Friends and Enemies of Mushrooms

Mushrooms are unable to get rid of a fly that has landed on them, a mosquito, an arachnid that has crawled onto them, a millipede, a pseudoscorpion or a slug that has stuck to them, let alone springtails and other tiny beetles, and so since the very beginning of their existence they have all been forced to live together.

This is attested by the distant past – fossils from the Jurassic and Cretaceous periods, in which paleomycologists discern the imprints of dipterans and other insects feeding on fungi, especially macromycetes. Today this phenomenon is not only obvious but also well explained. Protozoa, insects, other small animals and even some of the fungi's own kin (fungi) that feed on fungi or have found shelter in them, some even spending their whole life there, are called mycetobionts.

The way of life of fungi, especially the speed of formation and growth and the lifespan of the fruiting body, depends heavily on environmental conditions (the amount of warmth and moisture), and therefore some mycetobionts have also had to change their way of life and adapt by shortening their life cycle. First of all, those that are directly linked to the biological age of the fungal fruiting body. Incidentally, the mycetobionts, some more, some less, repay the fungi by dispersing their spores. For example, 200 species of dipteran insects alone maintain close ties with cap mushrooms – some feeding on them, others hiding from enemies in them, and still others spending one or another stage of development, or even their whole life, in the fruiting body.

The biological and physiological features of mycetobionts and their way of life have been studied reasonably well. Some insects can have several generations during the fungal growing season, others 2–3, and still others only one.

Some choose only the caps and lay their eggs only in them, from which voracious larvae develop; others choose only the stems; others both caps and stems; and there are also those that choose only the vegetative mycelium at the base of the stem (in the substrate).

One would think that the cep is attacked by 60 insect species, the slippery jack by 32, all the boletes by over 100, and the gilled mushrooms by 133 species of dipteran insects alone. Brittlegills alone are attacked by more than 30 species. Field mushrooms have far fewer "offenders" or "cohabitants" than brittlegills. Morels and false morels also have quite a few "offenders" or "tenants" – more than 50 species. Puffballs, bovists and other gasteromycetes, on the other hand, are disliked by insects; only the odd species visits them, feasting on their soft, rich trama without lingering long. The chanterelle is also disliked: only 3–4 species of "offenders" taste its trama, and even then, as if "afraid", they mostly bore only into the stem.

It has been established that some mycetobionts are content with some fungi, others with other fungi, while still others – the least choosy – do not distinguish between fungal species. For example, Mycetophila jungorum is aggressively disposed and attacks as many as 100 species of agaricoid fungi.

There are also those that have chosen only 1–2 fungal species. Lower mycetobiont activity has been observed at the beginning and end of the fungal growing season. There seems to be an inverse relationship between the mushroom crop and the activity and intensity of the mycetobionts. The larger the mushroom crop, the less they are attacked (get maggoty), although this is not confirmed every year.

It is supposed that fungi release certain attractant substances that help female mycetobionts find their way in the depths of the forest, and even lure them to find a suitable mushroom in which to lay their eggs, while at the same time carrying away that mushroom's spores and extending its range. It is an interesting phenomenon, it is being studied, and it has good prospects for the future in protecting ceps and other valuable mushrooms from an excessive horde of "offenders", which sometimes destroy as much as about 60–70 percent of the crop not only of ceps but of other mushrooms too. However, this is responsible and rather complex work, requiring prior clarification of the biology of the harmful insects, their biotope attachment, seasonal activity, their relationships with other mycetobionts, and their significance in the life of the forest and in the biogeocoenosis. Sometimes, by breaking one vital link in a biocoenosis, one can bring about even more undesirable phenomena.

Among the mycetobionts there are also good-for-nothings from among the fungi's own kin – mostly ascomycetes of the genus Hypomyces. When warm and humid weather persists, favourable conditions arise for these fungi to carry out their wicked designs. You will often come across a leaning birch bolete, deformed green, red-stemmed or brown-capped Xerocomus boletes, the grey rollrim, some brittlegills, not infrequently a cep, a slippery jack or even a chanterelle, and other mushrooms.

The favourite underside of the cap (gills, tubes) becomes covered with a film of white, yellow or pinkish parasitic mould, and not infrequently the attacked mushroom looks as if it had turned horny. Affected mushrooms are unfit for food and are sometimes even poisonous. The most widespread ascomycete is Apiocrea chrysosperma (Tul.) Syd., and in its conidial stage Sepedonium chrysospermum (Bull.) Fr. Although this lurker does the most damage to mushrooms, it looks gentler than the parasitic bolete (Xerocmusparasiticus (Bull.: Fr.) Quel.), which parasitises the common earthball (Scleroderma au-rantium Pers). Who would think that a mushroom of bolete origin, and an edible one at that, destroys a poisonous gasteromycete by settling on its root base. It is very rare, found only once (Anykščiai district). Or the powdery piggyback (Asterophora lycoperdoides (Bull.) Ditm.), but this one, as a saprotroph, has linked its life mostly only with dead brittlegills, especially the blackening brittlegill and the fading brittlegill. I once observed how the piggyback had "occupied" more than 60 fruiting bodies of the fading brittlegill in one entire compartment of bilberry pine forest in the Daunoriai forest district of Aukštaitija National Park. There are also more cannibal fungi that are fond of their living and dead kin.

Incidentally, roe deer, elk, wild boar, squirrels, voles, jays, thrushes and some other forest dwellers sometimes feast on mushrooms out of curiosity, sometimes to satisfy their hunger, and sometimes when they are unwell. Squirrels eat the most mushrooms.

Research on mycetobionts has been carried out only quite recently; it began only in the 1970s (in Germany, Finland, Hungary, England and Russia). It is gratifying that in recent years it has also been carried out in Lithuania (Institute of Ecology).