“The
Two R’s: A Paradigm Shift in Beekeeping”
By
Dr.
Malcolm T. Sanford
http://apis.shorturl.com
By the time you read this, my good friend
Laurence Cutts will have retired as
Africanized honey bees came to
Laurence has been a champion for
If all that above wasn’t enough, the appearance
of antibiotic-resistant American foulbrood is now occurring on his watch. Finally, he was faced with introduction of
the small hive beetle, Aethina tumida in 1998.
Laurence came through all these crises with a mixture of confidence and
humor that provided a clearing for other beekeepers to do the same. One of his most important skills is the
ability to boil circumstances down to a few pithy words that call to his
colleague beekeepers. His latest
pronouncement is the subject of this column, that the
two R’s of beekeeping: Resistance and Residues now constitute a paradigm shift
in the craft.
The history of mite resistance began in Europe
where populations first became resistant to fluvalinate
in
The appearance of resistance to both miticides and antibiotics looks to be yet another example
of Garrett Hardin’s "Tragedy of the Commons."2 Dr. Marjorie Hoy, eminent scholar - Davies,
Fischer and Eckes professor of biological control, of
the Department of Entomology and Nematology here at
the University of Florida, has given a number of seminars on the development of
the phenomenon, the source of much of the information provided here. She says
it is strictly a matter of the number of applications, the residue length, and
the genetics of the pest, and is the collective fault of both the companies
producing pesticides and consumers using them. . Her conclusion is that the
only truly effective way to prevent resistance is to stop using pesticides.
If one looks at other examples of resistance to
pesticides in production agriculture, it becomes more obvious why this occurred
for Varroa. Perhaps the most important factor is
prolonged exposure to one pesticide. Certainly this was the case with Apistan®, the only legal, effective material applied for
over a decade to many generations of mites. Selection pressure was also very
high. Apistan® may have been too good in restrospect. It killed off over 98 percent of the mites,
but didn’t get them all. Those left over became a potent source for a resistant
population to emerge. The idea that bee populations must be cleared totally of Varroa also contributed greatly. In the beginning and
continuing to this day, the concept of Varroa
eradication (i.e. "Varroa-free") persists.
As a result, many beekeepers treat when they see only one mite; some leave
treatments in over prolonged periods and others may apply the material prophylactically, just like treating for American foulbrood
using Terramycin®, which most believe resulted in a
resistant causative organism. Other factors that contributed were strong links
between Varroa and its host (they feed and reproduce
only on honey bees). The ability to be carried on the backs of flying bees from
one colony to another adds a significant re infestation dimension.
Factors responsible for development of
resistance to pesticides, according to Dr. Hoy, are generally grouped into two
major categories: controlled and uncontrolled. Unfortunately, most fall into
the latter category. In general, these are genetic, biological and ecological.
The mite’s genetics and biology remain much of an enigma. Its ecology does
too. This kind of basic study,
unfortunately, is often subrogated to pesticide development and application.
It is not surprising that most research and
funding in Varroa control has
concentrated on toxicological work. This is the one area where the beekeeper
and researcher have the best and easiest control. In this kind of work,
formulations and applications can be actively tweaked and their effectiveness
quickly measured. It is also where the money is. There is little incentive on
the part of entrepreneurs to invest in other areas. This is the case with
natural products or processes, which although they may be effective, do not
represent the best possible return on an economic investment. Again much of
this is also true in other forms of production agriculture. Indeed, the loss of
legally registered chemicals in small crops not warranting huge economic
investments continues to be a crisis all across the agricultural spectrum.
According to Dr. Hoy, researchers have developed
models of pesticide resistance where the phenomenon has been detected. However,
debate continues about how effective each is. Apiculture appears to have gone
through several types on its way to its present situation. Saturation uses high
doses of chemicals in an attempt to overcome any resistance that might be
present. This is often employed for high-value crops like apples. Synergists
have even been used to make already-toxic materials more poisonous. These are
very hard on non target organisms and the environment. However, in many systems
of this nature resistance appears.
Much of this is applicable for Varroa. In the beginning, low treatment thresholds, the
idea of "mite-free colonies," meant that a lot of treatment was
probably carried out that was not absolutely necessary. The now-illegal use of Maverik®-soaked wooden strips, originally carrying a
Section 18 label, is an example of saturation, as is reported use of other non
registered materials (e.g. amitraz formulated in Ovicin®).3
Another strategy is moderation. Its philosophy
is to reduce the selective pressure and conserve organisms (genes) that are
susceptible. This means less frequent applications with relatively low dosages
of less toxic chemicals. Some beekeepers are moving in this direction, applying
materials only when absolutely necessary and using less than the recommended
dosages. Unfortunately, there is controversy in this arena, with some
investigators suggesting that underdosing actually
contributes to resistance development. This points to
the fact that the genetic cause of resistance is often unknown. In addition,
the lack of suitable action threshold levels for Varroa
works against this concept .
Multiple attack appears
to be the model beekeeping is now leaning toward. This is characterized as a
rotational philosophy involving several pesticides. Again this has been
employed in other high-value crops and some medical emergencies. Whether to
rotate or mix chemicals is vexing, according to Dr. Hoy. Mixing might enable
them to be used at lower dosages. Beekeepers now find themselves with two legal
materials. Whether to choose mixing or rotating, however, is a question that
cannot easily be answered in this case because there is not enough information
about the mechanism of resistance by Varroa. Because
two classes of pesticides (pyrethroids and
organophosphates) are being employed, however, rotation is considered the best
strategy and beekeepers are asked not to use both materials simultaneously.
Another problem found in production agriculture
is that after pesticide use, pest populations may rebound to higher levels than
before. This resurgence is often the result of killing off natural enemies of
the pest species during the application process. To date, no such organisms
have been found for Varroa and this does not appear
to be an issue. Finally, replacement can occur in many systems. Organisms that
are not a problem or pest may become one as a consequence of trying to control
another pest species. The specter of the small hive beetle for beekeeping is
raised here. Is it possible that the beetle has been around a longer time than
thought and only showed itself as problematic after colonies were exposed to
chronic dosages of pesticides for Varroa control. I have heard
a number of talks where both researchers and regulators say that controlling
hive beetles when Varroa is not first controlled is a
recipe for disaster.
Other strategies to reduce pesticides include
the use of smoke. Other so-called soft chemicals such as natural acids,
essential oils or botanicals are also a possibility. Although a few of these
"natural products" have been shown to be somewhat effective, they do
not kill the number of mites as do registered hard pesticides. However,
resistance to these materials may not prove to be as problematic. Methods in applying
such chemicals, however, have not been worked out, are full of risk for bees
and the action thresholds are unknown.
It is useful to remember that most natural products or biopesticides are poisonous compounds that plants have made
to ensure their consumption more risky and less likely. Their use may also be
construed as illegal or non registered materials by regulatory authorities, and
they are capable of contaminating a honey crop.
In the end, as Dr. Hoy recommends, only by
reducing use of pesticides can beekeepers come to grips with either effects of
sub lethal pesticide doses or resistance. This is the stated goal of integrated
pest management (IPM), a technology that relies on a careful estimation of the
pest population. The number of insects (or mites) causing measurable economic
loss to a crop (or bee colony) is referred to as the economic injury level
(EIL). IPM practitioners attempt to find a level of pest population that will
provide the best indication that economic injury is likely to occur. At that
point, and only at that point, are active measures (e.g. pesticide application)
taken to reduce the pest population. This is called
the economic threshold (ET). For example, in a bean crop it might be determined
that only when there is a certain amount of leaf damage, which translates into
a specific number of caterpillars on a plant, is pesticide application
necessary. A key element here is the realization that some pest population will
always be present in beans and that economic production can be supported at
some level without treatment. A corollary is that eradication is impossible and
should be dismissed as a possibility.
There are other ways besides pesticides to keep
the mite populations below damaging levels. These include trapping them in
drone brood, on sticky boards and by specially designed bottom boards. Another
strategy is to identify Varroa-tolerant honey bees
and then propagate them. This is currently being done through the Baton Rouge
Bee Laboratory’s release of Russian bees and development of SMR stock.
Most of
the control methods suggested above are active. They are applied or exerted by
the beekeeper. However, another group should not be forgotten. These are
referred to as passive, or collectively called "good bee management."
With all the folderol about mites, and now the small hive beetle, the fact that
honey bees can often take adequate care of themselves is easily overlooked.
Resistance runs in the company of residues
according to Laurence Cutts. One of the first responses to resistance,
common in past agricultural practice, is applying more and more chemical
control as the problems increase. This
no doubt has occurred in beekeeping operations.
Although it is not well known why, the appearance of chloramphenicol
in Chinese honey may be a response to resistance by American foulbrood to oxytetracycline (Terramycin®). Study in
Certainly, the continued application of both fluvalinate and now coumaphos
hastens an end to the era that Laurence Cutts
characterizes as that of the “silver bullets”of mite
control. Thus, he gracefully exits the
stage as an advocate for Integrated Pest Management (IPM), carrying the message
that the use of this technology, developed by dedicated researchers like Dr.
Hoy has the best chance at present to keep the two R’s of beekeeping at bay.
References:
1.
5th meeting of the integrated
group for Varroa control, June 2000, World Wide Web
site accessed August 25, 2003 <http://www.apis.admin.ch/english/host/pdf/alternativ/bern.pdf>.
2.
World Wide Web site accessed August 25,
2003 <http://members.aol.com/trajcom/private/trajcom.htm>.
3.
Elzen,
P. J., Baxter, J.R., Spivak, M., Wilson, W.T. Amitraz resistance in Varroa: new
discovery in
4.
S. Bogdanov and
colleagues, Acaricide Residues in Honey Beeswax and Propolis, 1999, World Wide Web site accessed August 25,
2003 <http://www.apis.admin.ch/english/pdf/BeeProducts/Acaricides_e.pdf>