Photo of the Week

dwarf mistletoe on black spruce

Dwarf mistletoe, Arcuethobium pusillum, is a parasitic plant that attacks black spruce causing large witches' brooms

Heterobasidion root rot

Fruiting bodies of Heterobasidion irregulare at the base of a red pine. Heterobasidion causes a serious root rot in pines and has recently been found in southwestern Minnesota for the first time. Be on the look out for this new disease in Minnesota and report all new findings.

White pocket rot in wood

A split open conifer log showing a white pocket type of wood decay. Fungi causing this decay have the ability to remove large amounts of lignin but leave cellulose. The white pockets are areas of delignified wood. These fungi are of great interest for their potential in bioprocessing applications where lignin removal is needed such as biofuel production, biopulping, biobleaching of pulps, etc.

discoloration in maple due to ambrosia beetles

Ambrosia beetles tunnel into the xylem of trees bringing specific species of blue stain fungi with them. The larvae of the ambrosia beetles feed on the fungus. Streaks of discoloration associated with the beetle galleries can be seen in this turned maple bowl resulting in a strikingly beautiful piece of art. Made by artist and wood turner Alan Lacer.

Oak with Brown Rot

Branch failure in an oak tree caused the brown rot fungus Laetiporus sulphureus.

Decay fungus on oak

The sulphur shelf fungus, Laetiporus sulphureus, fruiting on a living oak. This fungus causes a brown rot in trees and a loss of wood strength properties early in the decay process.

Fusiform rust aecia

Aecia of fusiform rust on the main stem of young slash pine in northern Florida. Aeciospores infect red oak leaves in spring (February/ March).

White pine blister rust aecia

Aecia of white pine blister rust form on the edges of the infected area in spring (late May / early June in Minnesota). Aeciospores infect Ribes.

Brown spot

Brown spot caused by Mycosphaerella dearnessii (Lecanosticta acicola) on longleaf pine

Oak wilt mats

Oak wilt mat produced on a red oak under the bark. In spring, the pressure pads break open the bark and the aromatic fungus attracts Nitidulid beetles. 

DED Campus BeforeDED Campus After

The University of Minnesota Saint Paul campus looking toward the student center from Cleveland Ave before (left) and after (right) large losses of elms from Dutch elm disease.

Canker on tree

What type of canker do you think is on this ash tree?

Maple anthracnose

This homeowner is very worried about his tree. He asks "Will my maple tree die?" This is maple anthracnose and while leaves can be severely affected when we have a wet spring - the tree will not die.

Anthracnose on oak

Oak anthracnose is a leaf disease but can mimic the symptoms of oak wilt.

Tree wrapped for winter sunscald in China

To protect thin barked trees planted in China from winter sunscald trees are carefully wrapped with thick twine.

SO2 damage on birch leaf

Some symptoms of air pollution can be very distinctive such as this damage on birch due to SO2

red pine trees

Keeping forest and urban landscape trees healthy requires a good knowledge of tree diseases. This class will provide you with important information you can use in the future.