BEE MALADIES
The
Wax Moth
Surviving a Wax Moth Infestation or How to Produce Fish
Bait Without Really Trying.
Robert N. Brewer Jr. Hiawassee, Georgia USA.
It
was an un-seasonally warm October day in Georgia when I popped the
top on one of my hives to take pictures for a lecture I was to give
in November 2002 Donegal for the Roe Valley and Donegal BKA in Ireland.
I had already taken some fine images that day at another apiary
and expected to finish my project in this one hive. I got quite
a surprise and a photo opportunity that I was not expecting, for
when I finally pried the top loose I was faced with a scene best
left to science fiction movies. The entire hive was literally crawling
with Greater Wax Moth larvae (Galleria mellonella).
If you have never seen or experienced an infestation of wax moths,
I will tell you that words can’t possibly describe the carnage
left behind. They destroy every scrap of wax in the hive; they scar
all of the woodenware and leave behind a muck of webs and droppings.
All one can do is to clean up the whole mess and hope there is enough
hive left to start over. The only up side to an infestation is that
if you happen to be a fisherman, the larvae make great bait and
it requires no labour on your part to produce it!
Wax moths are thought to have originated in Asia. But the point
of origin is really a moot point since they now inhabit most of
the Earth. At some point almost every beekeeper will have an experience
with the Greater Wax Moth, especially those who live in warmer climates.
They are one of the most destructive pests in the apiary, so it
is worth looking at them more closely.
Wax
moths primarily infest improperly stored equipment such as unused
honey supers, frames or anything else containing wax. But they will
invade hives that have been weakened by disease, parasites, queenless
or failing queen colonies, starving colonies or colonies weakened
by swarming or, as in my case, absconded bees. The newly hatched
larvae will grow to a length of about one inch and range in colour
from white to grey. As they move through the hive, the larvae spin
silk-like web tunnels that they attach to woodenware prior to spinning
cocoons for pupation. The scarring, mentioned earlier, occurs as
a result of damage done to the wood by the attachment of these silk
tunnels.
The
wax moth larvae seem to prefer the old, darker wax usually associated
with the brood chamber, but once this is consumed will move on to
cleaner wax in honey supers. It is possible that they are attracted
to the brood chambers by shed bee larvae skins, stored pollen and
honey that they use as food also.
The most effective way to prevent wax moth infestation of hives
is to maintain healthy, vigorous colonies. In a strong colony the
bees will remove any larvae that are unfortunate enough to hatch
and repair any damage that they may have caused.
Stored
equipment can be protected by stacking stored honey supers in a
criss-cross manner, in open sheds to allow for maximum airflow or
by stacking and fumigating with paradichlorobenzene (PDB) crystals.
Electric “bug zappers” or traps can also be effective
against adult moths.
As we have seen an infestation of wax moths is something to be avoided
if at all possible. Proper storing of unused equipment and good
hive husbandry will go a long way toward achieving this goal. Cover
stored supers and brood boxes with sheets of newspapers between
them for some unknown reason moths don’t like them. Unless,
of course, you happen to enjoy fishing. In which case do nothing
and enjoy the bounty.
The
Small Hive Beetle
Introduction
Small hive beetles (Aethina tumida Murray) are native to sub-Saharan
Africa where they are scavengers in colonies of African subspecies
of honey bees. Recently, they have become a significant problem
in parts of the United States and Australia. While currently not
found in Europe, beetle larvae have been found in Portugal in a
queen cage shipped from Texas, USA. Prognosis for reaching and establishing
populations in the UK...very likely! It would seem that the UK is
especially vulnerable to beetle problems due to its wet climate.
Although impossible to predict with precision, the beetle may cause
substantial damage to bee colonies in Northern Ireland. As such,
it is important to understand a little about the beetle so that
one can approach its control in an informed manner.
Figure
1
Description
Newly emerging small hive beetles are light brown in color, becoming
progressively darker (almost black) as their body hardens (Figure
1). The beetles can vary greatly in size (~5.6 mm long and ~3.2
mm wide), possibly depending on diet, climate, etc. Hive beetle
eggs are 1.4 ¥ 0.26 mm (l ¥ w) and pearly white in appearance.
Larval growth rate varies depending on diet; the majority mature
in 10-14 days. Upon full maturation, larvae will have reached a
length and width of 9.5 mm and 1.6 mm respectively. Early-stage
pupae of the beetle are pearly white, having characteristic projections
on the thorax and abdomen. As the body hardens, the pupae darken
until final emergence as adults.
Figure
2
General Biology and Life History
Small hive beetles are endemic scavengers in honey bee colonies
of sub-Saharan Africa. In their native range, the beetles are not
considered major economic pests to African subspecies of honey bees
although they may damage or even totally destroy the occasional
weakened colony. Economically, they are often considered less important
than the cosmopolitan greater and lesser wax moths although they
probably serve the same function (to clean up dead or weakened honey
bee colonies). Most beetle damage comes from the feeding habits
of adults and larvae which eat honey, pollen, and, preferentially,
bee brood (Figure 2). However, as a secondary effect of adult and
larval feeding, stored honey in a colony is rendered useless as
it quickly fouls and ferments due to significant beetle populations,
likely owing to beetle defecation.
Upon emergence from the ground, adult beetles search for honey bee
colonies, probably identifying the host colony by a suite of olfactory
cues. The beetles fly before or just after dusk and odors from various
hive products (honey, pollen) and adult bees are very attractive
to flying beetles. Upon entering the host colony, beetles seek out
cracks and crevices where they hide from bee aggression.
Figure
3
Remarkably, at least some subspecies of African honey bees station
guards around the cracks where beetles hide (Figure 3). The ‘prison’
guards keep the beetles confined to the cracks and out of the brood
combs where there is an ample supply of honey, pollen, and brood
which promote beetle reproduction. Despite being confined, the beetles
are able to stay alive by tricking their captors into feeding them
(Video 1) credit Gerald Kastberger and Otmar Wilder.
If allowed to reproduce, female beetles will lay eggs directly onto
food sources such as pollen or brood combs.
Click
here to view Video 1 (Must have
a video player installed on their computer in order to view)
Alternatively, female beetles may deposit irregular masses of eggs
in crevices or cavities away from the bees as female ovipositors
are long and flexible, being perfectly designed to lay eggs in tiny
and concealed places. It has been speculated that a female beetle
may lay 1,000 eggs in her lifetime. Humidity appears to be a crucial
factor influencing hatching rates, as beetle eggs are prone to desiccation
if exposed to circulating air and relative humidity below 50%.
Hatching larvae immediately begin feeding on whatever food source
is available including honey, pollen, and bee brood although they
have demonstrated a preference for bee brood. Maturation time for
larvae is generally 10-14 days, although some were shown to feed
for 29 days. Once the larvae have finished feeding, a ‘wandering’
phase is initiated where larvae leave the food source and migrate
out of the colony to find suitable soil in which to pupate. Despite
that larvae may migrate some distance from the hive in an effort
to find ideal soil, most beetle larvae, pupae and newly eclosed
adults are found within 90 cm of the hive. Nearly 80% of the larvae
burrow down into the soil less than 10 cm from the soil surface
but not generally more than 20 cm. Beetle larvae need moist soils
in order to pupate successfully.
Figure
4
Once larvae cease burrowing, they construct a smooth-walled, earthen
cell in which they pupate (Figure 4). The period of time spent in
the ground pupating can vary greatly depending on factors such as
soil temperature, etc. However, the majority of adults emerge after
being in the soil 3-4 weeks. Upon adult emergence, the entire life
cycle begins again. The turnover rate from egg to adult can be as
little as 4-6 weeks; consequently, there may be as many as 6 generations
in a 12-month period under moderate climatic conditions.
Impact and Control in Introduced Regions
Beetle damage in European colonies follows the characteristic 1)
beetle invasion into colonies, 2) population build-up of beetles,
3) reproduction of beetles, 4) significant damage to brood, pollen,
and honey stores by scores of feeding larvae, 5) mass exodus of
larvae from the hive, 6) pupation in the soil, and 7) emergence
as adults and subsequent re-infestation of colonies.
Beetle damage in Africa often is restricted to weakened or diseased
colonies while in its introduced range, beetles may damage weak
and strong colonies alike. Adult and larval beetles can be a significant
problem in the honey house. As a result, beekeepers realize the
necessity of extracting honey quickly and moving the equipment out
of honey houses to discourage ensuing build-up of beetle larvae.
Further, stored supers of honey or supers containing pollen residues
are prime targets for beetle reproduction and subsequent damage.
The queen and package bee industry is also negatively affected in
areas where beetles occur.
Many beetle control schemes have been tested.
These schemes are reviewed in the following articles published in
the American Bee Journal:
Ellis, J.D. 2005. Progress Towards Controlling Small Hive Beetles
with IPM: Knowing Our Options. American Bee Journal 145(2): 115-119.
Ellis, J.D. 2005. Progress Towards Controlling Small Hive Beetles
with IPM: Integrating Current Treatments. American Bee Journal 145(3):
207-210.
Univ.Prof.Dr. Gerald Kastberger, Institut f�r Zoologie, Universit�t Graz, A 8010 Graz
Conclusion
In conclusion, Northern Ireland remains vulnerable to damage associated
with small hive beetles. It is important that beekeepers in Northern
Ireland and the UK remain prudent when working their hives. Be ready
for the beetle; you can bet that it will be ready for you! If you
have any questions regarding the small hive beetle, do not hesitate
to email me: jdellis@uga.edu