Problem with Pines

Browning pine trees and other evergreens have been a common sight throughout northern Illinois this spring. Much of the browning can be attributed to dry conditions since last fall. Pines, in particular white pines, have been under stress for some time, however.

Decline of white pine has been a common problem for the past few years. Many samples have been submitted to the University of Illinois Plant Clinic in Urbana. Laboratory culturing at the clinic has not found fungal disease pathogens as the cause. Few live roots have been found on the samples and this root decline may be due to several factors. Heat, drought, flooding and extremes in temperature and moisture are all possible causes of white pine root decline.

Site stress has also likely been involved in the decline of these trees. White pines planted on clay soils in exposed areas, such as a windbreak situation, often have problems. In some areas, heavy spring rains over the past years have saturated soils, which depletes oxygen. As a result, roots decline and die. Alkaline (high pH) soils can also stress white pines.

Dry soil conditions over winter combined with wind draw more moisture out of evergreens. In the case of white pines, if the tree already has limited roots, it will have a hard time replacing water lost from needles.

Mulching over the root zones can help retain moisture. Watering can also benefit when conditions are dry. But limited root systems may mean the decline continues, even if soil moisture is improved.

Keep in mind pines will produce new candle growth from terminal buds later this spring. In some cases, a pine that looks brown now may look much better by June when the new green growth emerges and helps mask the brown. Take a wait and see approach on pines; do not go out and prune them now, as the terminal buds will be removed and no new growth will occur on that branch.

Certainly other problems can affect pines, but this white pine problem is very common at the present time. If brown needles only show on one side of a pine facing a roadway, salt injury is a likely cause. Brown branches scattered throughout a tree could be problems such as fungal tip blight, insect damage or perhaps even mechanical damage. If a Scots or Austrian pine suddenly dies, it could be pine wilt caused by pinewood nematode.

Source: Bruce Spangenberg, Extension Educator, Horticulture
University of Illinois Extension

June 2000
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