Witches Broom

Most trees can show signs of witches broom. Witches broom is easily identified as an abnormal dense cluster of twigs growing from a central source, many upright or spreading and is easiest to see when there are no leaves on the trees.

Witches' brooms are symptoms of stresses, both biological and environmental, such as infection that is formed on plants as a result of attack by parasites.

The parasites whose presence stimulates the formation of witches brooms include fungi such as Taphrina tugida (on alder, birch, red cedar, and white cedar); phytoplasmas (bacterial-like organisms) and bacteria (on pine); dwarf mistletoes (on pine, larch, and fir); viruses (on peach and black locust); and mites (on hackberry and willow). Organisms such as aphids, nematodes, and mistletoe plants can cause abnormal growth when they attack a host tree. Environmental stresses that injure the

growing points of branches can also trigger the formation of brooms. Some brooms appear to be caused by genetic mutations in the buds of the branches. Unlike brooms caused by living organisms, there is usually just one broom per tree when the cause is a genetic mutation. The stimulus responsible for certain types of witches' brooms is not well understood.

Knowing the type of host plant can help determine the cause of the witches broom. Pinpointing the cause of a witches' broom can be difficult, especially if the formation is related to an environmental factor. Analyzing the plant tissue for infectious agents such as phytoplasmas requires specialized testing that can be costly.

Although they can occur on nonwoody plants such as alfalfa, potato, and aster, they are most familiar on shrubs and trees, where some may exceed 10 feet in diameter. In others, they are small and well-hidden.

They may resemble a bush, a bird's nest, or a handleless broom attached to the host plant. Some may consist wholly or partially of dead branches; others, of living branches that can continue to grow for many years. The leaves they bear may be distorted; they may appear later in spring and drop earlier in fall than the normal leaves of the plant, and they may be yellowed. Flowers are rarely produced. The witches broom may last several years. Although some people consider witches broom unsightly, serious injury seldom results.

Some witches' brooms may cause stunting or even death of the host plant, especially when many brooms develop on one individual. Other kinds do not appear to damage the host appreciably; however, they are unsightly and therefore may be objectionable, especially on street and ornamental trees. Control of witches' brooms on woody plants is best accomplished by removing and burning the brooms.

In medieval times, mysterious and unexplainable occurrences were often blamed on witchcraft. Brooms during this time were made of bundles of twigs. The term witches' broom comes from the German word Hexenbesen, which means to bewitch (hex) a bundle of twigs (besom).

Piptoporus betulinus

Brown Cubical Rot of Birch

(Piptoporus betulinus)

Phylum: Basidiomycota

Order: Polyporaceae

Family: Fomitopsidaceae

Scientific name: Piptoporus betulinus (Bull.: Fr.) Karst

Common names: Birch polypore.

Derivation of name:

Piptoporus means "a polypore that falls off"; betulinus means "inhabiting birch trees."

Piptoporus betulinus is restricted to birch as a host. This fungus is found throughout the range of birch. Saprobic and possibly parasitic; growing alone or gregariously on dead birch trees, logs, and occasionally on living trees; found year-round; occurring wherever birch trees occur naturally. Piptoporus betulinus causes a yellowish to brown cubical rot, and is a powerful decomposer of dead wood. Whether

or not it attacks living trees as a parasite is contended.

Identification: The fruiting bodies are annual, leathery, with a short, stout stipe, and a cap from 5 up to 15 cm deep, x 25 cm wide x 6 cm high. Kidney-shaped in outline, broadly convex to more or less flat; growing shelf-like or hoof-like, dry with a smooth or somewhat roughened "skin" that often peels away. The upper surface is smooth and glabrous when young, whitish to pale brown with darker brown streaks, becoming darker brown and scaly, with a margin that extends below the pore surface. Stipes (if present) are lateral, thick and up to 6 cm long. The pore surface is white, becoming light brown and slightly tooth-like with age, pores circular, 3-5 per mm. Tubes to 1 cm long. Context white, easily separating from tube layer when fresh.

Stem: Absent or rudimentary and stubby.

Flesh: White; thick; corky.

Taste: Slightly bitter; odour strong and pleasant.

Spore Print: White.

Microscopic Features: Spores: 3-6 x 1.5-2 µ; smooth; cylindrical to long-elliptical. Cystidia absent.

Microscopic Characteristics:

Hyphae in the context of the fruiting body of two types: thin-walled, hyaline with clamp connections, and thick-walled, aseptate Basidiospores cylindric, allantoid, hyaline, smooth, IKI-, 5-6 x 1.5-1.7 µm. Growth in culture moderately rapid, mat colourless to white, forming compact balls of mycelium on surface of medium, chlamydospore-like swellings, laccase negative.

Piptoporus betulinus is often present in dead branches of dying trees. After trees die, rot develops in the bark and sapwood, and generally spreads to the centre of the trunk. Infected wood decays rapidly; laboratory studies have shown reduction of wood density of 30-70% in four months. Decayed wood is yellowish-brown and cracks into cubes with thin white mycelial mats forming in the cracks. Wood in advanced stages of decay is very light in weight and easily crumbles to powder. Piptoporus betulinus is one of the few brown rotting fungi that only attacks hardwoods. Although it is restricted to birch hosts in nature, other tree species such as pine, spruce, and poplar have been successfully inoculated in lab and field experiments.

Anyone who has spent time in birch woods has seen Piptoporus betulinus on dead birch trees and logs, or occasionally on living trees. The species is an attractive polypore, easily recognized by its habitat on birch wood and the fact that the cap folds over to make a distinctive, smooth rim around the pore surface. The caps are whitish to brownish, and the pore surface is whitish or grayish brown. Although Piptoporus betulinus is annual and does not actually live for more than one season, its fruiting bodies are somewhat tough and are sometimes found in the next year (usually somewhat blackened).

Piptoporus betulinus is apparently edible when young, but it is quite a tough and corky mushroom. However, the fungus does have antibiotic and styptic properties and the Tyrolean Ice Man was carrying it around for some reason.

Sometimes referred to as Razor strop fungus which reflects the use in Victorian times of this fungus to sharpen cut-throat razors in the absence of leather strops.

Tar spot

Tar Spot (Rhytisma acerinum)

Common Name: Tar Spot

Scientific Name: Rhytisma acerinum

Type: Fungus

Principle Host Trees & Shrubs:

Sycamore and other Maples (Acer species).

The fungus overwinters on fallen leaves. Fresh

needle-shaped spores are produced in Spring

which have a sticky coating and are spread by

the wind. The spores attach themselves to the

new leaves as they form. Once on the leaves, the

spores germinate and penetrate through the

stoma. The subsequent infection causes chlorosis

(absence of chlorophyll) of the leaves in localized

yellow spots. As it matures, a raised, shiny black

spot appears on the infected leaves. Can cause

premature leaf drop but the vigour of the tree is

rarely affected. Rarer in cities due probably to

fewer fallen leaves left under trees.

Control is generally unnecessary. If a problem on ornamental species dispose of fallen leaves in Autumn to reduce spore levels in Spring.

Tar spot is a fungal disease that doesn't require a fancy microscope for

diagnosis. As you might guess, the disease is characterized by raised,

black spots on leaves. Tar spot is caused by the fungus Rhytisma

acerinum. The tar-like spot is a fruiting structure of the fungus that

survives the winter on fallen leaves. In the spring, mature spores of the

fungus are released and blown by wind to newly emerging leaves.

Early infections appear as yellowish spots on the upper leaf surface. Later

in the summer, black tar-like spots form and may be one-half inch in

diameter. These black spots have a ridged appearance if examined

closely. The undersides of the leaves appear cupped directly beneath the

tar spots.

Fortunately, tar spot does not cause serious harm to established trees.

Some early leaf drop may occur. Raking and removing fallen leaves can

help to destroy overwintering fungal inoculum. Although fungicides can

be applied in the spring to protect newly emerging leaves, their use is

seldom warranted.

What it does tell us however, due to the fact that the Sycamore is capable of standing higher levels of pollution than many other trees, whereas the Tar Spot fungus needs cleaner air, and does not do well in polluted areas, this fungus is particularly sensitive to sulphur dioxide air pollution. Trees growing near to industrial centres with high levels of sulphur emissions do not show any sign of these leaf-blackening fungi. It gives a highly visible view of the air pollution in the area.

There are a number of genetically-distinct ‘races’ of the fungus, which vary in the species of Acer that they affect.

Feeding and other inter-species relationships

Rhytisma acerinum is associated with:

Field Maple (Aceraceae) apothecium is saprobic on rotting leaf Ellis, M.B. & J.P., 1997
Sycamore, Great Maple (Aceraceae) apothecium is saprobic on rotting leaf Ellis, M.B. & J.P., 1997
Field Maple (Aceraceae) stroma parasitises living leaf Ellis, M.B. & J.P., 1997
Sycamore, Great Maple (Aceraceae) stroma parasitises living leaf Ellis, M.B. & J.P., 1997

Associated with Rhytisma acerinum:

stroma is associate of apothecium Lachnum rhytismatis - a discomycete (Helotiales: Hyaloscyphaceae) Ellis, M.B. & J.P., 1997

Jews Ear Fungus

Jew's Ear (Himeola auricula)

'Jew's ears,' a large fungus often to be found on the Elder (Sambucus nigra), the name a corruption of 'Judas's ear,' from the tradition, that Judas hanged himself on the Elder. It is of a purplish tint, resembling in shape and softness the human ear, and though it occurs also on the Elm, it grows almost exclusively on Elder trunks in damp, shady places. It is curious that on account of this connexion with Judas, the fungus should have (as Sir Thomas Browne says) 'become a famous medicine in quinses, sore-throats, and strangulation ever since.' Gerard says, 'the jelly of the Elder otherwise called Jew's ear, taketh away inflammations of the mouth and throat if they be washed therewith and doth in like manner help the uvula,' and Salmon, writing in the early part of the eighteenth century, recommends an oil of Jew's ears for throat affections. The fungus is edible and allied species are eaten in China.