Winter? It seems like a long time before we think about winter but in reality it is not so far away IF we plan to do something about mites. NOW (end August/early September) is the proper time to sample colonies to determine risk level and make mite control decisions, if you wish to do so.
Why monitor? I have had a chance to look more closely at the loss surveys returned by 28 WVBA members. See report on website: http://pnwhoneybeesurvey.com/survey-results/2015-16-survey-reports/ . Using your survey returns I computed the loss rate of individuals as related to management activities reported by each individual on their survey returns.
Survey results: On the survey I asked ‘Did you use any control technique/method for mites?’ Eighteen WVBA individuals (64%) said they did employ a mite control, which was a 7 percentage point higher level compared to the 219 OR beekeepers in the full survey. The 18 TVBA individuals that said they did employ a control had a 30% loss while the 10 WVBA members who checked ‘No they did not do a control’ reported a 47% loss. For the larger database of 219 Oregon survey returners the difference was 32.7% winter loss or those who said they did mite control vs 67.4% loss for those who did not do any control, an incredible difference.
What works? On the survey I had two separate questions on mite cotnrols used, one for alterantive techniques and the second on chemcial tools. The 6 indiividuals (21%) who did not select any alternative had a 36% loss rate, same as average loss rate for the 28 WVBA respondents last year. The most popular alternative control used by WVBA respondents, screen bottom boards, indicated by 13 individuals, did not show an advantage, as these indivdiduals had a loss rate of 38%. The next most commonly selected alternatives, minimal hive interrvention likewise did not show an improvement, individuals who selected this alternative had a 40% loss rate.
Both WVBA & Oregon: For the larger data base of total OR beekeper response, 126 Oregon respondents who checked use of screen bottom board (including the 13 from WVBA) had a 35% loss rate average, nearly 8 percentage points better than the overall loss of 43.7%. Those Oregon individuals who said they used minimal hive intervention (42% of respondents that used an alternative) had, like the WVBA members, a higher than base loss rate, 54% loss. Among other alternative selections the 26 individuals (19%) who said they utilized small cell/natural comb had a loss rate of 56%. The 8 individuals who said they used an alternative hive had an even higher loss of 59%. Use of some alternatives however did show improved survivorship rates. The combinations of apiary configuration and apiary siting (42 individuals – 30%) had the best (lowest) winter loss – 18%. The 40 individuals doing the highly interventive manipulations of Drone brood removal and Brood interruption , 28 individuals, had a 27% loss rate.
Chemical control: It is in use of a chemical tool where the greatest differences were found in the WVBA member loss rate comparisons. Nine individuals did not use any of the chemicals; these individuals had a 47% overwinter loss. The 19 individuals who did use a chemical indicated use of 25 of the chemicals, thirteen of whom used only a single chemical, had a loss rate of 29%. The seven individuals who used Apiguard, 4 of which used this chemical alone,( 2 used it in combination with Oxalic and one used it with Formic acid), had a 31% loss, a slight improvement in survivorship over non-use of a chemical. The 9 individuals who used Apivar, 7 of which used only Apivar, had a 36% loss rate.
WVBA & Oregon: Use of a chemical control was most significant in improving winter survivorship for OR beekeepers. Apivar, the synthetic amitraz chemical, was used by 43 OR individuals, who had a much better survival rate with only a 23% loss rate. Twenty one individuals used ONLY Apivar, 15 used 2 chemical materials, 5 used 3 chemicals and 1 each used 4 & 5 chemicals. MAQS (Formic acid) was also very helpful for improving survivorship. MAQS was used by 42 individuals and they too had only a 23% loss rate. Among the 42 individuals, 17 used ONLY MAQS, 16 used 2 chemicals, 9 individuals used 3 and 1 each used 4 & 5 chemicals.
The essential oil Apiguard was used by 32 individuals; they had a 26% loss. 14 individuals used ONLY Apiguard, 10 used 2 chemicals, 7 used 3 and 1 used 5 chemicals. Oxalic acid was used by 30 individuals; they had a loss rate of 35%; 7 of these individuals used ONLY Oxalic acid, 15 used 2 chemicals, 7 used 3 and 1 used 4. Use of Powdered sugar also seemed to decrease loss. Powdered sugar was the chemical choice of 16 individuals; their loss rate was 29%. Of the 16 individuals, 7 used ONLY PS, 2 chemicals were used by 3 individuals and 4 used 5 chemicals.
Correlation not causation: The numbers here are what 28 WVBA/219 OR beekeepers, your neighboring beekeepers, said they did and what kind of survival rate they had overwinter. They are a correlation – if x was used/done those individuals had an XX loss. They do NOT mean if you did/used the same, your loss rate would be higher or lower – doing/using XX doesn’t mean it may cause your loss rate to be higher or lower. Non-treatment may be by default, a decision based on sampling results or beekeeper philosophy. While it appears that some treatments/chemicals, even those that are less effective, improves colony winter survivability not all beekeepers use survivorship as a measure of beekeeping success. For those who may wish to reduce winter losses, the survey results, what your beekeeping neighbors are doing, do provide a snapshot of what some did to reduce winter loss /improve survivorship last season.