Sustainable parasitic mite control for honeybees

“Two changes in beekeeper behavior are targeted: 1) 500-1000 beekeepers will be monitoring varroa levels to determine if a threshold has been exceeded prior to treating the colony with a miticide and 2) 100 beekeepers will have implement at least IPM tactics to control varroa.”
“This project targets 300 of the approximately 5000 hobbyists and 700 sideliners in MAAREC to participate in planning workshops. From the 300 beekeepers, 10 beekeepers will participate in the evaluation of IPM tactics plus mite monitoring. Each of the beekeepers will hold, with our assistance, a workshop at his/her apiary to demonstrate IPM tactics and monitoring. Fifty beekeepers will attend each apiary workshops (400-500 total) and 40-80 will implement multiple IPM tactics to control varroa during the second year. Few beekeepers currently monitor for varroa and IPM cannot be implemented effectively without monitoring; we will encourage beekeepers to begin monitoring for varroa. Approximately 200 beekeepers each year will be recruited to begin monitoring.”

Target One: “500-1000 beekeepers will be monitoring varroa levels to determine if a threshold has been exceeded prior to treating the colony with a miticide.”
Each year surveys were distributed via the U.S. mail using State Beekeeper Association mailing lists or through the State Apiary Inspection Program. Additionally, surveys were distributed at beekeeper meetings. Notices were placed in various beekeeper newsletter to encourage beekeepers to complete yearly surveys using either the hard copies that were distributed or electronic copy on the MAAREC web site. Unfortunately, the response rate was extremely poor throughout the study period. To supplement the information we were able to glean from the surveys that were returned, information was obtained from the apiary inspection program in Pennsylvania (where the return rate was the lowest). Information was also obtained by directly questioning beekeepers attending workshops and meetings. All information we have to evaluate whether or not we achieved our objectives is anecdotal and not necessarily reliable.
The apiary inspectors during the three years of the project were instructed to demonstrate mite monitoring techniques. In the group of beekeepers who were inspected a second time during the project’s duration (inspections are biannual) inspectors found that greater than 50% of beekeepers report that they check the mite levels in their colonies at least once per year, usually in August or September. At least 25% are monitoring for mites more than once.
Initially our recruitment efforts to get beekeepers to monitor for mites were disappointing. We discovered that we could increase the participation rate by requesting that the beekeepers send the results of the monitoring to us for inclusion in an evaluating of the efficacy of the suggested mite threshold. As a result we were able to obtain the participation of over 100 beekeepers each year, thus attaining our target. The data collected from the beekeepers has been of limited use because of the lack of consistency in the data. Some beekeepers reported mite number but not colony survivorship information or the linkage between the mite numbers in a colony and colony survivorship was questionable.
We achieved our goal for this target. The beekeeper who responded to the surveys indicate that more than 80% of beekeepers are monitoring their colonies for varroa mites. Even if it is assumed that the survey over-states monitoring behavior, we met our goal of 500-1000 monitoring for varroa mites. If only 25% of beekeepers are monitoring for mites in the MAAREC region over 1,400 beekeepers are tracking mite levels in their colonies.
Target Two: “100 beekeepers will have implemented at least two IPM tactics to control varroa.”
For the same reason described above, the information we have concerning whether or not we achieve our goal of 100 beekeepers implementing at least two IPM tactics to control varroa is anecdotal.
At this time over 50% of beekeepers have implemented at least one IPM control tactic. The most common method has been screened bottoms. There is a substantial amount of misinformation about how to properly use screened hive bottoms but we are working to correct this problem. A number of the beekeeping suppliers sell screen inserts rather than screened hive bottoms. Inserts increase the frequency of wax moth infestation and the at least some of the mites that fall below the screen insert onto the bottom board are able to find another host. The screened hive bottoms do not create an environment conducive for the reproduction of wax moth. Additionally, the mites drop out of the hive and cannot crawl back onto a bee.
Other less frequently used IPM tactics include removal or sealing off weak/dead colonies (0.5%), increasing the distance between colonies (0.5%), removal of most highly infested colonies from apiary (1%), selection of apiary location (5% of beekeepers), removal of sealed brood – either drone or worker (5%), resistant bee stock (20% in any one year), and splitting colony (25%). Based upon the responses we received from the surveys, workshops and apiary inspections, between 15% (855) and 25% (1400) of beekeepers have implemented two or more IPM varroa control tactics. We exceeded our second target.
While there seems to be an understanding among workshop participants of the efficacy of the removal of weak or dead colonies to prevent robbing (and the spread of mites), few beekeepers are implementing this tactic. Colony removal is implemented less frequently than sealing off a colony because removal is extremely time intensive and a major change in colony management. Either tactic requires a beekeeper to visit his/her apiary more frequently than is typical. We are continuing to work with beekeepers to improve the practicality of this tactic and will continue to emphasis this tactic in future workshops because this tactic not only would reduce the spread of mites through an apiary it also would reduce the spread of other diseases. If our estimate of the adoption rate of this tactic is correct, approximately 25 beekeepers are visiting their apiaries frequently enough to make the removal or the sealing off of a hive an efficacious method to reduce the spread of mites.
A few beekeepers have increased the distance between colonies to reduce the impact of drifting. When beekeepers learned that placing colonies in a long line would increase drift, they slowly altered the layout of their apiaries. Once research is completed this year (summer 2007) on the impact of spacing on bee drift, we expect to see beekeepers implement this tactic more frequently. Once 5% of more beekeepers implement this tactic we expect there will be a substantial jump in adoption rate because there are several advantages to the beekeeper of increasing spacing. The most obvious one is the ability of one colony to influence the behavior of another colony is reduced. Others include decreased robbing and more room to maneuver while working colonies. This tactic has several limitations including 1) larger operations will have greater difficulty increasing colony spacing; 2) additional apiaries may be needed to accommodate the colonies that had been in a single apiary; and 3) the cost of a bear fence may be higher if a larger area needs to be enclosed. Assuming our estimate of the adoption rate of this tactic is accurate, approximately 25 beekeepers are increasing the spacing between their colonies to reduce mite populations.
While a number of beekeepers have seen the impact that apiary location can have on mite population size this is a difficult tactic to implement. Many beekeepers in the MAAREC region have lost apiaries in recent years because some property owners are no longer willing to allow bees to be housed on their property. As the availability of apiary locations is reduced, even more ideal apiary locations are lost. Assuming our estimate of the adoption rate of this tactic is accurate, approximately 25 beekeepers in the MAAREC region are selecting apiary locations that reduce mite populations.
Sealed brood removal is considered to be too time intensive by most beekeepers. While this tactic is used extensively by European beekeepers with small operations, American beekeepers find this method to be contrary to most common colony management regimes. We have been working with a few beekeepers to reduce the work involved and to devise a routine for the insertion of drone comb (the most efficacious tactic) and subsequent removal, freezing and reinsertion. Even though this tactic is not looked upon favorable by many beekeepers, approximately 280 beekeepers in the MAAREC region are using this method. These beekeepers tend to be individuals who are the most reluctant to use miticides and tend to have between 1 and 25 colonies.
A number of purportedly resistant stocks are available for beekeeper purchase. Unfortunately there is tremendous variability in the efficacy of the stock with the same stock, e.g., Russian, being reported as effective in one year but not effective in another year. It is unclear how much this variability is due to the stock itself rather than differences between beekeeper operations. In any particular year there are approximately 1,110 beekeepers in the MAAREC region who will have purchased resistant queens. A beekeeper who purchased resistant stock but did not see an improvement in colony survivorship will not necessarily purchase resistant stock again even though the reason for the failure of colonies to over winter may be due to a variable other than the size of mite population.
Beekeepers commonly split strong colonies to increase the total number of colonies. Some beekeepers have found this to be an effective way to reduce mite populations. Beekeepers are reporting to each other that colonies split either at the end of their first year of existence or early in their second year are more likely to survive beyond the normal 2 year life expectancy of colony not treated with a miticides. Because “making splits” is a common management technique, this mite reduction tactic is becoming popular. If the estimated adoption rate of this tactic is accurate, approximately 1,400 beekeepers in the MAAREC region are selecting apiary locations that reduce mite populations.
Target Three: Three hundred of the approximately 5000 hobbyists and 700 sideliners in MAAREC were expected to participate in planning workshops and10 beekeepers will participate in the evaluation of IPM tactics plus mite monitoring.
We fell short of the project target of 300 beekeepers attending planning workshops. It was nearly impossible to get beekeepers to come to these meetings. Rather than forgo the participating of beekeepers in the planning of the kinds of IPM tactics that would be available or limit the recruitment of beekeepers to participate in the monitoring program, we attended every beekeeper meeting we could during the first year and a half of this project. At each meeting beekeepers were recruited to undertake a study of any IPM tactic they thought worthwhile and/or to participate in colony monitoring.
Target Four: Ten beekeepers were to be recruited each year to participate in the testing of IPM tactics. And, the ten beekeepers were to hold a workshop at his/her apiary to demonstrate IPM tactics and monitoring. Fifty beekeepers were expected attend each apiary workshops.
We met or exceeded our goal to recruit beekeepers to participating in the scientific testing of IPM tactics to control varroa. Each year between 10 and 20 beekeepers agreed to undertake studies. Each participating beekeeper indicated that they found the experience worthwhile, even if they stopped participating midway through the summer. The results of a one study were of sufficiently high quality that the data have been prepared for publication. The manuscript is written and is being reviewed by each of the participating beekeepers prior to submission.
We did not meet our goal of 50 beekeepers attending workshops at the apiaries of beekeepers who participating in the testing of IPM tactics. Scheduling these workshops with the beekeepers was extremely difficult, participating beekeepers lack interest in holding the workshops and attendance at the workshops was virtually non-existent. Instead of trying to force the workshop model on reluctant individuals, we, along with the participating beekeepers, presented results at many meetings. The presentations by the beekeepers were especially well received.
Target Five: “40-80 (workshop participants) are expected to implement multiple IPM tactics.”
We achieved this goal even though we were unable to hold workshops at beekeeper apiaries. See Target Two.
Target Six: “Approximately 200 beekeepers each year were expected to begin monitoring each year.”
We achieved this goal. Each year between 25 and 50 beekeepers volunteered to monitor for mites and send their data to Penn State for verification of threshold efficacy. Based upon survey results and other sources (See Target One) more than 200 beekeepers (4% of the hobbyist and sideline beekeepers in the MAAREC region) each year began monitoring for varroa mites.