About Shot Gun Fungus

The Dark Brown Waxy Spots
In the last 3-4 years, hardly any of these years have passed without us getting a letter, a telephone call from an individual telling us about a problem they are having with some waxy substance sticking all over the side of a building or house.

These spots appear to stick to most any surface and are extremely difficult to brush off. We have heard of court cases  where people have tried to blame the spots on industrial plants or beekeepers in the area. Some have thought the spots were pollutants of the factories or bee feces.
An interesting observation has been that the spots seem to appear in the spring and fall of the year rather than the mid-summer. Also, they have been found up as high as the second story of a building and seem to be more on the southwest side of buildings. However, this has not always been the case.

The spots are about 1-2 millimeters in diameter and somewhat raised or globular in appearance. The outer coating is dark brown and darken with age. The inside is off-white and appears to be granular but gummy and thick.

The Identity of the Brown Waxy Spots
The spots that we have been ta1king about are not environmental pollutants,insect dung,fly specks or scale insects, but have been identified as masses of mature spores that have been expelled or shot from fruiting bodies of fungus identified as SPHAEROBOLUS STELLATUS TODE. A relative of the birds' nest fungus, it is commonly called artillery or shot gun fungus by fungi specialists.

How the Shot Gun Fungus Develops
The fruiting body develops in hardwood mulches and is approximately 2 millimeters in diameter. It produces spores inside the body. When the fruiting body is mature, it splits radially from the apex, forming 4-8 teeth along the outer rim of the now cup-like structure.
The round mass of spores, known as the glebal mass or peridiole, is about one millimeter in diameter and rests in liquid at the bottom of the cup of fruiting body.

Soon the tissue layers in the fruiting body separate and are attached only at the teeth. About 5 hours after opening, the inner cup is violently blasted out just like a shotgun blast. The glebal mass is catapulted into the air.
They say that the SPHAEROBOLUS firing mechanism generates about 1/10,000 horse power and can throw the glebal up some 7-8 feet. On a windy day,these masses can be picked up to 15 feet or more as evidence by the fact that they have been found up that high on some buildings.
When the sticky glebal mass hits a solid surface, it Sticks. The fruiting body is strongly phototropic and the glebal mass is shot toward the brightest light source.

Outdoors the masses will be directed at the sun or a highly reflective surface such as glass windows and light- colored walls or automobiles in a parking lot.

What the Shot Gun Fungus Develops on
The shot gun fungus grows on dung and well-rotted wood such as wood chips used to mulch flower beds and areas around buildings. This is probably the key to our problem. All cases where the fungus has been reported has always been close to where hardwood chips have been used as a mulch.
The fruiting body cannot mature without proper light and the optimum temperature for the production of the glebal masses is about 10-20 degree centigrade. At temperatures above 25 degree centigrade, activity ceases and no fruiting bodies are produced. Therefore, cool moist conditions are needed and this is why all those reports show up in the spring and fall rather than mid-summer.

Some Suggestions on how to Lesson the Fungus
Little work has been done on fungicide application to control this fungus. Since the problem exists where hardwood mulches have been allowed to decay, this is probably the area to concentrate on. Using some other type of mulch might be helpful or, at least put several inches of new fresh mulch on top of the decaying stuff. Be careful about scraping the glebal masses off a wall, because if they fall to the ground, up they come again.

Well, at least you know what it is and it's not from outer space, a factory chimney or some untidy bug.