Assessment of Chloride Damage to Vegetation

Numerous complaints have been received recently concerning the discolored and dead trees along the edges of highways in the Black Hills. Chloride deicers have long been known to cause damage to roadside vegetation, primarily due to the chloride ions building up in plant tissues, either from root absorption or from roadside spray or aerosol collecting on foliage. Unfortunately, one of the most susceptible plant families to chlorides is the Pinaceae which means that the predominant tree species found in the Black Hills, ponderosa pine, is extremely susceptible to chloride-induced damage. A memo recently sent to State Foresters by Dr. John Ball, SDSU Department of Horticulture, Forestry, Landscape & Parks described the results of chloride analysis on ponderosa pine samples collected from along the roadside and reads in part, "…the samples we collected from browning ponderosa pines along the roads have been analyzed and here are the results. Regardless of the de-icing salts used, and there are many on the market, the primary toxicity issue is with the chloride component. Chloride, typically brought to the canopy by drift from salt-laden spray, is carried to the tips and margins of needles where it accumulates to lethal concentrations. Typical symptoms of chloride injury are browning needles and suppressed growth. Other ions in the de-icing salt, sodium and magnesium for example, can also injure plants but they enter and accumulate in tissue much slower so rarely are involved in tree decline and death. The normal value of chloride in foliar tissue is about 0.05% (dry weight basis). Symptoms appear when the internal chloride content is about 0.3%. The needles we collected along the road in various locations in the Black Hills ranged from 0.47 to 0.63%. I think we know why the trees are dying…." The situation is complicated by an existing infestation of pine beetles throughout the Black Hills. The Mountain Pine Beetle (Dendroctonus ponderosae) and Pine Engraver Beetle (Ips pini) are the two species primarily responsible for the damage. A 2003 Forest Health Highlight-South Dakota, produced jointly by the U.S. Forest Service and South Dakota Division of Resource Conservation and Forestry, listed 270,200 trees damaged by the Mountain Pine Beetle covering 189,700 acres as well as 120,700 trees damaged by Pine Engraver Beetles involving 45,200 acres. The bulk of this damage occurred within the Black Hills. Add to this the intermittent drought conditions throughout the Black Hills over the past several years and the likelihood of tree mortality becomes even greater due to combined stress. Research is needed to clearly delineate the effects of deicing in the Black Hills on pine trees adjacent to the roadside as well as the extent of any damages with respect to the surrounding forest. This project would provide the information necessary to modify current procedures to minimize impact, if necessary. The objectives of this research project will be to: (1) define the extent, distribution, sources and contributing factors involved in roadside tree damage and injury adjacent to highways in the Black Hills and (2) develop recommendations and guidelines for modifying current deicing and roadside maintenance practices to minimize impact to roadside trees.


  • English


  • Status: Active
  • Contract Numbers:


  • Sponsor Organizations:

    South Dakota Department of Transportation

    Transportation Building, 700 E Broadway
    Pierre, SD  United States  57501
  • Project Managers:

    Johnston, Dan

  • Performing Organizations:

    South Dakota State University, Brookings

    Department of Civil and Environmental Engineering
    Brookings, SD  United States  57007
  • Principal Investigators:

    Ball, John

  • Start Date: 20060401
  • Expected Completion Date: 0
  • Actual Completion Date: 20070228
  • Source Data: RiP Project 12709

Subject/Index Terms

Filing Info

  • Accession Number: 01458275
  • Record Type: Research project
  • Source Agency: South Dakota Department of Transportation
  • Contract Numbers: SD2006-01
  • Files: RiP, STATEDOT
  • Created Date: Jan 3 2013 12:39PM