I have always found Mann Lake to be very good. However, Varroa treatment strips from many sources have a notoriously short expiration date. I think it is one of two things, or maybe both:
- CYA (cover your @$$) policy by the manufacturer. They want you to use it while it is as potent as possible, but the dates are probably a lot shorter than absolutely necessary.
- Drive the customer to buy more often and throw out perfectly good older product. Aka revenue generation
I don’t think it is Mann Lake’s fault, but I do think it is a conspiracy by the treatment industry.
Lovely can of worms, that one! You have had some great answers from @Red_Hot_Chilipepper (Ed) and @Eva. I try very hard not to use chemicals in my hives, but there are chemicals and there are sort of chemicals. I prefer to use oxalic acid (OA), but like Ed, if I have treated and the mites cause problems again within a month or two, I will consider Apivar strips.
There is some benefit to rotating treatments to avoid resistance, although there is no evidence that it is possible for mites to become resistant to OA (and bee researchers have looked hard at this).
There is a very good booklet which gives all the pros, cons and effectiveness of various treatments. I think they are behind the times with their comments on OA vapor, but otherwise it is very helpful:
It is good that you are thinking about it already. There is nothing more demoralizing than losing a hive because you failed to treat in time.