Hopguard is a varroa miticide that came out a few years ago (2011?). The active ingredient is “hop beta acids”, which are derived from hop flowers – more commonly known as a flavoring for beer. Hopguard is marketed as a natural miticide, which it is. It can be used even with honey supers on the hive, though not inside the supers. As a contact miticide, as opposed to a fumigant, it can be used without regard to outside air temperatures. The strips are made of cardboard and are saturated with hop acid, so they are wet and brown in color when removed from the packaging. The product does kill mites, and beekeepers tell me that it does not affect the bees negatively in any way. (I haven’t used it myself.) They also tell me that the strips dry out and are ineffective after a few days, so the percentage of mites killed with a single treatment is not high. The Hopguard label states that it can be used up to three times a year, and the beekeepers who seem happiest with their results are those who use three consecutive applications, each a week apart. The efficacy also improves if the hives are broodless, in early spring or late fall. Hopguard only kills mites on the bees; it does not kill varroa on the larvae in the capped brood. It currently carries what is called a section 18 label, and may not be available for purchase by beekeepers in every state.
I wish to make clear that I have no direct experience with Hopguard, and am not aware of any research evaluating the effectiveness of consecutive applications. I’m just reporting what beekeepers are telling me. Before using any treatment, you should always monitor to determine varroa levels and decide whether treatment is necessary. Afterwards, you should monitor again to assess how effective it was.
I’m hearing that the makers of Hopguard are making some alterations to the product, hoping to increase its efficacy. The cardboard material used in the strips is to be changed so that the strips do not dry out as quickly, and the strength of the active ingredient is to be increased. Be aware that to make these changes and sell the new strips, they will have to change the registration on a state by state basis – a time consuming process fraught with red tape. If you have heard about these changes and intend to purchase Hopguard, do not assume that you will be getting an updated product. Ask your dealer which version you are buying.
See my “Ask Phil” Question & Answer column each month in Bee Culture Magazine