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
larvae 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 deg.,
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 larvae 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. Fi. It is caused
by eel worms (Anguillulae). 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 Anguillulae, 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. Anguillulae abound
wherever decaying vegetable matter exists....
The green algae on the outside of flower pots abounds
in the anguillulae.”
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 larvae 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 larvae 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.
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 anguillulae
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.