Treatment against varroatosis using compounds of essential oils

Essential oils have been reported to have some effects on the behavior of Varroa jacobsoni: attracting, repelling or intoxicating the mites. Only few compounds are considered to have an efficiency high enough to be used in bee hives against varroatosis. Our communication reports on the efficiency of a product consisting of thymol (74.1 %, w/w), eucalyptol (16.0%), menthol (3.7%), camphor (3.7%) and vermiculit (2.5%, carrier substance). We established by means of GC/MS, GC-NPD and GC-ECD-analysis, that no other acaricides were present. The pellets, obtained on the market under the name "Apilife/VAR"+) were placed above the brood on the combs in Swiss hives (side-opening). They were exchanged for new pellets after two weeks. The second set of pellets was left in 20 bee colonies for 24 days, in 20 colonies of a second apiary for 65 days. In the first case the treatment ended at the 21 st of September, in the second case at the 21 st of October 1990. The mites on the hive floor were counted once or twice a week. In December/ January all colonies had 2 control-treatments using Perizin to measure the remaining population of Varroa jacobsoni. Figure 1 shows the respective numbers of mites per day and colony on the hive floor before, during and after the two treatments. Table I is a summary of the total amount of mites during the treatments with "ApilifeNAR" as well during the two control treatments with Perizin. The tests showed a mean efficiency of the oils of 96.4% for the shorter treatment and 99.0% for the longer duration. Efficiencies like the above found are comparable to those found in treatments using synthetic pyrethroids (Koeniger and Fuchs, 1988). The following questions remain to be solved, before we recommend "Apilife/Var" for general use in varroatosis control: 1. Is the efficiency consistent? Repetitions of the tests in 1991 will show it. 2. What about residues? 3. What mode of action - repellent or toxic - is involved