There are many reasons oaks decline. This has occurred throughout the range of oak in both forest and urban situations. It is not limited to any one species or species group. Incidences have been most frequent and severe among red, pin, and black oak in the red oak group and among white, bur, and chestnut oak in the white oak group. This is most notable in the central and eastern regions of the state. Oaks face many challenges in this state and this is a complex issue that has many factors such as biological and environmental, that creates unfavorable situations for oaks.
Trees are weakened by environmental stresses such as drought, southern exposure, waterlogging, shallow soils, or frost or by pests such as defoliating, wood boring, and sucking insects. Hypoxylon canker, and Armillaria root rot are some of the biological factors that play into decline. Weakened trees are then invaded and killed by insects and diseases that cannot successfully attack healthy trees. Decline is almost always associated with mature or over mature trees and stands. The red oak group is reported more often in the literature, but with the ever changing climatic conditions of this state both groups tend to decline. Hot and dry conditions in for the past couple of years may hasten decline in Kansas.
Signs & Symptoms
Trees affected by oak decline show a general advancement of dieback from branch tips – where leaves will sometimes still be attached, and epicormic sprouting along dominant branches and the main stem. Other symptoms include production of chlorotic (pale green to yellow), dwarfed, and meager foliage; and early fall leaf color and leaf drop. Often, there is a reduction in growth before the symptoms are superficial.
Links & Resources
- Oak Decline - US Forest Service
- Oak Decline: Why it's happening and what we can do about it - Missouri Department of Conservation
- Managing Oak Decline - University of Tennessee Extension