INSECT AND OTHER ENEMIES.

The mushroom grower has his full share of insects to contend with, and in order to overcome them one should acquaint himself with them, and know what they are, what they do, whence they came, and how to destroy them. One should study the diseases and mishaps of his crop and endeavor to know their cause. If we know the cause of failing health in plants, even in mushrooms, we can probably stop or devise a remedy for the disease or means to prevent its recurrence, and if we can not benefit the present subject we are forewarned against future attacks. But there is a deal of mysterious trouble in this direction in mushroom-growing. We are likely to know something about the depredations committed by insects or parasitic molds above ground, but I am sure there is a good deal of mischief going on under ground of which we know very little, if anything. The ills to which the mycelium is subject are not at all fully understood.

"Maggots."—This is the common name among practical mushroom growers for the larvÆ of a species of fly (Diptera) which from April on through the warm summer months renders mushroom-growing unprofitable. It is unavoidable, and so far has proved invincible. It attacks the mushrooms in deep cellars, above-ground houses, greenhouses, or frames, and is often quite common in early appearing crops in the open fields. We sometimes read that it does not occur in unheated cellars, but this is a mistake, for in our unheated tunnel cellars, where the temperature in April does not exceed 55°, maggots always appear about the end of this month. But it is true that in the case of cool houses and where the beds are covered over with hay or straw maggots do not appear as early in the season as they do in warm houses and open beds. While rigid cleanliness, and care in keeping the house or cellar closed, no doubt have much to do in lessening the trouble, I have never been able to overcome it, and know of no one who has. We simply stop growing mushrooms in summer.

The maggots or larvÆ are about three-sixteenths to four-sixteenths of an inch long, white with black head, and appear in all parts of the mushroom, but mostly in the cap and at the base of the stem, and perforate hither and thither leaving behind them a disgusting network of burrows. The tiny buttons, about as soon as they appear at the surface of the ground, are infested, but this does not check their growth, and when they become mushrooms large enough for gathering, unless it be for a dark looking puncture or tracing now and then visible on the outside of the caps and stems, there are but few signs to indicate to the inexperienced eye the presence of maggots. And this is why maggoty mushrooms are so often found exposed for sale in summer. But in large or full-grown mushrooms, and especially the white-skinned varieties, their presence is visible enough. Although very repugnant, however, and utterly unfit for food, maggoty mushrooms are not poisonous.

But all the mushrooms of summer crops are not maggoty, only a large proportion of them; the evil begins in April, and increases as the summer advances, until August, when it decreases, and in October completely stops—at least this is my experience.

A solution of salt, saltpeter, or ammonia sprinkled over the surface of the beds does not, in this case, do any good as an insecticide, pyrethrum powder diffused through the atmosphere, and tobacco smoke, have been ineffectual. Burning a lamp set in a basin of water with a little kerosene floating on the surface is a most doubtful operation. Multitudes of flies are destroyed by this lamp trap, but they are the poor little innocent "manure flies," and the atmosphere of the house is vitiated and rendered unhealthy for the crop. I have tried these lamp traps season after season, and never knew of their doing any good; that is, the maggots seemed just as numerous in the lamp-trapped cellar as in the other cellar in which no lamp trap had been used.

Regarding this "maggots" question, Mr. J. F. Barter, of London, writes me: "During the summer months the outdoor mushrooms get maggoty before they are big enough to gather, but of course they can be grown in cool cellars all the year round.... I know of no sure cure for them (the maggots); of course a slight sprinkling of salt with manure or mold does prevent, to a certain extent, but it must be used very carefully." Now my experience is, as I have already said, that it is impossible to grow mushrooms here in summer, even in cool cellars, without having them more or less maggoty. As regards the salt and loam preventive, I have tried it lightly and heavily, but without any apparent good effect.

Black Spot.—All mushroom growers are familiar with this disease, but unless it appears in pronounced form very little notice is taken of it, even by market men, for we see spotted mushrooms continually exposed for sale. It appears as dark brown spots, streaks, or freckles, on the top of the mushroom caps, and increases in distinctness and breadth with age. Fig. 25. It is caused by eel worms (AnguillulÆ). These minute creatures enter the mushrooms when the latter are in their tiniest pin form and before they emerge from the ground. If a button arises clean it remains clean, if diseased it continues to be diseased, and it is a fact that if one mushroom in a clump has black spot we usually find that every mushroom in the clump has it. But mushrooms growing from the same bit of spawn and that come up an inch or two away from the spotted ones may be perfectly clean. Black spot has never occurred with me in new beds, and seldom in those in vigorous bearing, but it generally appears in beds that have been in bearing condition for some weeks or are declining. It does not confine itself to any particular spot or part of the bed, and sometimes it is much more plentiful than at others. Between October and March we have very little black spot, but as the spring opens this disease increases. During the winter season, with careful attention, perhaps not so much as one per cent will show black spot, but as the warm weather sets in the per centage increases until in May, when as many as twenty per cent may be affected by it.

Black spot is a disease, however, that can be controlled. Keep everything in and about the mushroom houses rigidly clean, and as soon as a bed has ceased to bear a crop worth picking clear it out, lime-wash the place it occupied, and make up another bed. Carefully observe that no old loam or manure is allowed to accumulate anywhere, or green scum forms upon the boards, paths, or walls; boiling water impregnated with alum poured over the boards, walls, and other scum-covered surfaces, will kill the eel worms, but it should not be allowed to touch the mushroom beds that are in bearing or coming into bearing. Much can be done to protect the bearing beds from the ravages of this pest: In gathering the mushrooms remove every vestige of old stump and fogged-off mushrooms, keep the holes filled up with fresh loam, and when the bed has been in bearing condition for a fortnight sprinkle it over with a solution of salt, and next day topdress with a half-inch coating of finely sifted fresh loam; firm it to the bed with the back of the hand, for it can not be pressed on with a spade on account of the growing mushrooms.

Is black spot unwholesome? I do not think so. I have never known any ill effects from eating it. The spotted parts are merely flavorless and tasteless. But it is a very disgusting disease, and no one, I am sure, would care to eat eel worms with their mushrooms. Until quite recently I used to regard the black spot as the mark of some parasitic fungus, and, acting under this impression, sent affected mushrooms to Dr. W. G. Farlow, Prof. of Cryptogamic Botany at Harvard University, for his opinion. He wrote me: "I find that the trouble is due to AnguillulÆ, and I find an abundance of these animals in the brown spots." He advised me to submit them to an expert in "worms." I then sent samples to my kind friend, Mr. William Saunders, of Washington, D. C., who submitted them, for me, to Dr. Thomas Taylor, the microscopist to the U. S. Department of Agriculture, and who replied: "I recommend that you use a sprinkling of scalding water thoroughly over the entire surface of the bed, especially the portion next to the boxing. The scalding water should be applied before the buttons appear, but not penetrate more than one-eighth of an inch below the surface. AnguillulÆ abound wherever decaying vegetable matter exists.... The green algÆ on the outside of flower pots abounds in the anguillulÆ."

Manure Flies.—This is the name we give to the little flies (a species of Sciara) that appear in large numbers in spring and summer in our mushroom houses, or, indeed, in hotbeds or structures of any sort where manure is used, as well as about the manure heaps in the yard. On account of their habits they are regarded with much ill-favor. They hop about the house and are continually running over the mushrooms, beds, and walls, in the most suspicious manner. But, notwithstanding this, I am inclined to regard them as perfectly harmless so far as injuring the mushroom crop is concerned, except the fact that they soil the mushrooms somewhat by their traveling over them with their muddy feet.

In attempting to get rid of the maggot fly I have destroyed large numbers of these little innocents, but without any apparent diminution in their numbers. Lachaume recommends: "These flies may be destroyed by placing about a number of pans filled with water to which a few drops of oil of turpentine have been added. The flies are attracted by the odor and drown themselves. They may also be caught with a floating light, in which they will burn their wings and fall into the water." I have found that pure buhach powder dusted into the air or burned on a hot shovel in the mushroom house has been more effective in destroying these flies than either the lamp or drowning process.

Slugs.—These are serious pests in the mushroom house, especially in above-ground structures, and they also occur in annoying numbers in cellars. Wherever hay or straw is used in covering the beds, or there is much woodwork about the house, slugs appear to be most numerous. They are very fond of mushrooms and attack them in all stages, from the tiny button just emerging from the ground to the fully developed plant. In the case of the buttons or small mushrooms they usually eat out a piece on the top or side of the cap, and as the mushroom advances in growth these wounds spread open and display an ugly scar or disfigurement. They also bite into the stems. But in the case of fresh, full grown mushrooms they seem to have a particular liking for the gills, and eat patches out of them here and there.

"Bullet" or "Shot" Holes.—My attention was first called to these by Mr. A. H. Withington, of New Jersey. They are little holes cut clear through the mushroom caps, as if perforated by a buckshot, and are evidently the work of some insect. He had, before then, submitted some of these perforated mushrooms to Prof. S. Lockwood, who sent them to Prof. C. V. Riley for his opinion. Prof. Riley replied that: "It is quite likely that the damage was done by some myriapod, possibly a Julus, or some of its allies. Only observation on the spot will determine this point." As I never had any trouble with myriapods attacking mushrooms and had seen nothing of this "bullet hole" work in our own beds I was much interested in the question and determined to look out for it, so I marked off a part of a bed and left that uncared for. I soon found out the trouble. These holes are the work of slugs which I have found and watched in the act of eating out the holes. To find the slugs at work, one has to take his lantern and go out and look for them at night. And to find out about plant parasites—be they fungus, or insect—one has to let them alone and watch them. Had we kept up our unsparing hunt for slugs, probably we should not yet have known what caused these "bullet holes," for no slug would have been left alive long enough to eat a hole through a mushroom cap.

Slugs must be caught and killed. We can find them at night by hunting for them by lamp-light; their slimy track glistens and reveals their presence. A few small bits of slate or half rotten boards with a pinch of bran on them laid here and there about the beds are handy traps; the slugs gather to eat the bran, hide beneath the rotten wood, and can then be caught and killed. Fresh lettuce leaves make a capital trap, but lettuces in January or February are about as scarce as mushrooms themselves. A dressing of salt is distasteful to slugs, and not injurious to mushrooms. Strong, fresh lime water may be freely sprinkled over woodwork, pathways, walls, or elsewhere where slugs might gather and hide themselves; but this solution should not be used upon the mushroom beds. Rigid cleanliness, however, about the mushroom house, and an ever-alert eye for slugs, should keep them under.

Wood Lice.—These are sure to be more or less abundant in every mushroom house, even in the cellars. They crawl in through doors, ventilators, or other interstices, and are brought in with the manure, and find shelter about the woodwork, manure, or any bits of dry litter that may be around. They attack the pinhead and small button mushrooms by biting out little patches in their tops and sides; and although these patches are small to begin with, the blemish spreads as the mushroom grows, and is an objectionable feature. Trapping and killing the insects is the chief remedy. Put part of a half boiled potato (for which no salt had been used) into a little pasteboard box, and cover the potato with some very dry swamp moss, lay the box on its side, and open at the end on the bed. The wood lice will gather to eat the potato, and remain after feasting because the dry moss affords them a cozy hiding place. Several of these little boxes can be used. Go through the house in the morning, lift the little traps quickly, and shake out any wood lice that may be in them into a tin pail (an old lard pail will do), which should contain a little water and kerosene. These traps may be used for any length of time, merely observing to change the potato now and again to have it in appetizing condition. Hot water or strong kerosene emulsion may be poured about the woodwork, walls, and pathways, to destroy the wood lice, but should not be allowed to touch the beds. Poisoned sweet apples, potatoes, and parsnips have been recommended as baits for these pests, but I must discourage using poisons of any sort in the mushroom house. Six or eight inch square pieces of half rotten very dry boards laid in pairs, one above the other, also make capital traps; the wood lice gather there to hide themselves; these traps should be examined frequently and the insects shaken into the pail containing water and kerosene.

Mites.—Two kinds of mites are very common about mushrooms in spring and summer; one is whitish and smaller than a "red spider" (one of the commonest insect pests among garden plants), and the other is yellowish and as large as or larger than a "red spider." But I do not think that either of these mites is worth considering as a mushroom pest. The yellow mite (probably Lyroglyphus infestans) is extremely common in strawy litter on the surface of hotbeds, and I have no doubt finds its way into the mushroom house as manure vermin rather than a mushroom parasite. They are the effect and not the cause of injury to the crop. When mushrooms are wounded or cracked, particularly about the stem, the crevices often become abundantly inhabited with these mites, but they do no material damage.

Mice and Rats.—These rodents are very fond of mushrooms, and where they have access to the beds are troublesome and destructive. Both the common house mouse and the white-bellied fence mouse are mushroom destroyers, but, so far, the nimble but timid field mouse (among garden, open air, and frame crops generally) has never yet troubled our mushrooms, but I can not believe that this immunity is voluntary on its part. The mice bite a little piece here and there out of the caps of the young mushrooms, and these bite-marks, as the mushrooms advance in growth, spread open and become unsightly disfigurements. In the case of open mushrooms, however, the mice, like slugs, prefer the gills to the fleshy caps. Rats are far more destructive than mice. Trapping is the only remedy I use, and would not use poison in the mushroom houses for these creatures for obvious reasons. But we should make our houses secure against their inroads.

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.

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.

Cleaning the Mushroom Houses.—After the season's cropping is finished the mushroom houses and cellars should be thoroughly cleaned. Clear out the old beds, and bring outside all the movable floor and shelf boards, scrape up every bit of loose litter or dirt in the place and throw it out, broom down the walls and whatever boarding is left. Whitewash the walls with hot lime wash, and paint every bit of woodwork liberally with crude oil or kerosene. This is to destroy anguillulÆ and other insect and fungus parasites. If you wish to use again the boards brought outside, broom them over and paint them copiously with kerosene. And if your cellar or house has a dirt floor, a heavy sprinkling of very caustic lime water all over it will do good in ridding it of vermin.