Over the last month or two, I have received a lot of emails and phone calls regarding eastern white pine (Pinus strobus) decline and dieback. Symptoms include yellowing/browing of the needles, sparse crowns, dieback, and even periodic mortality. Most of these symptoms appear gradually and even suddenly.
Even though eastern white pine is native to Illinois, this species is endemic only to the northern parts of the state on coarse textured soils with relatively low soil pH. Eastern white pine grows best on soils with good internal drainage (i.e., coarse loamy to fine loamy texture soils) and they are adapted to more acidic soils. We see the majority of eastern white pine decline problems on sites with heavy textured soils (i.e., high clay content) and with high(er) soil pH.
Ms. Nancy Pataky, plant pathologist at the University of Illinois Plant Clinic, noted that most of the eastern white pine samples submitted to the plant clinic showed no positive signs of pests or pathogens, though she noticed poor root growth and development. Ms. Pataky and Dr. Jim Appleby, a forest entomologist at Univ. of Illinois, are both under the impression that environmental stressors are playing a major role in statewide eastern white pine decline. Such environmental stressors include poor root growth induced by poor internal soil drainage (planting white pine on poorly drained soils); high soil pH; past drought events; heavy rainfall events; herbicide drift from adjacent agricultural fields; and hot and humid growing days. The combination of all these factors is believed to be contributing to this general eastern white pine decline throughout the state. Once the trees are stressed, the onset of subsequent pest and pathogen problems may ultimately follow.
So, what’s a homeowner to do? You can start by keeping your eastern white pines healthy as possible by mulching around the base of your trees, supplemental watering during periods of low/no rainfall, proper pruning to ensure adequate air movement through the branches and crowns of the trees, and the use of acidifying fertilizers if your soil pH alkaline or near neutral. Probably the most important take home message regarding eastern white pine decline is this, “Make sure to plant tree species that are physiologically adapted to your soils, site, and geographic location.”
Please refer to the following Websites for information on tree selection: