Effects of treatments with Apivar & Thymovar on V. destructor populations & virus infections, Canada

Efficacies of two miticides, Apivar
and Thymovar
, were evaluated as a fall treatment against V. destructor. The effect
of treatment with miticides was further evaluated by monitoring both viral load and rate of indoor overwintering
survival of colonies of European honey bees (Apis mellifera L.) in the vicinity of Saskatoon, Saskatchewan, Canada.
Forty-five colonies were randomly assigned to three treatment groups with 15 hives per group: Group 1; 2 strips of
Thymovar
(thymol); Group 2; 2 strips of Apivar
(Amitraz); and Group 3; no treatment (control). Significant
decreases in the rates of colony infestation (Mites per hundred bees, MPHB) by V. destructor were observed (p < 0.05)
between colonies of bees treated with Apivar
in October 2013 when compared to control colonies. Efficacy of
Apivar
and Thymovar
against V. destructor after treatment for 22 days were 76.5 and 26.7%, respectively. After
22 days, concentrations of the two miticides in bees were 15.4 ng amitraz/g wet mass (wm) and 64,800 ng thymol/g
wm. There were no significant differences (p > 0.05) in the percentage of colonies infected by deformed wing virus
(DWV) and Israeli acute paralysis virus (IAPV) either before or after treatment with Apivar
or Thymovar
in
October 2013 and 7 months post treatment in April 2014. Only the Apivar
treatment group showed IAPV infections
in April 2014. The group treated with Apivar
exhibited a better overwintering rate of survival (93%), than hives
treated with Thymovar
(67%). These results suggest volatile miticides like Thymovar
should be avoided in
geographical areas with colder fall temperatures.

Yahya Al Naggar, Yang Tan, Colton Rutherford, Wayne Connor, Philip
Griebel, John P. Giesy & Albert J. Robertson (2016): Effects of treatments with Apivar®
and Thymovar® on V. destructor populations, virus infections and indoor winter survival
of Canadian honey bee (Apis mellifera L.) colonies, Journal of Apicultural Research, DOI:
10.1080/00218839.2016.1186917