I'm posting something I've written from my personal view, and I hope you guys like it.
Hopguard is a relative new product on the market to treat bees for varroa mites. It can be used with honey supers on the hive, but should not be used over honey super frames. It is not temperature dependent, which makes it ideal for those living in colder climates. Ideally you treat in spring and in fall, but you can add a summer treatment, if needed.
It's plus side is that it is of a food grade product, meaning you do not need to wear a respirator or have to take other major precautions when using and handling it. This product is present and added to human foods making it technically 100% organic, but it has not been registered as is. It consists of paper strips soaked in a hops based product called potassium salt of hop beta acids. Recommended personal protection is eye wear and plastic gloves. You do not want this to get into your eyes, and the gloves keeps the sticky mess off your hands.
Hopguard does not get the mites in the closed brood cells so a 3 week treatment is needed. Normally you use 2 strips for each deep brood box placed in opposite sites over the 3rd and 6th frame alone. You don't remove it and let the bees clean it up. I've observed that strips appear dry and half of them have been dismantled by the bees after only one week. There was almost nothing left in my strongest hive. This may differ from region to region, and perhaps depends on the temperature or regional climate when applied. Because of this it may be a good idea to use the progressive treatment option. Most mites dropped in the first 24 hours.
In the progressive treatment you replace the strips every week over 3 weeks to have the best treatment effect. One noted side effect is that the queen may slow down in her laying, but usually never stops completely with this treatment option. The progressive treatment option does make it a little bit more expensive then some of the other treatments out there. It's ease of use makes it worse while. I've noted that bees remain calm while using and replacing Hopguard strips.
Interestingly I've noticed dead red and black ants on the bottom board while using Hopguard. Sprinkling cinnamon seems to deter the sugar ants, but does not have equal effect on the larger black and red ants that rob the bees of their honey and pollen stores.
Preliminary reports also show a positive effect on treating American and European foul brood, and even chalk brood with Hopguard. It is promising but further studies are needed. Never the less BetaTec is working on a patent for the Foulbrood usage.