Photo of the Week

Dwarf misletoe on black spruce

Witches' brooms on black spruce caused by dwarf mistletoe, Arceuthobium pusillum.

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.

Section of wood with soft rot

A cross section of wood showing wood cell walls that have been degraded by a soft rot fungus. Wood in extreme environemtns (such as very dry, very wet, high salts, etc.) can be attacked by soft-rotters. The fungus produces cavities inside the cell walls.

discoloration in maple due to ambrosia beetles

Ambrosia beetles tunnel into the xylem of trees bringing specific species of blue stain 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.

Fruiting bodies of Heterobasidion

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.

Sulfur shelf fungus fruiting

The sulfur shelf fungus (Laetiporus sulphureus), also known as "chicken of the woods" causes a brown rot. This fungus causes significant strentgh loss to wood and trees with fruiting bodies of this fungus have considerable decay. The fruiting bodies are an external indicator of a potential hazardous condition.

Tree fallen on house

Hazardous trees need to be removed before they fail! External indicators can be used to determine internal decay and the risk of a hazardous condition.

Silver splendor white pine

Patton's Silver Splendor White Pine, a selection we recently released at the University of Minnesota that has resitance to white pine blister rust. The tree has a silvery sheen due to increased wax on needle surfaces. The tree was originally selected many decades ago by Robert Patton and others at the University of Wisconsin. Screening and testing at the University of Minnesota has shown this selection to have excellent resistance. The original tree is from Duluth, Minnesota.

White pine blister rust aecia

Aecia of the introduced pathogen, white pine blister rust, showing the characterisitc "blisters" that are produced in the spring on white pine. Aeciospores infect Ribes.

DED Campus Before

The University of Minnesota St Paul Campus (1970's) before Dutch elm disease started to take its toll. This picture shows where the buses stop outside of the student center.

Canker on ash tree

An unusual looking canker on an ash tree found by a student who previously took this class. What canker causing fungus do you think is responsible?

Maple tree with anthracnose

This home owner asks "Is my tree going to die?" Maple anthracnose can cause problems in the spring and early summer. Will this tree die?

Anthracnose on oak

Spring infection of oak with oak anthracnose can mimic the symptoms of oak wilt. However, there are ways to differentiate oak wilt from oak anthracnose.

Tree wrapped with twine

Tree wrapped with heavy twine to prevent winter sunscald. This is a method used in China. Apparently it is effective but very labor intensive to put on and take off each year.

Leaves with salt damage

Maple leaves with a problem. How can you determine if this is caused by an abiotic or biotic agent?

red pine trees

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