One of the interesting observations made by Martha Gilliam when she was looking into these kinds of pesticide/microbe relationship in the beehive (in the 1970s) is about yeasts and molds.
She reported that in Arizona (at the Tucson Lab), free flying bees that were not exposed to pesticides or other stresses (like caging) did not have yeast in their guts.
Once the bees are caged, fed sugar (even while still free flying), or challenged with pesticides, it is clear that the microflora composition changes.
Yeosts lsoloted from Honey Bees, Apis mellifera fed 2,4D and antibiotics 19?4
"Yeasts were rnore prevalent than Enterobacteriaceae
(Gilliam and X,{orton, 1974)
or fungi (Gilliam et al., 1974) in caged bees
fed 2,4-D, antibiotics, or pollen patties.
Yet, Entcrobacteriaceae (Gilliam ancl
Valcntine, 1973) and fungi (Gilliam and
Prcsb, 1972) r\:ere present in more guts of
bees from frcc-flying colonies than in guts
of becs from caged colonies. However, we
have been unsucccssful in attcmpts to iso-
Iate yeasts from the intestines of adult
worker bees from free-flying colonies (Gilliam,
1973). In the prescnl experiments,
yeasts did not appcar in bee guts until thc
colonies had been cagcd ancl fed experimental
diets for 30-40 days. Therefore, the
intestinal ycast flora of adult rvorker bees
in Arizona appears to develop under conditions
of stress such as caging of colonics,
feeciing artificial diets, or feeding 2,4-D to
colonies. llor.ever, not all bee guts we cxaminecl
in tliese experirlents containecl
.veasts."
Are Yeasts Present in Adult Worker
Honey Beeel as a Consequence of Stress?2'3
MARTHA GILLIAM
Agricultural Research Service, USDA'
2000'tr. Allen Road, Tucson, Arizona 85719
Annals of the Entomological Society of America
Volume 66, Nunrber 5, p. 1176, September 1973
"Yeasts have been found in the crops of diseased honey
bees (Burnside 1930), and Giordani (1952) assumed a
connection between bee pathogens and the presence of
yeasts. Hajsig (1959) found extensive development of
Candi,d,a pnlcherrima in bees treated with terramycin.
Also, Mitroiu et a1. (1966) noted a remarkable increase
in the volume of yeastlike fungi in the intestines of bees
fed sugar syrup supplemented r,vith antibiotics. Toma5ec
(1957) established that antibiotics fed to bees completelv
changed the bacterial flora of the intestine. After caged
bees were fed terramycin, the normal flora almost completely
disappeared, and yeasts developed rapidly.
Kluge (1963) concluded that the normal intestinal microflora
of the honey bee has a fungistatic action, since bees led antibiotics contained yeasts and fungi in their
recta. She stated that the fungus spores normally present
in small numbers in pollen had evidently germinated
and actively multiplied in the guts of the bees lacking
bacterial flora.
I suggest therefore that yeasts in adult worker honey
bees may be indicators of a stress condition since few, if
any, yeasts remain viable in the intestines of honey bees
not subjected to stress. I suggest further that placing
bees in a cage for laboratory studies constitutes stress,
and that in this and other kinds of stress, yeasts can be
readily isolated from the intestinal contents of adult
worker honey bees."
...and from The Micoflora of Adult Worker Honeybees, apis mellifera: Effects of 2,4,5-T and Caging Bee Colonies
Journal of Invertebrate Pathology 30, 50-54 1977
"Molds were most prevalent in
bees from free-flying control colonies fed sucrose, and yeasts were found most often in bees from
caged colonies fed 2,4,5-T."
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