Sustainable parasitic mite control for honeybees

2004 Annual Report for LNE03-188

Project Type: Research and Education
Funds awarded in 2003: $134,710.00
Projected End Date: 12/31/2006
Matching Non-Federal Funds: $75,882.00
Region: Northeast
State: Pennsylvania
Project Leader:
Dr. Nancy Ostiguy
Pennsylvania State University

Sustainable parasitic mite control for honeybees


The existence of honey bees is threatened by an obligate external parasite – the varroa mite. Feral bees have almost completely been eliminated from the environment while the maintenance of managed honey bees for pollination and honey and other hive products has been made extremely difficult. Beekeepers are dependent primarily on miticides for varroa control. The use of these chemicals is not sustainable because resistance development by the mite, hive wax contamination (the wax serves as a source of continuous low level exposure for bees during all life stages, especially egg, larva and pupa), and hive product contamination. This project is designed to help beekeepers reduce their use of miticides. The resulting residues in wax and bee products will be reduced along with production costs, through decreased colony mortality. The supply of healthy bees for honey production and field crop and wild plant pollination will increase

Two beekeeper behaviors are targeted for change. Monitoring of colonies for varroa mites, done by few beekeepers currently, will increase. This change will reduce pesticide use because miticides will not be applied to colonies that do not exceed the threshold or that have such high mite levels that treatment will not prevent colony death. The second change, adoption of at least two Integrated Pest Management (IPM) tactics to control varroa, will also reduce pesticide use by lowing mite levels in colonies. The first goal will be achieved by recruiting beekeepers to monitor varroa levels in their colonies. Beekeepers choose the monitoring method – either sticky boards or powdered sugar shake – and track the mite levels in their colonies throughout the spring, summer and fall. These data, along with overwintering success of monitored colonies are be submitted to Penn State for analysis. We have found during the first year that early spring monitoring may be a very important predictor of future mite levels and mite spread through the colonies. Thus we are beginning monitoring earlier in the season. An additional inducement for beekeeper participation in this effort is that these data will help to verify threshold levels and the relationship to overwintering success, which beekeepers are very interested in knowing. The second goal, adoption of IPM tactics to control varroa, is being achieved by recruiting innovative beekeepers to conduct research projects focused on varroa control. Workshops are being held this spring to demonstrate the practical aspects of how to implement IPM tactics. The experiments and workshops will continue to be initiated.

Objectives/Performance Targets

Two beekeeper behaviors are targeted for change: 1) monitoring: 500-1000 beekeepers will monitor varroa levels and 2) implementation of IPM tactics: 100 beekeepers will implement at least two IPM tactics. Approximately 200 beekeepers each year will be recruited to begin monitoring. Some will be successful at monitoring all season while others will not. We will encourage those who were successful to continue participating in subsequent years while those who stopped partway through the season will be asked to make another attempt to tract the mites in their colonies.

Of the approximately 5000 hobbyists and 700 sideliners in MAAREC, 300 beekeepers are expected to participate in planning workshops. Ten beekeepers from the 300 participants will evaluate IPM tactics. Workshops will be held at the beekeeper’s apiary to demonstrate IPM tactics and monitoring, with approximately 50 beekeepers attend each. During the second year 40-80 beekeepers will implement multiple IPM tactics.

Beekeepers are expected reduce their use of miticides in their honey bee colonies. The result will be lower residue levels, by at least 50%, reduced production cost of production due to decreases in the annual colony mortality from 40-60%, and increases in the supply healthy bees for honey production and pollinating field crops and wild plants.

Verification of reaching our targets will be obtained through annual beekeeper surveys. Additionally, we will obtain the annual statistics of the beekeeping industry from each MAAREC state to verify changes in management practices.


Two beekeeper behaviors have been targeted: 1) monitoring of colonies for varroa mites, done by few beekeepers currently, will increase and 2) adoption of at least two Integrated Pest Management (IPM) tactics to control varroa. Forty-eight beekeepers have been recruited to begin monitoring for varroa in June 2004. At this time we have approximately 100 beekeepers (last years recruits and those who have volunteered thus far this year) submitting data to be used in the evaluation the recommended threshold for varroa. Additional beekeepers (approximately 100) are monitoring their colonies but not submitting their data. We are continuing to recruit additional beekeepers. As we did last year, announcements for recruiting more beekeepers have been sent to state and local beekeeping associations for insertion into newsletters. A regional announcement is on the MAAREC web site. More beekeepers will be recruited during the next 4 months at various state and county beekeeper meetings, through newsletter announcements and direct contact by apiary inspectors and study personnel.

The target for the number of beekeepers participating in studies was exceeded last year. Over 15 beekeepers participated in varroa control studies in the MAAREC region.

The implementation IPM of tactics is likely to be beyond the target of 100 beekeepers implementing at least two tactics. All of the beekeepers submitting their mite monitoring data for the threshold evaluation have implemented at least one IPM tactic and most have implement two or more. The first workshops will be held in March and April 2005. The turn out is expected to be over 100 beekeepers.

Additional data on both monitoring and implementation of IPM tactics will be available after the survey data has been analyzed. State apiary inspection data is currently being collated by the various state agencies. We will begin to evaluate these data soon.

Impacts and Contributions/Outcomes

The evaluation of the distribution of mites within an apiary produced data we continue to test using other apiaries. We continue to see a spatial concentration of colonies with high levels of mites and are using apiary and colony level humidity, temperature, wind and other weather data to predict trends. A new observation resulting from early summer mite collections is leading us to reanalyze all mite data to determine if we can predict which colonies will exceed threshold later in the season. We also have observed a potential ‘seeding’ effect. Colonies with the highest mite levels in the early summer seem to be the source for mites to migrate to other colonies. We will be monitor mites in colonies in late spring as well as for the remainder of the season to further test these results. Additionally, beekeepers participating in the mite monitoring project will be asked to begin monitoring earlier in the season to help us determine the accuracy of our observation. If seeding is occurring, it may be possible apply a miticide in spring to these colonies only. This would reduce the risk of colony death from mites and viruses.

Last year a group of beekeepers (4) tested the survivorship of overwintered colonies using the fall mite thresholds. Instead of treating all the colonies with a miticide in September, colonies were treated or not depending upon the following criteria. Colonies with mite levels substantially below the threshold were not treated. Colonies with mite levels substantially above the threshold were treated. Colonies with mite levels between the two extremes were treated or not depending upon the beekeepers aversion to losing colonies. These criteria resulted in half the colonies not being treated with a miticide. Survivorship of all colonies was recorded. Two conclusions can be made from the data. The timing of the decision to treat or not treat is crucial. If one treats for varroa too late in the year, and viruses are present in the colony, the colony has a very high chance of dying even though mite levels are low after treatment. The survivorship of colonies that were treated, irrespective of mite level, was poor; approximately 50% of these colonies died. We are continuing to evaluate survivorship of colonies at different mite levels and we are also (in another project) evaluating the interaction between viruses and mites on colony survival.

Formic acid in a 1 or 2 day treatment was tested by three beekeepers. A significant loss of adult mites and mites still in capped brood was observed in treated colonies and, at the higher formic acid doses, queen loss was also seen. Normally queen loss would be a sufficient reason to stop testing this control tactic but a number of beekeepers, including two conducting this work, are interested in using formic acid to remove the queen when requeening is desired, while at the same time reduce mite levels. We are continuing to evaluate this tactic and plan to expand our tests to include oxalic acid and two formulations of essential oils. We will be comparing efficacies and the ambient conditions needed for optimal efficacy.

This project benefits sideline and hobbyist beekeepers and those who rely on honey bees for pollination and bee products. Beekeepers apply miticides to their colonies without knowing if the level of mites in the colony is sufficient to warrant a treatment. This unnecessary use of miticides results in adverse impacts on honey bees, increased costs from pesticide unnecessary use and potential contamination of hive products. This project is reducing the use of miticides in honey bee colonies through monitoring of varroa and implementation of IPM tactics. The beekeeper toolbox is being expanded by increasing beekeeper knowledge of how to effectively monitor for varroa and implement non-pesticide options for varroa control. The reduction in pesticide use results in the lowering production costs and pesticide residues in bee products and the rising of the supply healthy bees for honey production and pollinating field crops and wild plants.


Dewey Caron

[email protected]
University of Delaware
250 Townsend Hall
Newark, DE 19716
Office Phone: 3028318883