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All hives received OA treatment at the end of November (when colonies were brood less) to determine nite population after the treatments. The result was plotted against average daily mite drop (prior the reatment) and showed a strong correlation (y=123x with R’=0,9546, where y = total population of mites and x is daily mite drop), se Fig 9. The result supports that in November the mite drop can be used to udge the total population and thus judge if an additional treatment is needed. The result from this study confirms other researchers’ results that a linear correlation exists (Brodsgaard, C.J, Brodsgaard, H.F., 1996). (Genersch et al, 2010) found that the threshold infestation level was 6 % to keep the winter losses selow 10%, which gives 600 mites as max allowed winter population, if only strong colonies with ninimum 10000 bees are considered to winter in. Smaller colonies than 10000 bees increase the risk of winter losses (Jeffree, E, 1956, Genersch et al, 2010). The results support that mite drops of < 3 mites yer day (correlating to about 400 mites) can be tolerated in brood less colonies without any further 1utumn treatment, marked in the graph with green lines. Fig 9. Correlation between total mite drop after OA treatment and daily average mite drop prior the treatment.

Figure 9 All hives received OA treatment at the end of November (when colonies were brood less) to determine nite population after the treatments. The result was plotted against average daily mite drop (prior the reatment) and showed a strong correlation (y=123x with R’=0,9546, where y = total population of mites and x is daily mite drop), se Fig 9. The result supports that in November the mite drop can be used to udge the total population and thus judge if an additional treatment is needed. The result from this study confirms other researchers’ results that a linear correlation exists (Brodsgaard, C.J, Brodsgaard, H.F., 1996). (Genersch et al, 2010) found that the threshold infestation level was 6 % to keep the winter losses selow 10%, which gives 600 mites as max allowed winter population, if only strong colonies with ninimum 10000 bees are considered to winter in. Smaller colonies than 10000 bees increase the risk of winter losses (Jeffree, E, 1956, Genersch et al, 2010). The results support that mite drops of < 3 mites yer day (correlating to about 400 mites) can be tolerated in brood less colonies without any further 1utumn treatment, marked in the graph with green lines. Fig 9. Correlation between total mite drop after OA treatment and daily average mite drop prior the treatment.

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In total, 11 matched pairs and an additional 5 test hives were used. All hives received one three-way drone comb, (fig. 1), kept in the upper brood chamber placed next to the last worker brood comb. In the control group, drone combs were left in place throughout the season, but lifted and returned the same way as the test colonies to simulate the manipulation of the test colonies. The bees were left to use the drone combs in the test colonies as they pleased (for brood rearing or to store honey). Fig 1. Three-way drone comb where the middle division is capped and ready to be removed, the right division is partly capped and will be ready the coming week and the division to the left is filled with newly laid eggs.
In total, 11 matched pairs and an additional 5 test hives were used. All hives received one three-way drone comb, (fig. 1), kept in the upper brood chamber placed next to the last worker brood comb. In the control group, drone combs were left in place throughout the season, but lifted and returned the same way as the test colonies to simulate the manipulation of the test colonies. The bees were left to use the drone combs in the test colonies as they pleased (for brood rearing or to store honey). Fig 1. Three-way drone comb where the middle division is capped and ready to be removed, the right division is partly capped and will be ready the coming week and the division to the left is filled with newly laid eggs.
Fig 4. The graph shows the progression of mite drop counts; the start of the test with all colonies below 2 mite drop/day. The Control group showed big variances of the mite drop where especially two hives maintained high mite drop indicating that the FA was not very effective on these two hives. Two of the Control hives received no FA in August, a judgment call, due to low mite drop. They are plotted separately in light blue colour in October and November bars.
Fig 4. The graph shows the progression of mite drop counts; the start of the test with all colonies below 2 mite drop/day. The Control group showed big variances of the mite drop where especially two hives maintained high mite drop indicating that the FA was not very effective on these two hives. Two of the Control hives received no FA in August, a judgment call, due to low mite drop. They are plotted separately in light blue colour in October and November bars.
Fig 5. The graph shows the progression of mite drop counts for both Test and Control. The DBR supress the mite drop and with occasional LA applications the mite drop continued to be low during the whole season.
Fig 5. The graph shows the progression of mite drop counts for both Test and Control. The DBR supress the mite drop and with occasional LA applications the mite drop continued to be low during the whole season.
Fig 6. Estimated final mite populations per hive, based upon mite drop counts after oxalic treatment in all colonies. The difference is not significant, but the test colonies showed a lower variance than the control colonies where only 1 out of 10 test colonies had more than 400 mite drops whereas 2 out of 7 control hives had more than 400 mite drops after the oxalic acid treatment although it should most likely have been 3 out of 8. The Control hive with highest mite drop prior Oxalic acid (27,8 mites/ day) ended up in a storm that blow away all the mites after OA application and hence removed in this graph (n=7 for control).
Fig 6. Estimated final mite populations per hive, based upon mite drop counts after oxalic treatment in all colonies. The difference is not significant, but the test colonies showed a lower variance than the control colonies where only 1 out of 10 test colonies had more than 400 mite drops whereas 2 out of 7 control hives had more than 400 mite drops after the oxalic acid treatment although it should most likely have been 3 out of 8. The Control hive with highest mite drop prior Oxalic acid (27,8 mites/ day) ended up in a storm that blow away all the mites after OA application and hence removed in this graph (n=7 for control).
The mites have a high preference available drone cells then the mi to enter a drone cell (Fuchs 1992) but if there are more mites than es enter a worker cell rather than share the drone cell with another mite. More than one mite per drone cell will lower the fecundity and therefore it’s better optimization for the mite to infest a worker ce |. From the result we see that we have a max average infestation level of 15 % (the highest value was 40%) so the available drone cells appear to be enough to offer each ready mite a fresh drone cell. The trapped number of mites was stable the three first cutouts (average 40-60 mites/ cutout) and then it d ropped drastically from 4" cut and onwards, see Fig. 8. The daily Average mite drop decreased to close to zero which confirmed that the mite population had become very Taw Drone cells prevalence
The mites have a high preference available drone cells then the mi to enter a drone cell (Fuchs 1992) but if there are more mites than es enter a worker cell rather than share the drone cell with another mite. More than one mite per drone cell will lower the fecundity and therefore it’s better optimization for the mite to infest a worker ce |. From the result we see that we have a max average infestation level of 15 % (the highest value was 40%) so the available drone cells appear to be enough to offer each ready mite a fresh drone cell. The trapped number of mites was stable the three first cutouts (average 40-60 mites/ cutout) and then it d ropped drastically from 4" cut and onwards, see Fig. 8. The daily Average mite drop decreased to close to zero which confirmed that the mite population had become very Taw Drone cells prevalence
Fig 10. The table show, for information, a summary of all mites that have been removed from each colony. Colony KJ1-C1 didn’t report any result after OA treatment since a storm blow away the mites after the treatment. The colour in column 1 shows the apiary.
Fig 10. The table show, for information, a summary of all mites that have been removed from each colony. Colony KJ1-C1 didn’t report any result after OA treatment since a storm blow away the mites after the treatment. The colour in column 1 shows the apiary.
Fig 11. LAT where the combs are mowed sideways, instead of removing and spraying each comb individually, and the solution is sprayed between the combs. We have not noticed any difference in the efficiency, so the two methods appear to be equal. When the colonies were brood less, in late November/early December we found a positive straight-line correlation where the average daily mite drop x 124 would estimate the total population. The straight- line correlation confirms the result of other studies (Liebig,1983; Brodsgaard, C.J, Brodsgaard, H.F., 1996).
Fig 11. LAT where the combs are mowed sideways, instead of removing and spraying each comb individually, and the solution is sprayed between the combs. We have not noticed any difference in the efficiency, so the two methods appear to be equal. When the colonies were brood less, in late November/early December we found a positive straight-line correlation where the average daily mite drop x 124 would estimate the total population. The straight- line correlation confirms the result of other studies (Liebig,1983; Brodsgaard, C.J, Brodsgaard, H.F., 1996).
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