trees.
The first damage to a tree from drought is in the form of root damage. Absorption roots die back, limiting even more, the amount of water the tree can take up. In the worst case, a healthy looking tree can just die without much warning. (The lack of snow cover during the winter of 2011& 2012 allowed deep, prolonged frost to kill many additional absorption roots)
Second, radial growth of the trunk slows, new leaves are undersized, by mid summer leaves yellow and can appear scorched, and twig elongation becomes very short or non-existent. In an effort to keep the crown in balance with the declining root system, crown dieback and general thinning occurs.
Third, trees in a stressed condition are ideal candidates for attack by both boring insects and root rotting fungi. Both of these further damage the tree’s water conducting system, cutting off the water supply even more.
Drought aggravates matters for trees already under stress, like those surrounded by pavement, planted too deep, growing in compacted soils or dry slopes, defoliated by gypsy moths, and/or improperly planted or sited.
The aftereffects of a drought like this will ripple through the tree community for the next three to five years. We are already seeing an increase in Two-Lined Chestnut Borers in oaks, Bronze Birch Borers in birch, and Ash Borers and Apple Tree Borers in ash. Cytospera canker will again become epidemic in spruce, especially blue spruce. Many trees just will not survive.
It is impossible to keep every tree in good health during severe drought. Taking a proactive approach will make your trees more likely to survive. Watering, mulching and keeping diseases and insects under control may be the difference between keeping your trees around for you and your children’s lifetime or losing them in the next few years. Call your Wachtel Tree Science certified arborist to evaluate your trees for overall health and pest care management.