Varroa mites are the single greatest threat to sustainable beekeeping in the Northeastern US, and across the world. Now, a novel genetic trait described by Dr. Greg Hunt (SARE LNC08-295 2008-2011) is Mite-Biting Behavior, the MBB trait is when the honeybees bite off one or more legs from a varroa mite, and the bitten mites will then bleed to death. This project measured MBB, and its relationship to mite counts, Winter survivorship and colony weight. If MBB can increase Winter survival, it will increase the sustainability of beekeeping by reducing replacement costs of dead bees. This project involved queen breeders, bee clubs and beekeepers in Pennsylvania,Ohio, Indiana, and West Virginis, as well as Penn State and Purdue universities and the extension service.
Overall, our results show that Purdue stocks selected for mite biting behavior (MBB) chew a higher percentage of the mites. This difference between the Purdue MBB colonies and Controls persisted through the Fall. Colony weight and overall mite population (inferred from daily drop rates), do not significantly differ between the Purdue Stock and the Controls.
A good discovery was when one member also took it upon himself to also perform the ‘alcohol wash’ method to determine the mite count, in addition the prescribed ‘sticky board’ method; these results correlated very well. Therefore, and alcohol wash would be a good method to add to any studies moving forward.
While statistically not significant, the differences in weight and mite load at certain times in the Fall is worthy of more exploration and a similar experiment with greater number of colonies and more consistent timing of the measurements might yield additional differences between the Purdue MBB bees and Controls. The erratic data can also be attributed to the vast differences of test dates, 8/18/17 to 11/15/17 between the 7 bee yards, and the interpretation of a ‘chewed mite’ on the sticky boards by the 7 different technicians.
Winter survival for the Purdue MBB bees was 50% vs. the Control of 36%, or a mortality rate of 50% vs. 74%.
Our farm business, AlwaysSummerHerbs.com, LLC, has 5 greenhouses and 1.5 acres of outside nursery production to produce specialty herbs which we sell regionally at farm markets and nationally on the Internet. Farming includes 4 bee yards, breeding queen bees, and honey production. Our project management and business experience made us well suited for understanding both the scientific, technical and business aspects of this project. To date, we have completed 4 SARE grants in 2011, 2012, and 2013, and 2015. Being trained in horticultural Integrated Pest Management IPM, it only seemed logical that these practices be extended to our bees. . With the IPM approach to beekeeping, we have eliminated harsh miticides in our colonies, using soft treatments in hive when necessary, when mite counts exceed 3%. One of the pillars of IPM is resistant culitivars/genetics, which is why we using MBB bees seemed to be the next step. On our farm, IPM has reduced chemical cost, lower exposure to farm workers, improved health and productivity in the hive.
This project evaluated the relationship between MBB levels and the total number of Varroa mites, colony weight, and Winter Survivorship. MBB is a recently described grooming behavior trait that has been documented at high levels in some honeybee stocks, but it has yet to be proven as effective and practical tool for controlling/reducing Varroa mite populations, and improved Winter survival.
We compared a test group of MBB selected stocks versus a control group of commercially available stock of unselected bees obtained from a California breeder. The objective is, if MBB proves to reduce mite populations, we can select for this genetic trait in our breeding programs.
The study was completed in Pennsylvania, West Virginia, Ohio, and Indiana, and, and being conducted by participants from the Heartland Honey Bee Breeders Coop (HHBBC). We made 126 measurements for MBB% in 55 colonies in 7 different beeyards.
Our objective was to measure the relationship between mite-biting behavior (MBB) and the total mite count in honeybee colonies. MBB is a new and novel grooming behavior, and is defined by a honeybee biting one or more legs off of a Varroa mite. This will yield measurable results, and a potential tool for breeding selections. An assay has been developed by Dr. Greg Hunt at Purdue University (Hunt & Andino ABJ 2011) for accurately measuring the proportion of chewed mites in a colony. The method had two major components, collection of mites, and evaluation of chewed legs. We collected of mites in the field: (1) inserting an oiled board is inserted over the bottom board (floor) of the colony, (2) the board is allowed to remain for 24-48 hours, (3) the mite boards are removed from the colonies, and brought to safe processing area/lab. And then the second component is evaluation: (4) we sifted through the contents and plucked out the dark mature mites, (5) glued/set the mites “legs up” on a glass microscope slide/petri dish, and counted the total number, (6) viewed each mite on the slide under a low power microscope/15X-handlense and counted how many mites have chewed/missing legs, (7) calculated the MBB, as a percentage, example: 12 chewed mite/ 36 total = 33% . The collection portion was simple for beekeepers to collect in field with minimal training and tools. The evaluation component, steps 4-7, was more skilled, labor intensive and time consuming. There are two groups that were compared: 1) HHBBC-overwintered best MBB queens 2015 SARE grant, and 2016 AI queens inseminated with best MBB 2016 stocks raised in Purdue (2) Control Group-queens obtained from commercial queen producer in California, which were not been selected for any traits. These studies will allowed us to determine if the MBB traits is associated with reduced mite loads and overwintering success, and if breeding for the MBB trait is feasible. The beeyards locations planned to be in the HHBBC members respective states: Jeff Berta W-PA, Mark Gingrich E-PA, Bernie Svidergol C-PA, Dan O’Hanlon WV, Dwight Wells W-OH, Joe Kovaleski E-OH and Matt Evans IN. Each yard had started with 4 queens/colonies from each group, although some colonies failed to start for typical reasons.
The field data has been compiled into an excel spreadsheet, and currently undergoing statistical analysis. Note, the data germane to this report are listed as groups 1 and 2, other group numbers are part of the HHBBC stock evaluations. See excel sheet attached. Data-SARE-2016-Mite-Count-rev05.5formated
We performed a mixed model, repeated measures analysis to investigate the effects of queen background (i.e. Purdue Stock or Control) and time (measurements were repeated up to 3 times per colony) on mite drop rate (assessed through sticky board technique), mite biting rate (calculated as the percentage of mites within the drop that have been damaged by the worker bees), and colony weight (Mehmet Ali Doke PSU 2017). Excerpt of the Doke report follows:
“We found that mite biting rate was consistently higher within the Purdue Stock compared to Controls (p=0.0181) and there was no significant change in the biting rate within each stock through time (see Figure 1). Figure-1-Statistic
“Mite drop rate was not significantly different between the stocks (see Figure 2). However, there was a significant time effect (p=0.0157) on drop rate. A closer inspection of Figure 2 implies that mite drop rate might differ between the stocks at Time 1 (earliest recording for each colony, mostly taken in mid-September). However, even though the mean numbers for the stocks (22.6 mites/day for Purdue and 31.9 for Control), a limited comparison of the mite drop rate of the stocks at Time 1 does not yield in statistically significant difference between the two (p=0.32) likely due to the large variation in the drop rate (SD= 26.5 mites/day for Purdue and 36.0 mites/day for Control). Figure-2-Statistic
“Colony weight was also not significantly different between the stocks (see Figure 3). Again, there was a significant time effect on colony weight (p<0.001), which is expected as these colonies were going through Fall where they hoard resources for Winter. A closer inspection of Figure 3 shows that particularly in the Control colonies, the average weight increased between Time 2 and Time 3, creating a considerable weight gap between the two stocks at Time 3 (latest recording for each colony, taken mostly in mid-November). In this instance too, regardless of the mean weights for the stocks (71.0 kg for Purdue and 95.1 for Control), a limited comparison of the mite drop rate of the stocks at Time 1 does not yield in statistically significant difference between the two (p=0.13) likely due to the large variation in the drop rate (SD= 38.9 kg for Purdue and 32.6 kg for Control). Figure-3-Statistic
“Overall, our results show that Purdue stocks selected for mite biting behavior (MBB) damage a larger percentage of the mites within the colony as shown by the rate of biting behavior in the sticky board tests. This difference between the MBB colonies and Controls seems to persist through the Fall. Colony weight and overall mite population (inferred from daily drop rates), do not significantly differ between the Purdue Stock and the Controls.
The erratic data can also be attributed to the vast differences of test dates, 8/18/17 to 11/15/17 between the 7 bee yards, and the interpretation of a ‘chewed mite’ on the sticky boards by the 7 different technicians.
Winter survival for the Purdue MBB bees was 50% vs. the Control of 36%, or a mortality rate of 50% vs. 74%. Table 1 SARE-Winter-Survivorship-2017
While statistically not significant, the differences in weight and mite load at certain times in the Fall is worthy of more exploration and a similar experiment with greater number of colonies and more consistent timing of the measurements might yield additional differences between the Purdue MBB bees and Controls.
The study was completed in Pennsylvania, West Virginia, Ohio, and Indiana, and, and being conducted by participants from the Heartland Honey Bee Breeders Coop (HHBBC). The one fact that is most noticable is that the Purdue MBB bees do chew mites. The amount of chewing seems to be related to many factors such as: total mite load, honey flow, temperatures, time of year, overall health and colony size, to name a few. We are only beginning to understand chewing behavior, and the more we see, the more questions it raises. But it is clear that more work needs to be done with these groundbreaking genetics.
Education & Outreach Activities and Participation Summary
This project had a substantial amount of outreach as part of the PA Queen Improvement Project. We had 2 field days held on Saturday, June 18, 2016, one at Meadow View Beekeeping, LLC in Bethel, PA, and the other at Vorisek’s Backyard Beefarm in Linesville, PA.
In all, there were in excess of 130 people that attended the events. There were 10 county clubs represented, many by their club’s presidents. Over 130 MBB Purdue queen cells, and virgin queens and countless grafts were distributed to the attendees. The Meadeville Tribune covered the event and published and article on June 19, 2016. Allied-News-8AUG-2016
Ohio also participated on July 9, 2016 in Findlay, OH. It was organized by Dwight Wells of HHBBC, 6 clubs participated in the event, and about 90 queen cells were grafted. The skills of queen cell grafting and nuc creation was taught to the participants.
At the PSBA State Picnic we held a queen exchange for mated queens, an estimated 35 queens changed hands on Aug 6, 2016.
During the annual PSBA meeting on November 11, 2016 and the Pennsylvania Queen Improvement Project held and update meeting for all the bee clubs regarding the status of MBB genetics. Much interest and excitement about the past and future field day events for distribution of MBB genetics.
Beekeepers learned about making increase colonies (splits or nucs), queen introduction, queen rearing and mating. Also, learned about IPM by monitoring mite/parasite loads using sticky boards and looking for evidence of mite-biting on those sticky boards. They report that they have started to pay attention to the bees defending themselves against mites and how to measure that with a magnifier.
The two collaborators are the farm apprentices, Dolly Neely, and Tom Gaul and both changed their way of measuring parasites. The 7 beekeepers, including myself, have evolved and changed our methods during the extent of this study.
We received a $15,000 grant to work on feral bees.
The most notable outcome is that people are now aware that bees can defend themselves against the varroa mite parasite by chewing. Now people are looking to see if their bees are exihibiting this behavior; they have become “backyard scientists.” It was overhaerd at he field day, “This is a very exciting time in beekeeping now that the bees are fighting back trying to protect themselves” was the battle cry heard at the Linesville field day by an unnamed beekeeper. Or “I hope these new Purdue leg-chewers can save our bees from dying”.
Overall the project participants were eager to be a part of this program and have some of the latest and greatest genetics from Dr. Hunt’s “leg chewers” or “ankle biters” bees. The enthusiasm at time was contagious. During the 3 outreach events over 130 attendees listened to experts about the new breed bees and how to get them, and work with them. They learned about making increase colonies (splits) and installing new queens, and queen mating. They were also instructed on how to measure mite loads using IPM methods, and looking for ‘chewed mites’ as evidence of this new breed of bee. They all realized that they are now backyard scientists!
Our data set was large, over many states and spanned perhaps too long of period of time. We noted that chewing behavior was influenced by weather and honeyflows, and many other factors. Our statistician noted when one person collected his samples early in August, they did not compare to someone who collected them in November.
We used 7 bee yards, and the interpretation of a ‘chewed mite’ on the sticky boards by the 7 different technicians, also contributed some noise in the results. It would be optimum if everyone collect the samples on the exact same dates, and only one technician interpretted ‘chewed mites’ on the sticky board.
One member also took it upon himself (M. Gingrich in York PA) to also perform the ‘alcohol wash’ method to determine the mite count, in addition the prescribed ‘sticky board’ method; these results correlated very well. Therefore, and alcohol wash would be a good method to add to any studies moving forward.
Winter survival for the Purdue MBB bees was 50% vs. the Control of 36%, or a mortality rate of 50% vs. 74%. This overwintering data could have been better if we used mite treatments in the hives when they were over the IPM threshold of 3%. But treatment was not allowed in this study.
Our HHBBC members are excited to see, at least subjectively, that we are making improvements to our overall vigor of our bees, even though the reported statistics are not conclusive.