In response to Peter's enquiry, there was an interesting paper published
last year by Stephen Martin, Patti Elzen and William Rubink:
2002. Effect of acaricide resistance on reproductive ability of the
honey bee mite Varroa destructor. Exp. Appl. Acarology. 27: 195-207.
The author's observed that mites from a fluvalinate resistant
population lay just as many eggs and rear just as many fertile offspring
as mites from a fluvalinate susceptible population (abstract below).
Seeing as there is little consequence to mite reproduction rate to
carry the resistance gene(s) it is not suprising when Max reports low
rates of reversion to fluvalenate susceptiblity among resistant
populations in Europe. There was a great study documenting the slow
rate of reversion in an isolated population in Friuli Italy (abstract
below).
The rate at which populations of pests and microbial pathogens develop
resistance is a complicated issue. It took years of oxytetracycline use
before resistance was detected among Paenibacillus larvae subsp. larvae
strains, but coumpahos resistant Varroa in the USA appeared very quickly
after Check Mite was introduced. Prudent resistance management right
from the introduction of a new chemical, seems the best way to hedge my
bet and keep a useful product around for the longest period of time. I
have enjoyed following this thread.
Adony
Experimental and Applied Acarology
27 (3): 195-207, 2002
Effect of Acaricide Resistance on Reproductive Ability of the Honey Bee
Mite Varroa Destructor
Stephen J. Martin
Laboratory of Apiculture and Social Insects, Department of Animal and
Plant Sciences, Sheffield University, Western Bank, Sheffield, S10 2TN,
UK Author for correspondence (Tel.: (0)114-2220149; Fax: (0)114-2220002;
E-mail: [log in to unmask])
Patti J. Elzen
USDA, Honey Bee Unit, 2413 E. Highway 83, Weslaco, TX 78596, USA
William R. Rubink
USDA, Honey Bee Unit, 2413 E. Highway 83, Weslaco, TX 78596, USA
Abstract
The reproduction of pyrethroid-resistant Varroa destructor mite, a
brood parasite of honey bees, was observed in Weslaco, Texas, and the
results compared with known susceptible mite populations from other
studies. Seven Apis mellifera colonies that had mite populations
resistant to the acaricide Apistan* were used. Pyrethroid-resistance was
confirmed when only 17% rather than 90% of mites confined in dishes
containing Apistan* died after 12 h of exposure. The average number of
eggs laid by resistant mites invading worker and drone cells was 4.4 and
5.4 respectively. This is similar to the number of eggs laid by
susceptible mites in worker (4.4-4.8) or drone (4.7-5.5) cells. Also the
average number of fertilised V. destructor female mites produced by
resistant mites in worker (1.0) and drone (2.1) cells were similar to
the number produced by susceptible mites in worker (0.9) and drone
(1.9-2.2) cells. In addition, no major differences between the resistant
and susceptible mite populations were observed in either worker or drone
cells when six different reproductive categories and offspring mortality
rates were compared. Therefore, it appears that there is little or no
reproductive fitness cost associated with pyrethroid resistance in V.
destructor in Texas.
Decline in the proportion of mites resistant to fluvalinate in a
population of Varroa destructor not treated with pyrethroids
Norberto Milani and Giorgio Della Vedova
Università di Udine, Dipartamento di Biologia applicata alla Difesa
delle Piante, Via delle Scienze 208, 33100 Udine, Italy (Received 17
January 2002; revised 7 April 2002; accepted 15 April 2002)
Abstract
The reversion of resistance to pyrethroids in Varroa destructor
Anderson & Trueman was studied in Friuli (northern Italy), where
resistance was detected in 1995 and pyrethroids had not been used since.
Mites were sampled in seven localities each year between 1997 and 2000
and assayed in the laboratory for the resistance to f
luvalinate by using
paraffin coated capsules. Survival at the diagnostic concentration,
expected to kill all susceptible mites (200 mg/kg), decreased in all the
localities by about ten times in three years, from 19-66% to 1.3-7.8%.
Thus, the disadvantage associated with the resistance to pyrethroids in
V. destructor is small, as usual when resistance is due to
monooxygenases. Its impact on the selection of resistant mites during
annual application of treatments is negligible; appreciable effects of
reversion can be expected only over many generations of the mite.
Key words: Varroa destructor / reversion / resistance / pyrethroids
Correspondence and reprints: Norberto Milani
e-mail: [log in to unmask]
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