The Assessment of Chloride Injury from De-Icing Salts in Trees along State Highways in the Black Hills, Year 2

This project started in FY-07 and is being continued in FY-08. During the past several years there has been an increasing concern from the general public regarding the poor appearance and mortality of tree stands along the highways and roads in the Black Hills. The trees, almost exclusively ponderosa pines (Pinus ponderosa), were exhibiting stunted growth, needle chlorosis and burn, and shoot dieback. These stands generally have between 5 to 30 or more symptomatic trees along with several dead trees. Due to the proximity of these symptomatic trees to the road, many occur within 60 feet of the edge of the pavement, the primary suspect for the decline and mortality been road de-icing salt. A limited random sampling of symptomatic ponderosa pines was made during the summer of 2004. At that time foliage samples taken from trees along state highways 79 and 87 and analyze for foliage chloride content and the presence of picloram, a herbicide that can produce similar symptoms. Chloride levels in normal, healthy foliage and twigs are generally less than 0.1% (dry weight basis). Symptoms and injury of trees may occur when the internal chloride concentration rises above 0.3%. The foliage samples collected from symptomatic pines along the highways showed chloride levels of 0.47 to 0.63%. Picloram, a common herbicide used to clear weeds from roadsides, produces similar symptoms. The samples were also analyzed for this herbicide and only a few samples taken along highway 87 within Custer State Park had any detectable levels of this chemical. Herbicide applications do not appear to be responsible for the injury of roadside pines outside of the park but there is a high likelihood that de-icing salts, specifically chloride, is responsible for tree decline and mortality along state highways. The objectives of this research are 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 de-icing and roadside maintenance practices to minimize impact to roadside trees.


  • English


  • Status: Active
  • Funding: $44024
  • Contract Numbers:


  • Sponsor Organizations:

    Research and Innovative Technology Administration

    Department of Transportation
    1200 New Jersey Avneue, SE
    Washington, DC  United States  20590
  • Managing Organizations:

    Mountain-Plains Consortium

    North Dakota State University
    Fargo, ND  United States  58108
  • Project Managers:

    Tolliver, Denver

  • Performing Organizations:

    Dept. of Civil and Environmental Engineering

    South Dakota State University
    Brookings, SD  United States 
  • Principal Investigators:

    Ball, John

  • Start Date: 20070701
  • Expected Completion Date: 20190930
  • Actual Completion Date: 0
  • USDOT Program: University Transportation Centers Program
  • Source Data: MPC-281

Subject/Index Terms

Filing Info

  • Accession Number: 01460131
  • Record Type: Research project
  • Source Agency: Mountain-Plains Consortium
  • Contract Numbers: DTRT07-G-0008
  • Files: UTC, RIP, USDOT
  • Created Date: Jan 3 2013 1:19PM