Red stain in box elder is bright red when fresh. The color is from compounds produced by the tree as a defense against invading fungi. Norman Borlaug, who was awarded the Presidential Medal of Freedom, Congressional Gold Medal AND the 1970 Noble Peace Prize, did research on red stain in box elder for his MS degree at the University of Minnesota and wrote his thesis on this topic. His awards did not come from this work but from his work on wheat rust and producing new varieties that helped to feed billions of people.
A leafy mistletoe on juniper in Northern Arizona. In desert regions, the leaves on the mistletoe can be reduced to just green stems.
Dwarf mistletoe in the western United States (this one is on ponderosa pine - Arceuthobium vaginatum) can be large in comparison to the small shoots of dwarf mistletoe on spruce here in Minnesota.
Witches brooms on black spruce in northern Minnesota with dwarf mistletoe infection caused by Arceuthobium pusillum.
Galls and burls on trees can have very dense wood and interesting patterns as you can see in this bowl made from a gall on an oak tree.
Large gall on a cottonwood by Minnehaha Falls in Minneapolis.
Some fungi have fruiting bodies that glow in the dark and some others have mycelium that is bioluminescent such as Armillaria. If you remove the bark of a tree with active Armillaria mycelium, the white mycelial fans glow brilliantly.
Armillaria fruiting at the base of a tree. Fruiting bodies in Minnesota usually appear in September.
Heterobasidion irregulare fruiting bodies at base of a red pine. This pathogen has been found in southeastern Minnesota and is expected to spread. The Wisconsin DNR reports 31 counties in Wisconsin with Heterobasidion Root Disease. Be on the look out for this pathogen in Minnesota.
A pine board with white pocket rot. These interesting white rot fungi have the ability to selectively degrade lignin leaving cellulose behind. Some fungi, such as Porodaedalea (Phellinus) pini, produce small spindle-shaped white pockets while some other white pocket rot fungi produce much larger zones of delignification.
Blue stain is moved around by bark beetles and other insects. The "blue" color is due to the pigment inside the hyphae. Although the stain disfigures wood, new used are being found for its use.
Zone lines or pseudosclerotial plates are made up of fungal melanin that acts to separate incompatible white rot fungi from each other. Often called spalted wood, it is used by woodworkers and artists to make interesting objects.
As you eat the Pleurotus mushrooms you grew, remember meiosis has occurred in the basidia and those gills are filled with hundreds of thousands of extraordinary basidiospores.
Aecia on the bottom surface of a hawthorn leaf caused by Cedar-Hawthorn Rust, Gymnosporangium globosum.
Juniper broom rust with telia coming out of the branches. The telia produce basidiospores that infect serviceberry (Amelanchier)
Fusiform rust with pycnia oozing pycniospores. This sweet liquid attracts insects that move the pycniospores from one pycnium (+) to another of an opposite mating type (-).
Aecia of white pine blister rust on an infected white pine. The aecial stage is only seen in a 1-2 week period around the beginning of June. This spore stage gives the disease its name "blister rust".
Lophodermium has long, thread-like ascospores with a sticky sheath that helps adhere them to needles after they are ejected out of the hysterothecium.
Lophodermium on old pines needles showing black hysterothecia. These black fruiting bodies open producing ascospores from the compressed apothecium that is under the black stromatic material.
The Synnemata of Ophiostoma novo-ulmi with spores masses of asexual spores can be beautiful but this fungus packs a powerful punch and is responsible for killing hundreds of millions of elm trees in the United States.
A red oak infected with oak wilt the previous year will produce oak wilt mats under the bark the following year. In spring, the pressure pads break open the bark and the aromatic fungus attracts Nitidulid beetles. The photo shows the pressure pads of the fungal mat when the bark was pulled off. These mats would be full with conidia and if both mating types are present, perithecia will also form.
Chestnut blight has killed millions of American chestnut trees and finding chestnut trees and wood is very difficult. However, at times, a few larger pieces of wood can be found and used to make interesting items, like the bird above.
Cankers on trees can sometimes look unusual. What fungus do you think caused this canker on black ash?
This homeowner was very upset and kept saying, "Will my maple tree die? Do I need to cut the tree down?" What would you say to him? See close up photo of infected leaves below.
Infected maple leaves observed in late May.
One BIG mushroom and the gills will be filled with basidia and basidiospores. See photo below.
A section of a gill showing basidia with 4 basidiospores on each basidium.
Stem girdling roots, formed from planting trees to deep or from twisted roots grown in pots when the trees were young, can kill trees as they get older.
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.