In the 1990s, the Bee Research Centre took part in a screening programme testing the potential effectiveness of over 100 essential oils and essential oil components against the varroa mite. Although sage, hyssop and thyme oils proved interesting, only thymol has been used in acaricide products. Thymol treatments require little effort, and there are a variety of preparations on the market. The advantages and drawbacks of thymol use are listed in the articles "Apilife VAR: A new varroacide with thymol as the main ingredient" and "THYMOVAR for Varroa control".
The Asian chestnut gall wasp (Dryocosmus kuriphilus Yasumatsu, Hymenoptera, Cynipidae) is considered as one of the most dangerous pests of the genus Castanea. In southern Switzerland repeated heavy Asian chestnut gall wasp attacks prevented chestnut trees from vegetating normally for years before the arrival and spread of the biological control agent Torymus sinensis Kamijo (Hymenoptera, Torymidae). This resulted in a greatly reduced green biomass and flower production. In this paper, we analyse the impact of such an ecosystem alteration of the environment on the composition of produced honey. Six beekeepers were chosen from sites with different densities of chestnut trees, each of which providing series of honey samples from 2010 to 2016. We determined the chestnut component in the honeys via a combined chemical and sensory approach, and correlated the obtained results with the degree of yearly Asian chestnut gall wasp-induced crown damage and weather conditions during the period in question in the surrounding chestnut stands. The chestnut component in the analysed honey sample series showed a strong correlation with the degree of Asian chestnut gall wasp-induced crown damage, whereas meteorological conditions of the corresponding year had a very marginal effect. Decreases in the chestnut component of the honey were statistically significant starting from a Asian chestnut gall wasp infestation level of 30%.
Although the use of thymol leads to residues in the wax and honey, these are negligible from a toxicological viewpoint. Since about 2008 the use of thymol-based products has been declining in Switzerland, and beekeepers making use of these products have tended to experience greater winter losses than those using e.g. formic acid.