Jim Bach provided some information that was published in the July 1994 edition of Bee sCene, the publication of the British Columbia Honey Producers' Association (B.C. HPA). Perhaps he has published a more complete version of the test. If any one knows, I would appreciate hearing. I don't know how valid the method is, and he didn't include any actual correlation with field results. Kerry Clark, Apiculture Specialist B.C. Ministry of Agriculture 1201 103 Ave Dawson Creek B.C. V1G 4J2 CANADA Tel (604) 784-2225 fax (604) 784-2299 INTERNET [log in to unmask] He wrote (abbreviated): Recently I had some Apistan strips tested by the state chemical laboratory. The lab used alcohol swabs to remove available fluvalinate from the surface, then determined the amount of fluvalinate in the swabs. 3 samples of 10 strips: #1. new strips opened last fall. #2. strips used in treating colonies for 45 days: slightly travel stained #3. strips used in treating colonies for 45 days:: "more heavily travel stained: minimal propolis and wax particles" Results: #1 (new): 809 ug #2 201 ug 24.8 % of new #3 142 ug 17.6 % of new He concluded," These results may explain the observed ineffectiveness or reduced effectiveness of treatments in Florida and elsewhere when one new and one old strip is used to treat colonies for Varroa."