The use of hop products for organic control of varroa (Varroa destructor)




01. October 2016 - 30. September 2019


Stanko Srčič


4.04.03 Biotechnical sciences / Veterinarian medicine / Therapy and health prevention of animals

Research Organisation:







In Slovenia there are currently 11.000 beekeepers, which own and maintain 150.000 bee colonies annually producing 2.000 t of honey and other bee products. Thus, they represent a very important economic share in agriculture. In the beekeeping sector in recent years, a tendency of increased use of organic products for varroa control, i.e. those that are acceptable to the colony and ensure the integrity of bee products is present. Currently, the prevailing treatments are with preparations based on formic and oxalic acid. The latter is intended primarily for winter varroa repression. One is also known as the combination of both. At the same time there are some preparations known and registered for organic repression on the base of plant extracts. When using any product it is necessary to take particular care on the side toxic effects on bee family. Special attention requires an examination of the possibility of penetration of active ingredients into honey and other bee products, which is not allowed, particularly where such substances pose a risk to humans. Recently, on foreign markets began to appear preparations based on hop beta-acids, which are offered as an alternative, since they are perceived as harmless, naturally occurring in the environment and consequently their maximum residue limits (MRLs) are set as not relevant. An important industry in Slovenian agriculture is also hop growing, which annually produce 2,500 t of hops and hop products, which ranks Slovenia in the fifth place in the world with 3% of world production. The problem in the hop growing is that 95% of all is consumed for brewing purposes. Consequently hop industry is always looking for alternative uses for hops outside the brewing industry. In addition to the role of the hops in beer as a raw material, which gives beer flavor and aroma, it’s very important role is also the role of a preservative, because beer is one of the few drinks where there are no preservatives added. The protective role in this case play hop beta-acids that have a proven antimicrobial effect. The project offers the synergy between the two sectors and their needs. We will examine the situation of products for organic suppression offers on the market and prepare a comparison of the mode of their application and effectiveness. In the project we will carry out practical testing of hops extracts in the form of toxicity tests of hop extracts on varroa with 1) various extracts, 2) at different concentrations and 3) with the different methods of application. The tests of hop extracts to the bees will be compared 1) by different concentrations, 2) various extracts and 3) in different ways of applications. Toxicity tests will be tested also in the variant of bees infested with varroa. We will review oral toxicity to bees and evaluate the effects of hop extracts on the scrub behavior of bees. In continuation of this working package we will carry out a pilot trial by carrying out tests on families where also observing of all the environmental factors that may affect the condition of the family will be maintained. After conducting a pilot experiment, sensory evaluation of honey will be performed in order to determine the possible transition of hop components in honey, and possible impact to sensorial properties. The completion of this work package will be a prototype product based on beta-acids on which stability tests in laboratory environment will be conducted. From existing gene banks of standard varieties and collections of new hop breeding lines we will search for suitable hop genotypes. We will determine the content of alpha- and beta-acids, and the quantity and composition of essential oils. Based on the results we will create a list of prospective genotypes suitable for cultivation for the purpose of extracting beta-acids. In commercially available hop extracts we will determine their chemical composition of hop resins and essential oils, as a potential disruptive element. 



Bibliographical references, arising directly from the implementation of the project:


Financed by:

Research projects (co)funded by the Slovenian Research Agency.