Circular

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818 No. 79.
C578
ENT uted States Department of Agriculture,

BUREAU OF ENTOMOLOGY,

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

THE BROOD DISEASES OF BEES.

Bye. he PHL iirs. hee.
Apicultural Hxpert.

In view of the widespread distribution of infectious brood diseases
among bees in the United States, it is desirable that all bee keepers
learn to distinguish the diseases when they appear. It frequently hap-
pens that an apiary becomes badly infected before the owner realizes
that any disease is present, or it may be that any dead brood which
may be noticed in the hives is attributed to chilling. In this way dis-
ease gets a start which makes eradication difficult.

There are two recognized forms of disease of the brood, designated as
European and American foul brood, which are particularly virulent. In
some ways these resemble each other, but there are certain distinguishing
characters which make it possible to differentiate the two. Reports are
sometimes received that a colony is infected with both diseases at the
same time, but this is contrary to the experience of those persons most con-
versant with these conditions. While it may be possible for a colony
to have the infection of both diseases at the same time, it is not by any
means the rule, and such cases are probably not authentically reported.
Since both diseases are caused by specific bacilli, there is absolutely
no ground for the idea held by some bee keepers that chilled or starved
brood will turn to one or the other of these diseases. Experience of
the best practical observers is also in keeping with this. .For a discus-
sion of the causes of these diseases the reader is referred to Technical
Series, No. 14, of the Bureau of Entomology, “‘The Bacteria of the
Apiary, with Special Reference to Bee Diseases,’ by Dr. G. F. White.

AMERICAN FOUL BROOD.

American foul brood (often called simply “ foul brood’’) is distributed
thru all parts of the United States, and from the symptoms published in
European ‘journals and texts one is led to believe that it is also the
prevalent brood disease in Europe. Altho it is found in almost all sec-
tions of the United States, there are many localities entirely free from
disease of any kind.

The adult bees of an infected colony are usually rather inactive and
do little toward cleaning out infected material. When the larve are
first affected they turn to a light chocolate color, and in the advanced
stages of decay they become darker, resembling roasted coffee in color.

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Usually the larve are attacked at about the time of capping, and most
of the cells containing infected larvee are capped. As decay proceeds
these cappings become sunken and perforated, and, as the healthy
brood emerges, the comb shows the scattered cells containing larvee
which have died of disease, still capped. The most noticeable charac-
teristic of this infection is the fact that when a small stick is inserted
in a larva which has died of the disease, and slowly removed, the
broken-down tissues adhere to it and will often stretch out for several
inches before breaking. When the larva dries it forms a tightly adher-
ing scale of very dark brown color, which can best be observed when
the comb is held so that a bright light strikes the lower side wall.
Decaying larve which have died of this disease have a very character-
istic odor which resembles a poor quality of glue. This disease seldom
attacks drone or queen larvee. It appears to be much more virulent in
the western part of the United States than in the Kast.

EUROPEAN FOUL BROOD.

European foul brood (often called “black brood’’) is not nearly as
widespread in the United States as is American foul brood, but in certain
parts of the country it has caused enormous losses. It is steadily on
the increase and is constantly being reported from new localities. It is
therefore desirable that bee keepers be on the watch for it.

Adult bees in infected colonies are not very active, but do suc-
ceed in cleaning out some of the dried scales. This disease attacks
larve earlier than does American foul brood, and a comparatively
small percentage of the diseased brood is ever capped. The diseased
larvee which are capped over have sunken and perforated cappings.
The larve when first attacked show a small yellow spot on the body
near the head and move uneasily in the cell. When death occurs they
turn yellow, then brown, and finally almost black. Decaying larve
which have died of this disease do not usually stretch out in a long
thread when a small stick is inserted and slowly removed. Occasion-
ally there is a very slight “‘ropiness,’’ but this is never very marked.
The thoroly dried larve form irregular scales which are not strongly
adherent to the lower side wall of the cell. There is very little odor
from decaying larvee which have died from this disease, and when an
odor is noticeable it is not the “ glue-pot’’ odor of the American foul
brood, but more nearly resembles that of soured dead brood. This disease
attacks drone and queen larve very soon after the colony is infected.
It is as a rule much more infectious than American foul brood and
spreads more rapidly. On the other hand, it sometimes happens that
the disease will disappear of its own accord, a thing which the author
never knew to occur in a genuine case of American foul brood. Euro-
pean foul brood is most destructive during the spring and early summer,
often almost disappearing in late summer and autumn.

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TREATMENT OF INFECTIOUS DISEASES.

The treatment for both American foul brood and European foul brood
is practically the same. It is impossible to give minute directions to
cover every case, but care and common sense will enable any bee keeper
successfully to fight diseases of brood.

Drugs.—Drugs, either to be given directly in food or to be used for
fumigating combs, can not be recommended for either of these diseases.

Shaking treatment.—To cure a colony of either form of foul brood it
is necessary first to remove from the hive all of the infected material.
This is done by shaking the bees into a clean hive on clean frames with
small strips of comb foundation, care being taken that infected honey
does not drop from the infected combs. The healthy brood in the
infected combs may be saved, provided there is enough to make it profit-
able, by piling up combs from several infected hives on one of the
‘weakest of the diseased colonies. After a week or ten days all the brood
which is worth saving will have hatched out, at which time all these
combs should be removed and the colony treated. In the case of box
hives or skeps the bees may be drummed out into another box or pref-
erably into a hive with movable frames. Box hives are hard to inspect
for disease and are a menace to all other bees in the. neighborhood in
a region where disease is present.

The shaking of the bees from combs should be done at a time
when the other bees in the apiary will not rob and thus spread disease,
or under cover. This can be done safely in the evening after bees have
ceased to fly, preferably during a good honey flow. Great care should be
exercised to keep all infected material away from other bees until it
can be completely destroyed or the combs rendered into wax. Wax from
diseased colonies should be rendered by some means in which high heat-
ing is used, and not with a solar wax extractor. The honey from a dis-
eased colony should be diluted to prevent burning and then thoroly
sterilized by hard boiling for at least half an hour, if it is to be fed back
to the bees. If the hive is again used, it should be very thoroly cleaned,
and special care should be taken that no infected honey or comb be
left in the hive.

It is frequently necessary to repeat the treatment by shaking the bees
onto fresh foundation in new frames after four or five days. The bee
keeper or inspector must determine whether this is necessary, but when
there is any doubt it is safer to repeat the operation rather than run the
risk of reinfection. If repeated, the first new combs should be destroyed.
To prevent the bees from deserting the strips of foundation .the queen
may be caged in the hive or a queen-excluding zinc put at the
entrance.

Treatment with bee escape.—The shaking treatment may be modified
so that instead of shaking the bees from the combs the hive is moved

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from its stand, and in its place a clean hive with frames and founda:
tion is set. The queen is at once transferred to the new hive, and the
field bees fly there when they next return from the field. The infected
hive is then placed on top of or close beside the clean hive and a bee
escape placed over the entrance of the hive containing disease, so that
the younger bees and those which later emerge from the cells may leave
the hive but can not return. They therefore join the colony in the new
hive.

Fall treatment.—It it is desirable to treat a colony so late in the fall
that it would be impossible for the bees to prepare for winter, the treat-
ment may be modified by shaking the bees onto combs with plenty of
honey for winter. This will be satisfactory only after brood rearing
has entirely ceased. In such cases disease rarely reappears.

In the Western States. where American foul brood is particularly
virulent, it is desirable thoroly to disinfect the hive by burning the
inside or by chemical means before using it again. This is not always
practised in the Eastern States, where the disease is much milder.
Some persons recommend boiling the hives or disinfecting them with
some reliable disinfectant such as carbolic acid or corrosive sublimate.
It is usually not profitable to save frames because of their comparatively
small value, but if desired they may be disinfected. Great care should
be exercised:in cleaning any apparatus. It does not pay to treat very’
weak colonies. They should either be destroyed at once or several
weak ones be united to make one which is strong enough to build up.

Recently some new “‘ cures’’ have been advocated in the bee journals,
particularly for European foul brood, with a view to saving combs from
infected colonies. The cautious bee keeper will hardly experiment with
such methods, especially when the disease is just starting in his local-
ity or apiary, but will eradicate the disease at once by means already
well tried.

In all-cases great care should be exercised that the bee keeper may
not himself spread the infection by handling healthy colonies before
thoroly disinfecting his hands, hive tools, and even smoker. Since it
takes but a very small amount of infected material to start disease in a
previously healthy colony, it is evident that too much care can not be
taken. In no case should honey from unknown sources be used for
feeding bees. Care should also be exercised in buying queens, since
disease is often transmitted in the candy used in shipping cages.
Combs should not be moved from hive to hive in infected apiaries.

‘“ PICKLE BROOD.”’

There is a diseased condition of the brood called by bee keepers
‘nickle brood,’’ but practically nothing is known of its cause. It is
characterized by a swollen watery appearance of the larva, usually
accompanied by black color of the head. The larvee usually lie on their

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backs in the cell, and the head points upward. The color gradually
changes from light yellow to brown after the larva dies. There is no
ropiness, and the only odor is that of sour decaying matter, not at all
like that of American foul brood. In case the larvee are capped over,
the cappings do not become dark, as’ in the case of the contagious
diseases, but they may be punctured. So far no cause can be given
for this disease, and whether or not it is contagious is a disputed point.
Usually no treatment is necessary beyond feeding during a dearth of
honey, but in very rare cases when the majority of larvee in a comb are
dead from this cause the frame should be removed anda clean comb
put in its place to make it unnecessary for the bees to clean out so
much dead brood.

CHILLED, OVERHEATED, AND STARVED BROOD.

Many different external factors may cause brood to die. Such dead
brood is frequently mistaken, by persons unfamiliar with the brood dis-
eases, for one or the other of them. Careful examination will soon
determine whether dead brood is the result of disease or merely some
outside change. If brood dies from chilling or some other such cause,
it is usually soon carried out by the workers, and the trouble disappears.
No treatment is necessary. Brood which dies from external causes
often produces a strong odor in the colony, but wholly unlike that of
American foul brood, merely that of decaying matter. The color of
such brood varies, but the characteristic colors of the infectious diseases
are usually absent, the ordinary color of dead brood being more nearly
gray.

Approved:

JAMES WILSON,
Secretary of Agriculture.

WASHINGTON, D. C., October 3, 1906.

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