HOME AND FARM MAGAZINE SECTION
Bee Infection Cured by Heat
By L. F. White, M. D., Ph. D.
O reduce th e losses due to bee dis­
eases beekeepers have o ften em­
ployed h e a t in one form or a n ­
other. T he d irect flam e has been used
in scorching or b u rn in g th e inside of
h iv es th a t have housed infected col­
onies. B efore being fed back to bees
honey is o ften heated fo r the purpose
o f destro y in g the germ s of bee dis
eases, should an y be present. H eat is
used in th e rendering of wax and in
th e m aking o f comb foundation. I t is
n a tu r a l and v ery ap p ro p riate, th ere­
fo re th a t beekeepers should inquire
a b o u t th e am ount of h eatin g th a t is
necessary to destroy th e germ s th a t
produce diseases among bees.
As no w ork had been done to d e te r­
m ine the fa c ts relativ e to th is question
w ith any degree o f accuracy, th e w ri­
te r has perform ed durin g tho la st tw o
y ears a num ber o f experim ents for the
purpose of ascertain in g them. I t may
b e of in te re st to beekeepers to know
in a goneral w ay how th ese experim ents
w ere made. An aqueous suspension of
la rv a e sick or dead of the disease is
m ade and placed in a sm all glass tube.
T his tube is immersed in w ater of the
te m p e ra tu re desired in tho heating.
A fte r th e germ -containing m aterial is
h eate d in this way it m ust be tested
to determ ine w hether or not th e germ s
h a v e been destroyed. In the case of
A m erican foul brood th is can be done
by inoculating a suitablo artific ia l
medium w ith the heated m aterial and
observing th e presence or absence o f
grow th of bacillus larv ae, th e germ of
th is disease.
T
Testing for Disease.
»
A s th ere is no a rtific ia l medium
now know n suitable fo r cu ltiv a tin g
th o in fectin g agent of eith er E uro­
pean foul brood, sacbrood, or Nosema
disease, h ealth y colonies of bees must
bo inoculated in m aking the test in
ease of th ese diseases. T his is done by
feed in g th e bees the heated germ -con­
ta in in g m aterial in sirup. If th e d is­
ease is produced by th is feeding,
n a tu ra lly th in fectin g agent has not
been d e stro y 'd by it. By repeated ex
perim en ts o f th is kind in which th e
le m p e ra tu re used in th o h eatin g is
v aried , th e minimum tem p eratu re a t
■which any virus is k illed can be d e­
term ined.
T h irteen ex p erim en ts for
E uropean foul brood, tw en ty two for
aacbrood and tw en ty fo r Nosem a d is­
ease have been made in which h ealth y
colonies w ere inoculated w ith heated
gprm contain in g m aterial from these
th re e diseases, respectively. In th e last
disease th e stom achs from diseased
bees fu rn ish ed th e germ co n tain in g
m aterial fo r h eatin g and feeding. In
th ese experim ents th e tem p eratu re was
m ain tain ed for 10 m inutes as a rule.
N early a cen tu ry and a h alf ago the
nam e “ foul b ro o d ” w as used for a
d e stru ctiv e brood diso rd er of bees, and
fo r alm ost a cen tu ry la te r it w as a p ­
p a re n tly th e custom to diagnose as
foul brood any d estru ctiv e disease of
brood. A bout h a lf a cen tu ry ago bee
keepers began to note th a t »11 of the
brood diseases are not th e same. They
began, th erefo re, to w rite of d iffe re n t
form s of foul brood. A t th e presen t
tim e it is known th a t th ere are a t
le a st th ree infectio u s diseases of th e
brood of bees. All o f these diseases
are more or less d estru ctiv e, and it is
q u ite lik ely th a t each of them has now
and th en been diagnosed as foul
brood. In A m erica th ese brood d is­
eases are now known as E uropean foul
brood, A m erican foul brood and sac
brood.
Foul Broods.
In E uropean foul brood d eath oc­
curs early, th e larv ae dying usually b e ­
fore th e tim e fa r cell capping. T here
is no v iscid ity (ropiness) to th e d e­
caying larv ae as a ru le, and no p ro ­
nounced odor present.
N um erous sam ples of th is disease
have been ex am in e! from th e U nited
S tates, and some from C anada. Its
presence also . in E ngland, G erm any,
S w itzerlan d and D enm ark is strongly
suggested by w ritte n rep o rts from
these countries. I t is very probable
th a t the disease has a much w ider
geographical d istrib u tio n th an these
fa c ts indicate.
Two y ears ago th e fa c t w as dem on­
strated th a t the germ causing Euro
pean foul brood is th e m icroorganism
to which th e nam e b acillus pin ton is
tho evidence a t hand i t seems most
probable th a t th e disorder encountered
by D onhoff and th e one encountered
by Z ander are one a n ! th e sam e dis
ease.
Aside from rediscovering th e diseaso,
Z ander has id en tified the germ caus
ing it as a protozoan (a one-eelled ani
mal p arasite and has given to it the
nam e Nosema apis. For th e disease he
has used the name “ Nosem a Seuche. ”
T his is an ap p ro p riate one, as it sug
gests som ew hat th e n atu re of the dis
ease. The namo “ Nosema d ise a se ,”
which th e w riter suggests as the com
nion name fo r th is disease, is, it will
be observed, only a tra n sla tio n of the
G erm an nam e used by Zander.
The germ Nosema apis gains e n ­
tra n c e to the body of th e bee by w ay
of th e alim en tary canal. In the w alls
o f th e stom ach th e grow th and m ulti
p lic a tio n 'o f the p araiste ta k e place to
an enorm ous ex ten t, causing the a b ­
norm al ap p earance m anifested by the
organ. W hen tho disease reaches an
advanced stag e th e stom ach is w hite
and frag ile and reveals upon a m icro­
scopic exam ination the presence of the
p arasite in very large num bers. In the
spring of th e y ear, especially, many
weak colonies show upon exam ination
a high percentage of Nosema infected
bees, tju ite o ften , indeed, in tho ex­
am inations th a t have been made of
such colonies, 30 to 90 per eent of tho
bees in sampl is tak en from them were
found to be in fected w ith the parasite.
It is an in terestin g and im portant fact
th a t a very largo num ber of colonies
which are strong and ap p aren tly doing
well are found u|>on exainiiiation to
contain a t least a small percentage of
Nosema infected bees.
(4) The minimum tem perature for
Noaema disease lies betw een 55* C.
(131* F.) and 00* C. (140* F .), bo-
ing approxim ately 57* C. (134.G* F .).
It will be noted, therefore, th a t 63*
C. (145.4* F .) fo r European foul brood,
98* C. 208.4* F.) fo r American fonl
brood. 58* C. 136.4’ F .) for sacbrood
and 57* C. 134.6* F .) for Nosema dis-
ease are th e approxim ate minimum
tem peratures a t which the germs of
these diseases, respetcivelv, are de­
stroyed. Since there are varying fac­
tors in experim ents of this nature th a t
tend to produce slight variations in re­
sults, these tem peratures are referred
to as being approxim ate. It is probable
th a t fu tu re experim ents may cause
slight changes to be made in these con­
clusions. N othing more than a com­
parativ ely slight variation is to be ex­
pected, however. Tn practice the bee-
keej>er, in destroying these germs by
heating, will n aturally use a quantity
of heat som ewhat in exeess of the
minimum am ount th a t is absolutely
uecessary.
Homo generalizations may now bs
made which will be of interest to the
beekeeper. The m elting point of bees­
wax is betw een 62* C. (143.6* F .) and
64* C. (147.2® F .), inclusive. I t will
bo observed th a t this same tem pera­
ture in 10 m inutes will destroy the
germ causing European foul brood, and
th a t it is about 10* F. above th a t which
will destroy the germ s of sacbrood
and Nosema disease. A fu rth e r in te r­
esting generalization may be made con­
cerning the heating of honey. Honey
when heated to 160® F. reaches a tem ­
perature 15° F. above the tem perature
necessary to destroy the germ of Euro­
pean foul brood and about 25® F. above
the tem perature th a t will destroy the
infecting agents of sacbrood and
Nosema disease. The in fectin g agent«
of these three diseases of the bee,
therefore, will be destroyed when the
tem perature of 160* F. is used in the
comm ercial handling of honey. F inally,
it is believed that, the results of this
work, on the therm al death point of
the viruses of the bee diseases will be
directly applicable to the control of
these diseases.
given. In a p aper announcing the fact
it was s ta te d th a t th o studies then
m ade in d icated th a t th e germ is easily
killed by heat. T his b elief has been
confirm ed b y fu rth e r experim ents.
A m erican foul brood is th e disease
of the brood of bees th a t is b est known
to beekeepers and is th e one the pres­
ence of w hich th ey have been able to
recognize m ost easily. In th is disease
th e larv ae usually die a fte r th e cells
co n tain in g them are capped. The dis­
ease is ch aracterized especially by the
m arked v iscid ity (ropiness) m anifest
ed by th e d ecaying larv ae th a t are
dead o f th e disease. T he pronounced
odor noticeable w ith in hives housing
colonies a ffe c te d b y th is disease, espe­
cially in its la te r stages, is another
well known ch aracteristic.
U ntil seven y ears ago th e cause of
A m erican foul brood w as not known.
A t th a t tim e th e fa c t was demon
stra te d positiv ely th a t th e germ caus
ing the disease is th e one to which the
name bacillus larvae is given.
Tho fa c ts obtained to d ate are too
m eager to ju s tify a n y th in g more than
a general statem en t regarding the
minim um am ount of h eatin g th a t can
be employed in ren d erin g m aterial con­
ta in in g th e germ o f A m erican foul
brood non-infectious. T ak in g rath e r
wide lim its, it may safely be said that
th e minim um tem p eratu re at which
th is can be done, if th e tem perature is
applied fo r 10 m inutes, lies somewhere
betw een 90 degrees C. (194 degrees F.)
Summary.
and 100 degrees G. (212 degrees F .b
Tho resu lts of these experim ents
It seems q u ite probable, indeed, th at
a tem p eratu re less th an 98 degrees t i.liow th a t when th ey are m aintained
(208.4 degrees P .) will suffice if ap fo r 10 m inutes th e •ninimiini tem pera
plied for 10 m inutes. When 100 de tures th a t can be used for destroying
grees C. w as used the spores of baeeil the germ s of the four bee diseases now-
Itis larv ae were k illed in less than five known to be infectious are as follows:
(1) Tho minim um tem p eratu re for
m inutes.
European foul brood lies somewhere
Sacbrood.
betw een 60* ('. (140* F .) and 65" G.
O bservant beekeepers have for m any (149* F .), being approxim ately 83* •
years noted th e prepence of dead brood (145.4* F .).
which seemed to them to be d ifferen t
(2) The minimum tem p eratu re for
from th a t dead of foul brood Some A m erican foul brood lies somewhere be YOU CAN EARN $ 5 0 .0 0 PE ” ,t? * X
earless Improved Standard
w ere inclined to believe th a t the dis tw een 90*
(194* F.) and 100* G.
Well Drilling Machine.
ease was an infectious one; a larg er (212*) F„ being probably less than
Drill« through any formatxia.
______
F iv e year» ahead of any od»«r.
num ber ap p aren tly w ere disposed to 98° <’. (208.4* F.).
H m record of drilling I ' 0 fret
ascribe th e trouble to such causes as
(3) The m inim um tem perature for
a n d d riv in g caaing m 9 Iwxu».
an u n sa tisfacto ry oueen. starv atio n , sacbrood lies som ewhere betw een 55* A n o th er record where 7 0 fret w »»dnH rdoo 2 4 gal dntillatn
a t 9c per gal O n e man can operate. 1 lecthcafly natupped M
and the like. This brood disease has G. (111.31* F .) and 60* G. (140° F.), be re n tin g mghl«. f-'idungiah. Engine ignition. Catalogue V t
REIERSON MACHINERY CO., M a n frt. Portland. O r»
been recently dem onstrated to be an ing approxim ately 58* G. (136.4* F .).
infectious one, and th e name “ sac
V
b ro o d ” hns been given to it. L arvae
th a t die of th is disease do so alm ost in
v ariab ly a fte r th e tim e of cell cap
ping. The most c h aracteristic symp
tom of th e disease is th e saelike ap
pearance o f th e dead larv ae when they
are rem oved from the cell. This fact
suggested th e name “ sacb ro o d ” for
th e disease.
More th an a year ago it was again
th e w r ite r ’s fo rtu n e to determ ine the
cause o f an o th er brood disease. Un
lik e th e cause o f eith er European foul
brood or A m erican foul brood, th e in ­
fectin g ag en t causing sacbrood has not
vet been seen. It w as dem onstrated,
how ever, th a t th e in fe c tin g agent in
th is disease passes thro u g h the pores
of earth en w are filters. F o r th is reason
th e cause of sacbrood is spoken o f ns
a filte ra b le virus.
In a p ap er announcing th e cause of
sacbrood the statem en t is made th a t
th e germ causing th e disease is de
stroyed by a com p arativ ely small
am ount o f beat. T his b elief is con­
firm ed by th e resu lts o f experim ents.
V ery little is known about th e dis I
eases of ad u lt bees. M any names have
been used for th e purpose o f desig
r a tin g them , b u t the num ber of such
diseases is p robably sm all. T here is
only one ad u lt disease th a t can be
diagnosed a t present by lab o rato ry
m ethods. T his one is th e Nosem a d is­
ease.
Nosema Disease
F if ty seven years ago Dr. D iinhotf
m ade a more or less b rie f study of a |
disease of ad u lt bees in G erm any. He
observed th a t th e stom ach was the
organ th a t was p rim arily affected . By
feeding to h ealth y colonies in sirup the
crushed stom achs from affected bees
D onhoff dem onstrated th a t th e disease
4511 MORRISON STREET
could be tra n sm itte d to h ealth y colo­
nies. I t w as th erefo re infectious.
PORTLAND
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OREGON
The work o f D bnboff had been prsc
tically fo rg o tten , ap p aren tly , when
Z ander, o f E rlangen, G erm any, fiv e
y ears ago observed th e proses«« o f a
li sc ass am ong tho a d u lt bees. From
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