Toads.—These are recommended as good insect traps to be used in mushroom houses, but I do not want them there; the cure is as bad as the disease. The mushroom bed is a little paradise for the toad. He gets upon it and burrows or elbows out a snug little hole for himself wherever he wishes, and many of them, too, and cares nothing about whether, in his efforts to make himself comfortable, he has heaved out the finest clumps of young mushrooms in the beds.
Fogging Off.—This is one of the commonest ailments peculiar to cultivated mushrooms. It consists in the softening, shriveling, and perishing of part of the young mushrooms, which also usually assume a brownish color. These withered mushrooms do not occur singly here and there over the face of the bed, but in patches; generally all or nearly all of the very small mushrooms in a clump will turn brown and soft, and there is no help for them; they never will recover their plumpness. Some writers attribute fogging off to unfavorable atmospheric conditions,—the temperature may be too cold, or too hot, or the atmosphere too moist, or too dry. I am convinced that fogging off is due to the destruction of the mycelium threads that supported these mushrooms; it is a disease of the "root," to use this expression; the "roots" having been killed, the tops must necessarily perish. If it were caused by unfavorable conditions above ground we should expect all of the crop to be more or less injuriously affected; but this does not occur; the mushrooms in one clump may be withered, and contiguous clumps perfectly healthy.
Anything that will kill the spawn or mycelium threads will cause fogging off to overtake every little mushroom that had been attached to these mycelium threads. Keeping the bed or part of it continuously wet or dry will cause fogging off, so will drip; watering with very cold water is also said to cause it, but this I have not found to be the case. Unfastening the ground by abruptly pulling up the large mushrooms will destroy many of the small mushrooms and pinheads attached to the same clump; and when large mushrooms push up through the soil and displace some of the earth, all the small mushrooms so displaced will probably waste away, as the threads of mycelium to which they were attached for support have been severed. A common reason of fogging off is caused by cutting off the mushrooms in gathering them and leaving the stumps in the ground; in a few days' time these stumps develop a white fluff or flecky substance, which seems to poison every thread of mycelium leading to it, and all the mushrooms, present and to come, that are attached to this arrested web of mycelium are affected by the poison of the decaying old mushroom stump, and fogg off. Any impure matter in the bed with which the mycelium comes in contact will destroy the spawn and fogg off the young mushrooms. Lachaume complains about the larvæ of two beetles, namely Aphodius fimetarius and Dermestes tessellatus, which "cause great damage by eating the spawn, thereby breaking up the reproductive filaments." Damage of this sort by these or any other insect vermin will cause fogging off. But I have not noticed either of the above beetles or their larvæ about our beds.
Flock.—This is the worst of all mushroom diseases and common wherever mushrooms are grown artificially. It is not a new disease; I have known it for twenty-five years, and it was as common then as it is now, and practical gardeners have always called it Flock. I say "worst of all diseases" because I know that mushrooms affected by it are both unwholesome and indigestible, and I can readily believe that in aggravated cases they are poisonous. It is caused by other fungi which infest the gills and frills of the mushrooms, and render them a hard, flocky mass; sometimes the affected mushrooms preserve their white skin, color, and normal form, at other times the cap becomes more or less distorted. The illustration, Fig. 26, is from life, and a good average of a flock-infested mushroom. In gathering mushrooms the growers should insist that every flock-infested mushroom be discarded, and consumers of mushrooms should familiarize themselves with this disease so as to know and reject every mushroom showing a trace of it.
Fig. 26. A Flock-Diseased Mushroom.
Flock does not affect all the mushrooms in a bed at any time, and I do not believe it spreads in the bed, or, to use the expression, becomes contagious. If one spot of mildew appears upon a cucumber, rose, or grape vine indoors, and is not checked, it soon becomes general all over the plant or plants, and if one spot of mold occurs in a propagating bed and is not checked at once it soon spreads over a large space and destroys every cutting or seedling within its reach, but this is not the case with flock in a mushroom bed. If one mushroom is affected with flock every mushroom produced from that piece of spawn is affected, but not one mushroom produced from the pieces of spawn inserted next to this one is affected by it; not even if the mycelium from the several lumps of spawn forms an interlacing web. If the flock is confined to the mushrooms produced from a certain bit of spawn some may ask, will the other pieces of spawn broken from the same brick produce flock-infested mushrooms? No. I have given this point particular attention, have kept the pieces of each brick close together, and where flock has appeared I have failed to find that the other pieces of spawn from that brick are more liable to produce flock-infested mushrooms than are the pieces of the bricks that, as yet, have not shown any sign of diseased produce.
How general is this disease? In a bed say three feet wide by thirty feet long and of two months' bearing one may get as few as five or as many as fifty flocky mushrooms; one or two may occur to-day, and we may not find another for a week or two, when we may get a whole clump of them, and so on. It is not the large number of them that makes them dangerous, for they never appear in quantity. They sometimes appear among the earliest mushrooms in the bed, but generally not until after the bed has been in bearing condition for a week or two.
What conditions are most favorable or unfavorable to the growth of this disease I do not know; but it is certainly not caused by debility in the mushroom itself, as the parasite attacks healthy, robust mushrooms and debilitated ones indiscriminately. This flocky condition is caused by one or more saprophytic and parasitic fungi of lowly origin, whose various parts are reduced to mere threads, simple or branched, and divided into tubular cells at intervals, or else they are long, continuous microscopic tubes without any partitions, except at those occasional points where a branch, destined to produce spores, is given off. Generally two or more species of these thread-fungi are present at the same time on the mushroom host, and by the multiplied crossing and interweaving of their threads and branches produce, through their great numbers, the whitish, felted mass of "flock"; while as individuals the threads are so minute as to be scarcely or not at all visible to the naked eye. Similar thread-fungi may often be found in the woods among damp leaves, under rotten logs, and on those porous fungi which project, shelf-like, from the trunks of trees. At present there is no way known for destroying the "flock," except to take up and destroy every clump of mushrooms attacked by it. Fortunately the disease is not very serious if proper precautions are observed; for, in our own cellars, where mushrooms have been grown year after year for the past eleven years, we get but few flocky mushrooms in any bed's bearing. The disease is not more common to-day than it was in any former year. But we give our cellars a thorough cleaning every summer.