3 Common Tree Diseases that Can Devastate A Grove


Tree care experts in Seattle share signs and solutions for common tree ailments.

Stop these Tree Diseases in Their Tracks by Noticing Early Signs

All living things can be affected by disease, even trees. Fungal, bacterial, and viral infections are their biggest threat. Washington state is known for its forests and therefore must pay special attention to prevent the spread of arboreal diseases that can destroy a large portion of trees at a time. 

This article will discuss five such deadly diseases, their causes, their preferred victims, and the solutions for better tree health.

Armillaria Root Disease

This particular fungal infection, also known as shoestring root rot, can show up in both living and dead trees. It usually starts by feeding off dead wood and then spreads to healthy trees, often attacking the root system where it’s difficult to detect.  It can inhibit growth and eventually be deadly for the infected tree.

The Bottom Line:

  • Cause: A family of fungi classified as Armillaria. There are several species within this classification, but the most common one is Armillaria mellea.
  • Favored Trees: This parasite does not limit itself, but has been detected in both conifer and broadleaf trees and can feed on both living and dead wood.
  • Most Common Occurrences: This is widespread throughout the United States and goes by many names depending on the type of tree it infects.
  • Signs: White, moldy-looking growth on the trunk, mushrooms sprouting around the roots of the tree, or yellowing foliage on the crown of the tree.
  • Solutions: Because this fungus is so prevalent and can live on anything, eradicating it may be very difficult. Antifungal solutions can be applied, but it should be monitored closely by a tree care professional.

Dothistroma Needle Blight

This blight is likewise caused by a fungus and has caused havoc on the plantings of Ponderosa pines in the eastern states.

The Bottom Line:

  • Cause: The fungus called Dothistroma pini is the reason for this deadly tree disease.
  • Favored Trees: Dothistroma needle blight, as the name implies, attacks a wide variety of pines including the ponderosa pine and the Austrian pine.
  • Most Common Occurrences: It has caused infections mostly in adult trees and has been seen throughout the upper midwest and across California, Oregon, and Washington.
  • Signs: Dark green bands on needles followed by brown bands and spots are the main early indicators of this needle blight. The next steps are defoliation and death of the tree.
  • Solutions: There are fungicides that work quite well on Dothistroma, but there are correct ways to apply them and an arborist should be consulted.

Laminated Root Rot

This is yet another fungus that is native to the Pacific Northwest and tends to infect trees in small clumps. It can easily spread from tree to tree and cause damage to a larger area.

The Bottom Line: 

  • Cause: Phellinus weirii is a fungus that lives throughout the northwestern U.S. and parts of Canada. It has been detected as far as Japan.
  • Favored Trees: This fungus primarily attacks certain species of conifers such as white fir and douglas fir. It can easily pass from deadwood to living wood through the roots.
  • Most Common Occurrences: It effects trees of all ages and sizes and can inhabit a wide variety of hosts. Hardwoods seem to be immune.
  • Signs: If the crown of the tree begins to yellow and growth seems inhibited, this may be an initial sign of laminated root rot. Some trees do not show signs soon enough and merely fall over from rotting roots.
  • Solutions: Because this fungus can live in dead material and is passed by the root systems, sometimes the only solution for the health of the surrounding trees is tree removal. Always consult a tree service company when considering tree pruning or removal.

About Seattle Tree Care

For the past fifteen years, Seattle Tree Care has been passionately caring for the arboreal health of the greater Seattle, WA area. We are ready to advise you on both commercial and residential needs. Call today for a consultation with a certified arborist.

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