Tuesday, October 7, 2008

Landscape - White Pine Decline Again This Year

We are seeing white pines dying in the landscape again this year. The following is information on why white pines die in the landscape.

White pine decline and white pine root decline are both causes of white pine death in the landscape. White pine decline disease is not infectious - it is associated with compacted soils, water stress, salt spray injury, air pollution injury, or high water tables. Berm plantings are particularly at risk due to the added stress.

White pine root decline disease is an infectious root rot, a progressive soilborne disease caused by the fungus Leptographium procerum, also called Verticicladiella procera. It can apparently occur anywhere white pines are grown, even on good sites.

White pine decline and white pine root decline symptoms are similar and both are common enough here that diagnosis could be confusing. From a distance, symptoms of gradual fading out and death of affected trees is very similar.

White pine decline symptoms begin gradually, often appearing in previously healthy plantings after the trees become 15-20 years old. Thinning of the foliage, needle tip necrosis, and wrinkling of the branches, is observed and suggests desiccation. Trees gradually turn brown and die. In a planting, scattered trees in seemingly random locations may die while others nearby remain green.

White pine root decline may begin with delayed candle emergence and elongation in spring. This can be followed by poor shoot elongation, needle browning, and lower branch death. Declining and dead pines may show patches of resin at the base, and when the bark is removed from the trunk and adjoining buttress roots, a resin-soaked dark brown staining or streaking may be evident in the cambium and wood. Infected roots several feet out from the tree may show lesions with cambial and vascular browning as these tissues are exposed when cut. Unearthing the roots using an air spade or air knife allows close examination of the roots. In addition, many diseased trees show excess resin flow from parts of the trunk where diseased branches had previously been removed. In some of the cases observed, white pine root decline appeared first in the wetter parts of the landscape, but it can also occur on well-drained sites. Even before obvious decline symptoms appear, trees may show reduced growth for a few years preceding decline.

Adapted from "DYING WHITE PINES - DECLINE OR ROOT DECLINE?" By John Hartman in the Kentucky Pest News from the University of Kentucky, College of Agriculture

No comments: