Forest Insect and Disease Newsletter

Symptoms of Annosum root disease

By Linda Williams, Wisconsin DNR-Forestry, Green Bay

photos: Symptoms of Annosum root diseasePockets of mortality in pine plantations should be examined for the presence of annosum (Heterobasidion irregulare). If fruiting bodies are present they will be at the very bases of trees or old stumps from previous harvests. You may have to pull back the duff layer to see smaller fruiting bodies, which will look somewhat like a shelf fungus and will have a white or cream-colored lower surface which under magnification is pitted (photo below). Other symptoms can be quite variable but you may see the following:

  • Understory species that are being killed by annosum, which can kill all conifers and some hardwoods as well. If understory is being killed you may be able to find fruiting bodies on these young trees.
  • A pocket that may look like a "typical" pocket, with dead trees in the center and fading/dying trees on the edges.
  • A pocket that may look like a clearly defined area of mortality that you might mistake for a lightning strike or a bark beetle pocket.
  • Fruiting bodies, or you might find them only on old stumps, only on dead understory, or only on recently dead trees.
  • Fruiting bodies that are large, shelf-like fungi, small popcorn-like spots, or the flat form (which I seem to find more commonly on white pine).

The point is, pockets of annosum that I have visited have had highly variable symptoms, so if you see dead pines I would highly recommend that you examine them more closely to try to determine if annosum was the cause of the mortality. If you find annosum in the northeast region please let me know.

Annosum, winter stump treatments – recently an email from the State Forester and an email from Kyoko Scanlon, the DNR State Forest Pathologist, were sent out addressing the questions of treating stumps during the winter to prevent new annosum infections. Although the risk of getting new infections of annosum is very low during the winter it is still possible and stump treatment should still be explored for all conifer harvests. The manufacturer of Cellu-Treat is in the process of changing the label to allow the use of an additive that will act as an anti-freeze, but until the label is changed what can you do? Here's what Kyoko suggests you consider:

  • map: Wisconsin Map showing counties affected by annosum root disease

    Confirmed counties in WI with annosum root rot (as of November 2010) WDNR

    Consider the use of Sporax. Sporax is a granular material that can be applied on fresh cut stumps to prevent annosum root rot. It will have to be applied manually.
  • Explore the possibility of adjusting lines and the solution tank to keep the Cellu-Treat solution from freezing. The manufacturer of Cellu-Treat has suggested that a heat element be used around a tank and wires be placed near hydraulic line. Unfortunately, at this point, such attempts have made only limited success.
  • Consider postponing the harvesting until the temperature increases above freezing (32F) when the solution will not freeze.
  • Consider risk and economical benefit analysis. When the daytime temperature does not reach above freezing (32°F), and the forecasted temperatures for the next 10 days are not predicted to exceed 40°F, it is considered very low risk for infection. Especially if there is over one foot of snow on the ground, the majority of the conks will be covered under the snow and will not disseminate spores. Can a landowner/property manager accept low to very low risk and harvest pines this time of the year without treatment? It is important that a landowner/property manager understands the risks of introduction and benefit prevention to make a decision.

More information on annosum. Don't wait for annosum to show up in your stand or your county to take action!