The effects of temperature and dose of formic acid on treatment efficacy
against Varroa destructor (Acari: Varroidae), a parasite of Apis
mellifera (Hymenoptera: Apidae)

Robyn M. Underwood
Department of Entomology, University of Manitoba, Winnipeg, Manitoba,
R3T 2N2, Canada (e-mail: [log in to unmask])


Robert W. Currie
Department of Entomology, University of Manitoba, Winnipeg, Manitoba,
R3T 2N2, Canada

Abstract

In order to decrease the variability of formic acid treatments against
the honey bee parasite the varroa mite, Varroa destructor, it is
necessary to determine the dose-time combination that best controls
mites without harming bees. The concentration × time (CT) product is a
valuable tool for studying fumigants and how they might perform under
various environmental conditions. This laboratory study is an assessment
of the efficacy of formic acid against the varroa mite under a range of
formic acid concentrations and temperatures. The objectives are 1) to
determine the effect of temperature and dose of formic acid on worker
honey bee and varroa mite survival, 2) to determine the CT50 products
for both honey bees and varroa mites and 3) to determine the best
temperature and dose to optimize selectivity of formic acid treatment
for control of varroa mites. Worker honey bees and varroa mites were
fumigated at 0, 0.01, 0.02, 0.04, 0.08, and 0.16 mg/L at 5, 15, 25, and
35 °C for 12 d. Mite and bee mortality were assessed at regular
intervals. Both mite and bee survival were affected by formic acid dose.
Doses of 0.08 and 0.16 mg/L were effective at killing mites at all
temperatures tested above 5 °C. There was a significant interaction
between temperature, dose, and species for the CT50 product. The
difference between the CT50 product of bees and mites was significant at
only a few temperature-dose combinations. CT product values showed that
at most temperatures the greatest fumigation efficiency occurred at
lower doses of formic acid. However, the best fumigation efficiency and
selectivity combination for treatments occurred at a dose of 0.16 mg/L
when the temperature was 35 °C.


.....................................................
Adony Melathopoulos, M.P.M.
Apiculture Biotechnician / Biotechnicien en Apiculture
Agriculture and Agri-Food Canada / Agriculture et Agroalimentaire
Canada
Telephone / Téléphone: 780-354-5130
Facsimile / Télécopieur:  780-354-8171
P.O. Box 29 / C.P. 29
Beaverlodge,  Alberta / Beaverlodge (Alberta)
T0H 0C0   Canada
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