I used Hopguard before I went to OAV, as I understand it they have changed it a bit? When I treated with hopguard I had to run three treatments, or a years worth through the hives all at once to get a good mite kill...
Man dont get that stuff in your eye it burns like someone stuck a hot poker in there.
Part of my reason for going OAV is because I could never seem to keep from getting that stuff everywhere... I would think I was good until I went to take off gloves, or suit, or hood etc... usually I found it about the time I smeared it all over myself... The other reason was because of how the bees reacted to it... Hopguard dosnt seem to affect queens, drones or workers in any way, except that it smells bad enough that it has them bearding when first installed... after that they seem to get used to it, and will even tear up the strips and haul them out.