> The question that beekeepers have been asking: is there any similar miticides with different modes of actions in the tool box or in the pipeline to replace those failing ones due to resistance?

Hi all
Medhat knows as much or more about this than I do, but here's a little background info on the topic. Wolfgang Ritter wrote in 1981

[quoted for educational purposes]

Any new method of control should be tested in the country of intended use. This
cannot be done before Varroa is in the country, but it can then be done in a short space
of time and without great expense, as the following example in Turkey shows.

Varroa was first diagnosed in Turkey in 1976-77. There is much migratory
beekeeping there, especially by the commercial beekeepers, and 200 000 colonies are
concentrated together in the Izmir-Antalya region for the honeydew flow each year.
These factors led to a rapid spread of Varroa over a wide area.

Comparative tests were made with drugs already tested in the German Federal Republic.

Treatment with a 1-5% kelthane suspension killed on average only 30% of the mites.

The average proportion of mites killed after 4 g of the fumigant phenothiazine was
burned and the smoke directed into the entrance of each hive was only 30%, but after
a single treatment with 2 strips of Folbex it was 70%.

The highest success rate was obtained from the evaporation of 98% formic acid. The
bottles were placed either near or above the brood nest. When about 20 ml
evaporated daily, the average proportion of mites killed was 74% in 2 days.

A danger lies in the uncontrolled use of chemical agents for treatment. In
most countries the choice of agent, and the time and frequency of application, are left
entirely to the beekeeper. Unsuitable, highly toxic substances are coming into use
which, if used improperly or at the wrong time, contaminate the honey. Frequent
underdosing will give rise to resistant strains of mite; this has already been observed
with phenothiazine in Japan, where 32% of beekeepers treat their colonies up to 6
times throughout the year

Ritter, W. (1981). Varroa disease of the honeybee Apis mellifera. Bee world, 62(4), 141-153.

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