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Issued October 5, 1912.

U. S. DEPARTMENT OF AGRICULTURE,

BUREAU OF ENTOMOLOGY—CIRCULAR

No. 155.

L. O. HOWARD, Entomologist and Chief of Bureau.

INSECTS INJURIOUS TO MUSHROOMS.

BY

C. H. POPENOE,

Entomological Assistant.

WASHINGTON

: GOVERNMENT PRINTING OFFICE

: 1912

BUREAU OF ENTOMOLOGY.

L. O. Howarp, Entomologist and Chief of Bureau.
C. L, Margiatt, Yntomologist and Acting Chief in Absence of Chief.
R. S. Cuiirton, Executive Assistant.
W. F. Tastet, Chief Clerk.

F.. H. CHITTENDEN, in charge of truck crop and stored product insect investigations.
A. D. HoPKINS, in charge of forest insect investigations.

W. D. HUNTER, in charge of southern field crop insect investigations.

EF. M. WEBSTER, in charge of cereal and forage insect investigations.

A. L. QUAINTANCE, in charge of deciduous fruit insect investigations.

E. F. PHILuies, in charge of bee culture.

D. M. Rocers, in charge of preventing spread of moths, field work.

Roiua P. CurRIE, in charge of editorial work.

MABEL CoLcorD, in charge of library.

TRUCK CROP AND STORED PRODUCT INSECT INVESTIGATIONS.
F. H. CHITTENDEN, in charge.

H. M. RUSSELL, C. H. PoPENOE, WILLIAM B. Parker, H. O. MarsH, M, M. HiecuH,
Frep A. JOHNSTON, JOHN HE. GRAF, entomological assistants.

I. J. Conpit, collaborator in California.

W. N. Orpd, collaborator in Oregon.

Tuomas H. Jones, collaborator in Porto Rico.

_ Marion 7. VAN LIlorN, PAULINE M. JOHNSON, ANITA M. BALLINGER, preparatorsé.

II

CiRCcULAR No. 155. . Issued October 5, 1912.
United States Department of Agriculture,

BUREAU OF ENTOMOLOGY.

L. O. HOWARD, Entomologist and Chief of Bureau.

INSECTS INJURIOUS TO MUSHROOMS.

By C. H. PoPeNog,
Entomological Assistant.

Cultivated mushrooms, especially during warm weather, are at-
_tacked by several species of insect pests which frequently destroy
an entire crop, or so curtail the production as to make the industry
unprofitable. Although this injury is at
times serious, little interest has been taken
by entomologists in the matter of its con-
trol, so that there is practically no available
economic literature on the subject. This
circular is of a preliminary nature, as the
investigation of all insects injurious to
mushrooms may not be completed for some
time.

The insects which usually attack culti-
2 vated mushrooms, and those of which com-
Ve plaints are most frequently made, may be
is. divided roughly into four classes, namely,
mushroom maggots, mites, springtails, and Fre. 1.—A mushroom fly, 4 phi-

ochata albidihalteris: Male.

sowbugs. Of these the maggots are the yeucn enlarged., (Original)
most generally injurious, the mites follow
if in order of importance, owing to the difficulty with which their
eradication is accomplished, and then come springtails and sowbugs
in the order named.

44 MUSHROOM MAGGOTS.
| (Sciara multiseta Felt et al.)

The injurious forms commonly known as “mushroom maggots” are
small whitish or yellowish-white maggots usually having black heads.
50985°—Cir, 155—12 1

od INSECTS INJURIOUS TO MUSHROOMS.

They are the young of certain small flies or “ gnats,” two-winged

and mostly black in color, of several species belonging to the fami-
hes Mycetophilide and Phoride, and to the genera Sciara and
Aphiocheta. Of these the species belonging to the genus Sciara are
by far the most common and injurious of mushroom pests. They are
minute in size, measuring about three thirty-seconds of an inch in
length and about one-eighth mch in spread of wings. They are
smoky or dusty black in color. The species attracting most atten-
tion as pests are Sciara multiseta Felt and Sciara agraria Felt. Both
species are, lke the other mushroom gnats, rapid and prolific breed-
ers, especially during warm weather, frequently occurring in mush-
room houses so abundantly as to darken the windows. They may
be readily confused, however, with gnats of the same genus which
breed in manure or in greenhouse soil, and determinations should
always be made by a specialist.

Another common species, Aphiocheta albidihalteris Felt (fig. 1),
superficially resembles the preceding, and has much the same habits,
but as yet has not appeared to cause so much damage as have the
species before mentioned.

The life history of one of the mushroom maggots is about as fol-
lows: The eggs, of which each female is capable of laying nearly
1,000, are generally deposited at the juncture of the stem and cap of
the mushroom, or in the manure or soil at its base. In a warm tem-
perature they may hatch within three days, but in colder weather this
time may be considerably extended. Upon hatching the larve bore
at once into the stem or cap of the mushroom, soon riddling the cap,
and causing the breaking down of the mushroom in a short time.
On account of the perishable nature of their host they pass through
their transformations quickly, the larve feeding for from 7 to 10
days, by which time the entire cap is destroyed. The larve then
enter the ground, each spinning a shght silken cocoon just beneath
the surface, and pupating. The pupa stage lasts from four to
seven days, after which the insects emerge as adults, soon afterwards
pairing and ovipositing for the next generation. Owing to the
immense number of eggs deposited and to the short life-cycle the
rapidity of their increase is remarkable, so that the presence of only
a few insects in the mushroom house at the beginning of the season
may result in the presence of millions after the beginning of warm
weather, thus effectually preventing the cultivation of mushrooms.

CONTROL.

It is evident that in the control of the mushroom maggots measures
should be undertaken early in the season for their elimination from
the mushroom house and precautions observed against their subse-

INSECTS INJURIOUS TO MUSHROOMS. 3

quent entrance. These should begin with the construction of the .
house or cellar. The building should be so constructed as to permit
of effective fumigation and should be fitted with tight screens of fine
wire gauze, suitable to prevent the ingress of the fungus gnats. The
gnats may also be brought into the house through the agency of the
manure used in the compost beds, so that it is well to disinfect or
sterilize this substance by means of steam. This may be accomplished
by placing the manure or soil in vats or boxes, through which steam
pipes, perforated to allow the escape of the steam into the boxes, are
conducted. (See fig.2.) The manure should be heated to a tempera-
ture of 150° F., which will destroy all animal life occurring thereit:
without injury to its capacity for producing mushrooms. Fumiga-
tion with bisulphid of carbon just previous to planting the mushrooms
is also productive of good results in destroying maggots in the com-
post. The bisulphid should be used at a strength of 2 to 4 pounds to
1,000 cubic feet of
space and should
be evaporated in
shallow pans
‘placed in the
highest part of
the house. It is
WOTTON COPANO UCN SOY Ge aga
and evenexplosive |,
when brought into me J Gime box, me Siuineed for the treatment of com-
contact with fire ose (OU GIS)

or sparks, so that care should be used to avoid bringing any fire
into the building during the process of fumigation.

One of the best methods for the destruction of the adults or flies
in their occurrence in mushroom houses is fumigation with tobacco
or nicotine fumigants such as are used in greenhouses. These should
be used in accordance with the directions indicated on the package
for a medium or heavy fumigation.t Used in this manner, and ap-
plied once a week during the bearing season of the mushroom bed.
this method has been se successful in reducing the number of flies
that very little damage, if any, resulted from the larve.

Fumigation with pyrethrum or dusting the powder over the beds
is also effective against the mushroom maggots if taken in time, but
tobacco fumigation may be considered standard for this use.

1The proportion of nicotine in the several preparations varies to such an extent that
no standard dose has as yet been formulated.

& Bee > eter SS PFS =

SS ewe eS

4 INSECTS INJURIOUS TO MUSHROOMS.

THE MUSHROOM MITE.
(Tyroglyphus lintneri Osb.)

The mushroom mite (7yroglyphus lintnert Osb.) (fig. 3) is a
minute, soft-bodied mite, smooth skinned, and white or whitish in
color. It is closely allied to the common cheese mite (Zyroglyphus
siro Lu.) and resembles that species in appearance. It is, if anything,
more prolific than the cheese mite, becoming at times so abundant
in mushroom beds as to cover the surface of the compost, and when
present in such numbers is extremely destructive, feeding upon the
mushrooms in all stages and penetrating the beds and destroying the
mycelium. Indeed, in one case
observed by Mr. August Busck,
of this bureau,’ the mycelium
was destroyed as fast as it grew
from the spawn.

This species is undoubtedly
the cause in many cases of the
failure of the spawn to grow,
which is likely to be attributed
to poor or weak spawn, or to
defective cultural conditions.
The minute size of the mites
causes their presence to be litle
suspected, and the failure of
the spawn to produce mycelium
is not understood. Even under
conditions favorable to the
growth of the mycelium it is
possible for the mites to increase
to such an extent that the en-
tire bed may be killed out.

Besides the injury to the my-
Wic..3—The mushroom mite (Tyropphue . Collum, Mushroom. Mites. Calica

lintneri). Highly magnified. (From damage to the fruiting bodies

een by eating into them, distorting
or destroying the young growth. In the more mature mushrooms the
mites may be found clustered in groups consisting of individuals of
many sizes, usually hidden in the folds between the gills, where they
burrow into the tissue and rapidly break down the caps.

No direct observations bearing on the life history of this species
have been made, but judging from that of related species it is about
as follows: The eggs, which are large in proportion to the size of the

BS”:
mites, are laid in or about the mycelium of the mushroom, or on the

1 Bul. 38, Bur. Ent., U. S. Dept. Agr., p. 32, 1904.

INSECTS INJURIOUS TO MUSHROOMS. 5

young or developing caps. They hatch in a short time into the char-
acteristic six-legged young, which rapidly mature to adults similar to
the one in figure 2. The time from the deposition of the egg to the
maturity of the mite has not, to the writer’s knowledge, been accu-
rately worked out, but undoubtedly occupies only a few days. It is
on this account that the mite is able to increase so rapidly, apparently
as if by magic, and thus give rise to the theory of spontaneous genera-
tion sometimes advanced to explain this condition.

Under certain conditions the hypopus or migratory stage is pro-
cuced. This stage, according to Banks,’ is peculiar to the family
Tyroglyphide, to which this mite belongs, and is quite remarkable.
The mite develops a hard, chitinous covering, has no mouthparts, and
is provided with short legs insufficient for walking. On the ventral
surface of the body is an area provided with sucking disks, by means
of which the hypopus attaches itself to an insect and is so transported
to suitable breeding grounds in other localities. On arrival at a suit-
able breeding place the mite detaches itself from its insect host, molts,
and soon becomes adult. During the hypopus stage the mite takes
no food and causes no injury to the insect which carries it. This
peculiar stage is the natural means for the distribution of the mite to
new localities, and is in many cases responsible for its appearance in
localities far from previously infested beds.

In addition to the way mentioned above, the mite may obtain
access to mushroom houses in infested compost or in spawn from
infested houses. However, the greater part of the infestation prob-
ably takes place through the agency of the small flies which frequent
mushroom houses and which carry the hypopus stage of the mite
from one house to another.

REMEDIES.

Little can be recommended for the control of the mushroom mite
after it has once become established in a house. Owing to the ab-
sence of breathing-pores it is little affected by the fumigants suitable
for the control of the other mushroom pests, while applications of
sulphur, tobacco dust, and other suitable insecticides to the beds
seem only to prove slightly inconvenient to the mite. It is one of
the most stubborn pests with which we have to deal in mushroom
culture, and may be brought into the house in almost any manure
that is used for the bed. When in the hypopus stage it is capable of
prolonged suspension of vitality and is likely to remain in the house
for an unlimited time without death. The only measures, therefore,
that may be considered are those of prevention.

When a house becomes infested, all compost should be gathered
with the utmost care, removed to the outside, and thoroughly disin-

1Proc. U. S. Nat. Mu&., vol. 28, p. 79, 1904.

Eee.

ete

a -_

6 INSECTS INJURIOUS TO MUSHROOMS.

fected by drenching with boiling water, or it may be hauled to a dis-
tance and spread upon the ground as fertilizer, or it may be destroyed
by burning. The ground occupied by the mushroom beds should be
thoroughly scalded, and the woodwork of the mushroom house treated
io a wash of creosote or crude carbolic acid, either of which is distaste-
ful to the mites. After complete disinfection has been accomplished
the house should be screened, to guard against subsequent introduction
of the pest by means of flies. AI] manure forming the beds should be
steamed, according to the directions under the head of mushroom
maggots. Care should be used to purchase spawn only trom unin-

fested houses. With these precautions it is unlikely that trouble will

be experienced from the attacks of the mushroom mite. Close watch
should be kept, however, for any signs of the presence of the mites
in the beds, and the compost destroyed upon their first appearance,
as it 1s impossible to secure good results with mushrooms when in-
fested by these mites. All applications of suffi-
cient strength to destroy the mites are lkewise
injurious to the mushrooms, and it is futile to
attempt to control by any artificial means, once
the mushroom bed becomes infested, as the mites
are buried so deeply in the compost that no insec-
ticide will reach them.
A predaceous mite belonging to the Gamaside
frequently occurs in beds infested by the mush-
room mite, feeding upon the latter, and at times
cP as becoming so numerous as entirely to wipe out the
Achoreutes arma- pest. The gamasid may be known by its longer
aa Lil feaeeers legs and its manner of running swiftly over the
compost or the mushrooms. The writer has seen
cases where the gamasid has occurred in such abundance as greatly
to outnumber its host. This predaceous enemy does not feed on the
mushrooms after the destruction of the mites, but seeks other feeding
grounds, or dies by starvation.

SPRINGTAILS.

(Achoreutes armatum Nicolet et al.)

At times the surface of a mushroom bed becomes alive with minute
brown or black insects, which, when disturbed, leap about lke fleas
in an extremely erratic manner. These are known as springtails,
since the springing is performed by the aid of two short bristles
situated on the anal segment of the abdomen. These insects (Acho-
reutes armatum, see fig. 4) are present in almost all manure, where
they feed on the decaying vegetation present, but on occasion they
may become quite injurious in mushroom houses. A correspondent

ery

pei.

INSECTS INJURIOUS TO MUSHROOMS. 7

in St. Louis, Mo., reported that in one of his mushroom houses a bed
150 feet in length had been completely destroyed by these pests, which
attacked the mushrooms as fast as they appeared, honey-combing
them and rendering them unfit for use. The method of attack
_of this insect is to feed upon the fruiting bodies of the mushrooms,
destroying both the gills and the cap. Hundreds may be found
clustered upon a single mushroom and eating large cavities in the
gills. It appears to be a habit of these insects to congregate in large
numbers on caps which have been slightly injured, in which case
they rapidly destroy mushrooms which would be readily salable if
the injury were not continued. When they occur in large numbers
they are likely to attack even the perfect mushrooms, in aggravated
cases destroying whole beds.

Insects of this group pass through no larval transformation, the
form of the newly hatched young being similar to that of the adult.
They are thus likely to be injurious in the same manner throughout
their life history.

REMEDIES.

The remedial measures applicable to the control of springtails are
to a large extent preventive, as these insects are somewhat difficult
to control when once established in a mushroom bed. They are quite
resistant to tobacco powders, but applications of buhach or pyreth-
rum to the beds are productive of some good. As they usually con-
eregate near the surface of the beds fumigation with hydrocyanic-
acid gas, according to the directions given in Circular 37 of this
bureau, will prove effective in reducing their numbers. The cyanid
should be used at a strength of from 3 to 6 ounces to each 1,000 cubic
feet of air space, which will not prove injurious to the mycelium.

By way of prevention, steaming all manure, as previously sug-
gested for other species, will destroy springtails equally well. Where
possible, it is better to grow the mushrooms at a temperature of about
55° F. than higher, as at low temperatures the springtails breed
much less quickly. Dusting the tops of the beds with powdered lime
is also said to discourage attack by springtatls.

SOWBUGS.

(Armadillidium spp. and Porcellio spp.)

Considerable injury is often accomplished to mushroom beds
through the attacks of oval, grayish, or slate-colored creatures bear-
ing seven pairs of legs. These creatures are not true insects, although
known variously by the terms “ woodlice,” sowbugs, and “ pillbugs.”
Two species, the greenhouse pillbug (Armadillidium vulgare Wa-

ors

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8 INSECTS INJURIOUS TO MUSHROOMS.

treille) and the dooryard sowbug (Porcellio levis Koch), are illus-
trated in figures 5, 6, and 7. ee

Sowbugs live in damp, dark places, such as beneath boards, in
cellars, and in the cracks of sidewalks. When disturbed many spe-
cies roll up to form a ball, lying quite still until the danger is past.
(See fig. 5.) During the night they issue from
their hiding places to feed upon decaying vege-
table matter, molds, and other material present
in damp soils, although at times the roots of
plants and even the green leaves are not es-
chewed.

The young are carried about in a pouch,
formed by several modified anal plates on the
abdomen of the female, until able to shift for
themselves. When released by the female the
young are similar in appearance to the adults,
although much smaller, and are likewise cap-
Fic. 5.—The greenhouse gable of damage. There

pillbug (Armadillidium , 5

vulgare) extended. 1S probably only one

nat) uareed. (On8- generation annually, the

young making their ap-
pearance in the spring and requiring one sum-
mer to reach maturity.

The destruction occasioned by sowbugs is
due to their attacks on the caps or fruiting
bodies of the mushrooms. These they attack

Fic. 6—The greenhouse

while quite small, destroying them or 1njur- pillbug (Armadillidium
ino their appearance. vulgare) contracted.
ne se Satan Much enlarged. (Orig-

They do not, as a rule, inal}

attack the mycelium,

but eat holes in the young “buttons, which,
on the completion of the growth, become much
larger and disfigure the product.

Sowbugs are, more frequently than at first
might be thought, carried into the mushroom
house in compost which has been allowed to
stand outside. The heat of the manure is
relished by them, and they collect in numbers.
Fic. 7.—Dooryard sowbug remaining there throughout the growth of the

nas yea re spawn, but becoming injurious with the first

erowth of the mushrooms. The writer has
seen sowbugs collected in manure piles to such an extent that numbers
aggregating a pint or more in quantity might have been collected
from a shovelful of material.

INSECTS INJURIOUS TO MUSHROOMS. 9
REMEDIES.

Where the mushroom house is small in extent it is possible materi-
ally to reduce the numbers of sowbugs by means of hand picking.
The house may be visited at night, when, by the aid of a lantern,
numbers of sowbugs may be seen crawling about on the earthen
casing of the beds and upon the boards and supports of the benches.
These may be destroyed with a small wooden paddle.

_ It is also possible to secure good results by pouring hot water along

the cracks in the boards and in other places where the “ bugs” may
be concealed by day. This is effective in small establishments, but is
somewhat difficult of application in large houses. In such a case,
fumigation with hydrocyanic-acid gas is an effective remedy. Treat-
ment with sulphur dioxid? is also effective, but this remedy should
be apphed after the mushroom crop has been harvested and the com-
post has been removed.

Another method is to cut small pieces of raw potato, plastering the
wet surface with Paris green, and laying them about on the beds in
the localities affected by the sowbugs. This method is frequently
‘successful in entirely ridding houses of this pest.

CRICKETS.

Among other injurious forms which at times attack mushrooms,
certain crickets are reported as eating into the caps of the mush-
rooms. On the Pacific coast a species known scientifically as Ceu-
thophilus pacificus Thom. has been reported as causing extensive
injury to cultivated mushroom beds.

The remedies for crickets in their injurious occurrence are the
same as those recommended for sowbugs in a previous section of this
circular. Potatoes and carrots may be minced before applying the

Paris green, in order to secure a somewhat thicker coat.

GENERAL SUMMARY.

In the construction of mushroom houses care should be taken to
make the building as tight as possible and with few outlets. If
windows are necessary they should be small and should be screened
with fine wire gauze, which forms an excellent prevention against
the entrance of both maggots and mites, as previously mentioned. If
possible all compost should be steamed before being placed in the
house and the temperature should be kept below 55° F-., as all insects
are more or less dormant at this temperature, and their otherwise

1 See reprint from Bul. 60, Bur. Ent., U. S. Dept. Agriculture, pp. 139-163, Sulphur
Dioxid as an Insecticide.

LDP Ge Rh iii i i OD EB Ore

te eorey-*

—— oe

10 INSECTS INJURIOUS TO MUSHROOMS.

rapid multiplication is thereby greatly checked, reducing infestation
to a minimum. If these recommendations are carefully followed
there should be little necessity for the radical measures of fumigation
or destruction of the beds.

Approved:
JAMES WILSON,
Secretary of Agriculture.
WasuineTon, D. C., April 17, 1912.

oo COPIES ofthis pcblication
may be procured from the SUPERINTEND-
ENT OF DOCUMENTS, Government Printing
Office, Washington, D. C., at 5 cents per copy

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