Photo of the Week

dwarf mistletoe on black spruce

Dwarf mistletoe causing witches' brooms on black spruce.

White pocket rot in wood

White pocket rot in pine. Some fungi selectively attack lignin leaving pockets of cellulose left behind in the wood.

class photo

Success growing 3 types of Pleurotus and fruiting occurred right on schedual for the forest fungi and wood decay lab session.


Heterobasidion root disease has recently been found in southeastern Minnesota. Be on the look out for this new invasive disease in Minnesota. Fruiting bodies are produced at the base of infected trees.

ambrosia beetle damage in wood

Ambrosia beetles carry stain fungi into wood that grow and are eaten by their larvae. The fungus is needed for them to mature. The stain fungi can produce interesting patterns in wood that are often used by artists. This vase was made by Alan Lacer from ambrosia beetle attacked maple.

sulphur shelf fungus

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

Oak with Brown Rot

Large losses in wood strength are associated with brown rot and this type of decay results in hazardous conditions in urban trees. Here a large limb has broken off this living tree that was decayed by the sulphur-shelf fungus.

Fusiform rust aecia

Aecia of Fusiform rust produced on young loblolly pine growing in Florida.

White pine blister rust aecia

Aecia of white pine blister rust on main stem of eastern white pine. Aecia are produced in late May to early June in Minnesota.

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.

Diplodia pycnidia

Pycnidia of Diplodia on a red pine cone

Canker on tree

An unusual looking perennial canker. What fungus do you think is the cause of this canker?

Anthracnose on maple

This homeowner asks "Is my maple tree going to die?" Anthracnose can cause lots of damage to leaves when we have a cool wet spring. It can look very bad but the tree is not going to die.

Anthracnose on oak

Anthracnose on oak can also cause great concern among homeowners.  Many jump to the conclusion that the tree is dying from oak wilt or some other serious disease.

spores of Penicillium

Many fungi such as this Penicillium species produce large quantities of asexual spores. Scanning electron micrograph of culture surface showing conidiophores and conidia.

Tree wrapped

To protect trees from winter injury, some arborists in China use elaborate methods of wrapping trees.

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. Watch this page for new photos each week.