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.
[Illustration: FIG. 25. MUSHROOM AFFECTED WITH BLACK SPOT.]
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.
[Illustration: 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.
=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.