Friday, August 10, 2012

More on Canker Rot in Hardwoods


Cover photoI've been blogging about some common tree disease that can really cause some harm to your trees. I recently posted about cankers, but this post has even more useful information.  Cankers can be detrimental to a tree's life, so it is important to know exactly what they are and what to do about them if your tree develops cankers.

Canker-rot fungi cause serious degrade and cull in hardwoods, especially the red oaks. This is especially common in the south, but trees in every region of the US are susceptible.  Heartwood decay is the most serious form of damage, but the fungi also kill the cambium and decay the sapwood for as much as 3 feet above and below the entrance point into the tree. The ability of these fungi to kill the cambium and cause cankers distinguishes them from fungi that are restricted to the heartwood. 
Two fungus species in the family Polyporaceae and one in the Hydnaceae are primarily responsible for canker-rots. The diseases are commonly called hispidus canker, spiculosa canker, or Irpex canker, depending on the causal fungus. 

Canker-rots are most important on the red oaks, but also occur on hickory, honeylocust, some white oaks, and other hardwoods. Hispidus canker, caused by Polyporus hispidus, appears most frequently on willow oak and water oak in bottomlands and occasionally on Nuttal oak, white oak, and hickory. Spiculosa canker, caused by Poria spiculosa, is most common on willow oak, water oak, and honeylocust in bottomlands, and on hickory in uplands. A similar canker caused by Poria laevigatta is found on bottomland red oaks. Irpex canker, caused byIrpex mollis, most often attacks red oaks in both bottomland and upland areas.

Spiculosa cankers are less common than hispidus cankers. 

The rot associated with spiculosa cankers increases in length at about 10 inches per year.

The decay under Irpex cankers extends up and down from some cankers as much as 8 feet; however, the rate of decay is unknown.

Life History and Habits
Like most wood-rotting fungi, those causing canker diseases reproduce from microscopic spores. Spores, produced and released by conks (sporophores), are distributed by the wind. Those that lodge on wounds of susceptible hosts may germinate and start new infections. Canker-rot fungi generally enter through branch stubs and grow down these stubs into the heartwood. They also spread out from the point of entry, killing the cambium and forming progressively large cankers.
Hispidus cankers are usually elongate, large, and conspicuous. When the cambium dies, a callus fold forms around it; but the callus tissue is killed in 2 to 3 years by the spreading fungus. As additional callus folds are formed and killed, the tree frequently develops a spindle-shaped swelling that continues to increase in size (see below). The central part of the infected region is sunken and covered with bark. The remnant of an old branch stub, usually less than 1 inch in diameter, can frequently be found near the center of the canker. On young cankers the branch stub itself is often present.
Figure 1Hispidus canker and conk on a Nuttall oak.
Hispidus conks are 2 to 12 inches or more wide. They are spongy, hairy, stalkless, and yellowish brown to rusty red. The lower surface has small round pores. The conks form from July to October and produce large quantities of spores daily for up to 21 days. Spores are dispersed in all directions from the conks; most travel no more than about 140 yards and movement is usually horizontal and downward. After a few months the conks dry to a black mass and fall to the ground. Behind the cankers the entire heartwood is decayed. The decay is called a white rot because the wood is delignified and becomes soft and straw-colored to pale yellow.
Figure 2
Spiculosa canker on a young willow oak.
Spiculosa cankers appear as rough, circular swellings on the bole, usually with depressed centers (see right). Evidence of an old branch stub generally can be found in the center of the canker, where branch wood has been replaced by brown, sterile fungus material. Although cankers are small, infected branch traces are much more swollen than uninfected ones. Conks ordinarily do not grow on living infected trees; they develop on well-decayed logs or snags. They grow flat under the bark of the dead tree and, as they develop, push off the bark to expose the brown fruiting surface. Doubtful spiculosa infections can be identified by chopping into the center of the suspected branch trace. If infection is well established, the brown fungus material will be revealed by the ax-cut. The entire heartwood behind the canker always shows white rot (see below).
Figure 3.A cross-section of willow oak shows the rotten heartwood caused by a spiculosa canker.
Irpex cankers are more irregular in shape than the other two kinds. They usually have a branch stub at or near the center and a number of sunken areas on the swollen margins. Conks and white fungus material often occur on or near the base of the sunken areas (see left below). The conks are small and creamy white with short, jagged teeth on the lower surface. Large numbers of spores are produced mostly at night for 10 days or longer during the summer. Irpex cankers are usually smaller than hispidus cankers, but some are up to 2 feet long. There is always white rot in the heartwood behind these cankers (see right below).
Figure 4Irpex canker and conks on willow oak.Figure 5 A cross-section of a willow oak showing rotten heartwood caused by Irpex canker.
Control
Canker-rot fungi infections develop rapidly and quickly convert trees into rotten culls. Cankered trees should be cut as soon as possible to salvage usable material and to provide growing space for sound trees. These fungi can produce spores on dead standing trees for several years. Felling culls limits spore discharge and dissemination, thus lessening the danger of infecting adjacent trees.

If you are concerned about your trees for any reason, please contact Trees "R" Us, Inc.  Trees "R" Us, Inc. has 4 certified arborists in their plant health care division that are well trained on how to give your trees and plants the proper care they need.  Contact us for an analysis of your trees and plants.

Trees "R " Us, Inc. is proud to educate our communities on proper tree care and maintenance.

It is through education that we really save trees and help the environment.  We hope you found this post informative and educational. 
Trees "R" Us, Inc. is a professional tree service for the Chicago's North Shore, North and Northwest suburbs.  Tree trimming, tree removal, stump grinding, fertilizations, tree disease treatments and prevention as well as plant health care are just a few of our high quality, professional services.  Contact us today for a free analysis or quote at www.treesrusinc.com or at 847-913-9069.
Thanks for reading,
Nick

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