A Sustainable Approach to Controlling Varroa Mites of Honey Bees

Final Report for LNC99-152.1

Project Type: Research and Education
Funds awarded in 1999: $86,286.00
Projected End Date: 12/31/2001
Matching Non-Federal Funds: $25,000.00
Region: North Central
State: Minnesota
Project Coordinator:
Marla Spivak
University of Minnesota
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Project Information

Summary:

Honey bees bred for hygienic behavior demonstrate good resistance to diseases and partial resistance to the parasitic mite, Varroa destructor. Bees bred for “Suppression of Mite Reproduction” (SMR) demonstrate better mite resistance than hygienic bees or bees imported from Russia by the USDA. We began testing reciprocal crosses between hygienic and SMR traits to increase mite resistance while retaining disease resistance, high honey production and brood viability. Our outreach program has been successful in transferring the resistant queens and breeding technology to beekeepers with the goal of reducing the use of pesticides and antibiotics within honey bee colonies.

Introduction:

Honey bees, Apis mellifera, are the primary pollinating insect in North America. With the introduction of the parasitic mite, Varroa destructor, into the U.S. in 1987, the number of feral and managed honey bee colonies has decreased significantly. These mite pests have had a devastating effect on honey bee colonies and beekeeping businesses. To control V. destructor, beekeepers have resorted to the in-hive use of pesticides. For almost ten years, these mites were controlled successfully with the synthetic pyrethroid fluvalinate (Apistan“), applied as plastic impregnated strips within the hive. However, in recent years, the mites developed resistance to this compound. Most states now have Section 18 approval to use coumaphos, an organophosphate, as an alternative to fluvalinate, but this summer (2001) mite resistance to coumaphos was demonstrated in Florida (P. Elzen, pers. comm.).

Another recent development since this proposal was funded is the spread of a devastating disease of honey bee colonies, American foulbrood (AFB), caused by the bacterium Paenibacillus larvae larvae. Most colonies infected with AFB eventually die and the spores left in the wax comb remain highly infectious for over 50 years. Until two years ago, this disease was controlled successfully with the antibiotic, oxytetracycline (Terramycin“). However, the incidence of AFB resistant to oxytetracycline has spread dramatically (Miyagi et al. 2000). New antibiotics are being tested for control of this disease, but they are not available to date.

The goal of our research has been to breed for mite resistant honey bee stock and transfer the breeding technology to queen producers in the U.S. so they can breed for resistance to V. destructor from among their own lines of honey bees and limit the use of pesticides within their colonies. Since 1994, we have been breeding bees for hygienic behavior. Hygienic behavior is one of several mechanisms of honey bee defense against the Varroa sp., both in the original host of the mite, Apis cerana in Asia, and in its new host, A. mellifera (Boecking and Spivak, 1999). Varroa sp. mites spend a portion of their life cycle feeding on adult bees, and the other portion reproducing and feeding on the hemolymph (blood) of worker and drone pupae within wax covered cells. Bees that display hygienic behavior are able to detect a portion of the mite-infested brood, uncap the cell and remove the infested pupae (Spivak 1996). The mother (foundress) mite may escape during the removal process, but her offspring in the cell are destroyed by the bees. Thus, hygienic behavior reduces the reproductive potential of the mite.

In addition to mite resistance, it has long been known that bees that express hygienic behavior have the ability to detect, uncap, and remove diseased brood from the nest. In so doing, they remove the innoculum before the causative organism reaches the infectious (spore) stage (Woodrow and Holst, 1942). In early research, hygienic behavior was found to be the primary mechanism of resistance American foulbrood (Rothenbuhler, 1964), and also to another disease, chalkbrood, caused by the fungus, Ascosphaera apis (Gilliam et al., 1983). In research not directly funded by SARE, but related to this proposal, we tested whether our hygienic line, which is derived from different bees than the early studies, was resistant to AFB. We challenged hygienic colonies with spores of P. larvae larvae that were resistant to Terramycin, and found that 11% of the hygienic colonies had clinical symptoms of AFB by the end of the experiment vs 89% of the non-hygienic colonies (Spivak and Reuter, 2001). In addition, the hygienic colonies had significantly less incidence of naturally occurring chalkbrood disease. Thus, our hygienic line demonstrates a high level of resistance to both diseases.

The focus of my research funded by SARE since 1997 was to determine if bees bred specifically for hygienic behavior would have sufficient resistance to the mite to reduce the frequency of pesticide applications in commercial beekeeping operations, and thus save beekeepers money. In collaboration with beekeepers, we tested the hygienic bees in commercial apiaries over two large-scale field studies. Our results indicated that colonies headed by naturally mated hygienic queens from the breeding program had significantly fewer V. destructor, less disease, and produced more honey than unselected, commercial colonies for up to one year without treatment (Spivak and Reuter, 1998; 2001). However, when mite infestation pressure was high (e.g., in migratory beekeeping operations when hundreds of colonies are moved together on trucks to a new location), the rate of removal of infested brood by hygienic bees could not outpace the rapid mite population increase, and the hygienic colonies required more frequent treatment to prevent collapse.

To resist V. destructor, bees must have heritable mechanisms of reducing the survivorship and/or reproductive success of the mites. Although hygienic behavior is one heritable mechanism of resistance, other research suggests that the suppression of mite reproduction on worker brood may be a more important mechanism of resistance (Camazine,1986; Harbo and Hoopingarner, 1997, Harbo and Harris, 1998). The reduced fertility has been attributed to a genetic characteristic of the bee, but the mechanism is still unclear. With this round of SARE funding, we initiated studies in which bees bred specifically for Suppression of Mite Reproduction (SMR) were crossed with bees bred for hygienic behavior with the goal of increasing mite resistance while maintaining disease resistance and high honey production.

Selection for resistant bee stocks has obvious importance for the health and survival of honey bee colonies, but until we began our research and extension efforts to promote the use of resistant (hygienic) stock, beekeepers were not interested in bees bred for resistance because it was simply easier to apply antibiotics and pesticides than to maintain selected lines of bees. The combination of the development of resistance to the treatments and our persistent research, extension and education efforts are finally motivating beekeepers to maintain and use resistant lines of bees rather than relying solely on pesticides and antibiotics.

Original Objectives
1. Continue the breeding program for honey bees that display hygienic behavior, one mechanism of resistance to the mites
2. Screen hygienic line of bees for other mechanisms of resistance to V. destructor
3. Test strategy of combining mite resistant bees with alternative treatment to limit use of conventional pesticides
4. Conduct survey on performance of hygienic colonies in commercial apiaries

Project Objectives:

1. Continue the breeding program for honey bees that display hygienic behavior, one mechanism of resistance to the mites
2. Screen hygienic line of bees for other mechanisms of resistance to V. destructor
3. Test strategy of combining mite resistant bees with alternative treatment to limit use of conventional pesticides
4. Conduct survey on performance of hygienic colonies in commercial apiaries

Cooperators

Click linked name(s) to expand
  • Gary Reuter
  • Duane Swenson

Research

Materials and methods:

Objective 1. Continue the breeding program for honey bees that display hygienic behavior, one mechanism of resistance to the mites

Methods: The degree of hygienic behavior of selected colonies is determined using a freeze-killed brood assay in which the amount of time is recorded for bees to detect, uncap and remove a comb section containing freeze-killed pupae (Spivak & Reuter, 1998) Colonies that remove freeze-killed brood within 48 hours consistently over two trials are considered hygienic, whereas, colonies that take longer than one week to remove the dead brood are considered non-hygienic (Spivak and Downey, 1998). To establish hygienic lines, queen bees are raised from the most hygienic colonies. Each daughter queen is instrumentally inseminated with mixed semen from drones (males) of different hygienic colonies. A similar procedure is used to develop non-hygienic (control) lines. Insemination is necessary to control the genetics of the trait because honey bee queens naturally mate on the wing with multiple males from many colonies in the area who may not carry the hygienic trait. Inseminating queens ensures that the trait will be fixed in their progeny. A similar procedure is used to develop non-hygienic (control) lines. The progeny of inseminated queens is again assayed before subsequent experiments are conducted. Since the beginning of the breeding program (1994), new colonies have been screened for hygienic behavior using the freeze-killed brood assay to increase the number of sublines (queen lines) in the breeding program.

Objective 2. Screen hygienic line of bees for other mechanisms of resistance to V. destructor

We screened the hygienic line for the SMR trait by inspecting infested brood to determine the rate of unsuccessful mite reproduction. We did not find sufficient number of colonies in which the mites were not reproducing successfully on worker brood to begin further selection. Reviewer 1 of our proposal thought it would be a more fruitful line of research to incorporate (combine) a line of bees bred for suppression of mite reproduction with the hygienic line to increase the degree of mite resistance. After reviewing the results of our data from Objective 3 which indicated that the SMR line performed well in a commercial beekeeping operation, we decided to follow the reviewers suggestion.

Accordingly, we obtained two SMR breeder queens from Dr. John Harbo at the USDA Bee Research Lab in Baton Rouge, LA. We began testing the reciprocal crosses between the hygienic and SMR lines this summer, 2001 at the University of Minnesota. In mid-June, we established 10 colonies of the HYG x SMR cross, 10 SMR x HYG, and 6 each of SMR x SMR and HYG x HYG as controls. The colonies were initiated with an equal number of bees and mites using the methods of J. Harbo. In brief, in mid-June we shook 96 pounds of bees (approximately 336,000 bees) from various mite-infested colonies into a giant screened box. Samples were taken from the box to determine the average number of mites on the bees. From the giant box, we scooped 3 pounds of bees into each of 32 smaller boxes (commercial beekeeping" packages") and introduced a caged, inseminated queen into each package. After 3 days, we shook the bees in each package into standard beekeeping equipment with wax combs and released the queens so they could begin laying eggs in the combs. In this way, all colonies began with equal numbers of bees and mites. We let the colonies establish themselves for two months until all the bees became progeny of the inseminated queens. In August, we measured brood viability, assayed each colony for hygienic behavior, and counted the number of mites infested adult bees and worker brood (See Results).

Objective 3. Test strategy of combining mite resistant bees with alternative treatment to limit use of conventional pesticides

In collaboration with commercial beekeepers, our goal was to test the integrated, strategy of treating four bee lines that demonstrate mite resistance with formic acid, a naturally occurring organic acid. The four lines were the hygienic line, the "SMR" line, a line of bees imported from Russian by the USDA (Rinderer et al. 1999), and the "commercial Italian" line bred by beekeepers. We conducted a large-scale field test to compare the mite loads and honey production between the lines and their survivorship after treatment with formic acid. Although the efficacy of formic acid ranges from 60-80%, we thought it might provide sufficient control so that partially resistant colonies could survive without conventional pesticides. However, we had to modify our experimental design for this objective in one way. We planned to test whether an annual treatment of formic acid would provide sufficient control for the continued survival of hygienic colonies in both a migratory and non-migratory beekeeper’s apiaries. The migratory beekeeper decided not to transport his colonies from MN to MS for economic reasons, so we only tested in non-migratory situations.

Part 1: In collaboration with Mr. Duane Swensen, we raised daughter queens from hygienic, SMR, Russian and commercial Italian lines. All queens were reared in March in either Baton Rouge, LA (SMR and Russian queens) or in Mississippi (hygienic and Italian queens), and were allowed to mate naturally in Mississippi with drones from D. Swensen’s apiaries. Thus, all queens mated with the same pool of drones, so any differences in mite resistance or other characteristics would be due to the genetic effect of the queens. All queens were marked on the thorax with paint to denote their line of origin and were transported to Minnesota in May. The colonies were placed randomly in 3 apiaries near Belle Plaine, MN, each containing approximately 32 colonies. The bees had been treated with coumaphos in fall of 1999 in Mississippi, but were not given additional treatments until the fall of 2000, when formic acid was applied (see below).

In May, 2000 we evaluated the colony strength (frames of bees and brood) of all colonies, the presence of disease, and the number of mites on adult bees and within worker brood. In late August, we recorded the amount of honey harvested from the colonies, and in late September, before formic acid treatment, we again evaluated the number of mites on adult bees and within worker brood.

In early October, our commercial beekeeper collaborator randomly chose 10 colonies of each type to keep over the winter months. We treated the colonies with formic acid using the methods developed by Dr. Medhat Nasr of the Ontario Beekeeping Association in Canada (Calderone and Nasr, 1999). Fiber boards (Homosote, made of pressed newspaper) and enclosed in Ziploc Vegetable plastic bags containing 1/4" holes were soaked in 65% formic acid for 3 days (250m./pad). The pads were placed on 1/2" slats placed over the frames on top of the colony (to ensure aeration and evaporation). A 3" rim was placed on top of the colony, under the outer cover, to accommodate the acid pad. The pad was left in the bag for 10 days, then was removed from the bag and left another 10 days. The efficacy of formic acid depends on the temperature and thus evaporation rates. Because temperatures in MN were relatively cool in late October, we removed the pads from the bags to facilitate full evaporation of the acid.

In May, 2001 we evaluated the survivorship of the wintered colonies and assessed their mite loads. At that point we terminated this portion of the experiment.

Part 2: In this part of Objective 3, we raised daughter queens from the hygienic line and from the SMR line at the University of Minnesota Agriculture Experiment Station in Rosemount in June, 2000. All queens were allowed to mate naturally with drones in the surrounding area, and were painted on the thorax to denote their line of origin. The queens were maintained in colonies established from divides (wintered colonies that were divided into two separate colonies). The experimental colonies were maintained in two apiaries, located approximately 2.5 miles from each other. The wintered colonies from which the experimental colonies were established were treated with coumaphos in Fall, 1999, and at the time the divides were made, mite samples from adults indicated that the colonies had no detectable mites.

In September, when all the bees in the colony were progeny of the new queens, we sampled the colonies for mites on adults and mites on worker brood in both apiaries. Since all colonies had very low mite levels, we did not treat them before winter. All colonies were wintered in the same locations, and continued measurements of survivorship and mite levels were made in May 2001.

Objective 4. Conduct survey on performance of hygienic colonies in commercial apiaries. To obtain feedback from beekeepers on the hygienic line of bees, we distributed over 100 one-page surveys to beekeepers in attendance at the state beekeeping association meetings in MN, ND, WI, SD. Unfortunately only 10 people responded. However, we have received much positive feedback from beekeepers from other sources, which is included below (Results and Attachments).

Research results and discussion:

Objective 1. Continue the breeding program for honey bees that display hygienic behavior, one mechanism of resistance to the mites

To date, we have 12 sublines within the hygienic line, which is sufficient to maintain sufficient genetic diversity within the breeding stock and to avoid inbreeding. Over the last three years, we have distributed hygienic breeder queens to beekeepers within the states that have contributed matching funds toward this research project: Minnesota, North Dakota, South Dakota, Wisconsin, and Iowa. In particular, we have an agreement with the MN Honey Producers Association to donate 12 Hygienic breeder queens (inseminated, tested queens) to the association every year. The association auctions the queens to beekeepers to raise money which they can then donate toward further research. The beekeepers raise daughter queens from the breeders for their own colonies, and then give a certain number to a regional beekeeping supplier (B&B Honey Farm, Houston, MN), who then sells the hygienic stock to beekeepers in the region. B&B Honey Farm has sold over 10,000 queens to beekeepers in the last two years. This is a substantial number, which indicates the interest in the stock by beekeepers.

In addition, M. Spivak donates breeder hygienic queens to a commercial queen producer in CA (Tom Glenn of Glenn Apiaries) who propagates the stock and sells it to beekeepers throughout the US (http://member.aol.com/queenb95/web/home.html) In response to his increasing sales, other commercial bee breeders in the US are beginning to select for and sell hygienic stock. Our ultimate goal has been to encourage beekeepers to breed for resistant lines of bees from within their own bee stocks. To this end, we have been successful (see Farmer Adoption).

Objective 2. Screen hygienic line of bees for other mechanisms of resistance to V. destructor

On 24 August, we measured the amount of brood (larvae and pupae) in the reciprocal crosses (HYG x SMR; SMR x HYG) and the original lines using wire grids to determine brood viability. A number of the original queens in the colonies had died or been superseded by this time, particularly the SMR queens. Also, it became apparent that there was a problem with brood viability in the SMR x SMR colonies (see Table 1). The SMR x HYG colonies retained good brood viability. Dr. John Harbo, the researcher who bred the SMR line, also found the same problem this summer in his colonies in Louisiana. (NOTE: We have not yet run statistical analyses of the data in tables that follow.)

At his point, it is unclear whether the SMR trait is deleterious to both mites and bees, or whether the line of bees Dr. Harbo bred the trait into has deleterious alleles. Most likely the problem with the SMR line is due to severe inbreeding because the majority of outcrossed SMR colonies (e.g., SMR queens mated to HYG drones) still retain good brood viability, and good mite resistance (see below).

On 23 August, we tested the colonies that had sufficient brood for hygienic behavior by freezing a section of the sealed brood in the comb using liquid nitrogen. After 24 hours, we recorded the percentage of freeze-killed brood that the bees uncapped and removed. Colonies that removed >95% of the dead brood within this time are considered "hygienic" and tend to have good resistance to brood diseases because they will also uncap and remove diseased brood from the nest before the disease becomes infectious. Our results indicated that all colonies removed >95% of the freeze-killed brood within 24 hours except for one colony in each cross. This result was very surprising; hygienic behavior is a recessive trait which means the colony will not express it unless both the queen and the drones she is mated with carry the alleles. We know that Dr. Harbo only selected for colonies that had low mite reproduction and low mite loads. Because the SMR x HYG and the SMR x SMR colonies (with enough brood to test) demonstrated hygienic behavior, it is reasonable to assume that hygienic trait is one of a suite of characters involved in total mite resistance and was inadvertently selected for in Dr. Harbo's breeding program.

On 27 August, we collected samples of adult bees in alcohol and calculated the number of mites per 100 bees. We also took combs containing live pupae back to the lab to determine mite loads. We opened 200 cells containing pupae approximately 3 days from emergence and calculated the number of mites per 100 brood cells. Table 2 shows that the colonies headed by SMR queens had the fewest mites on adults. However, the number of mites in brood cells was lowest in the SMR x SMR and the HYG x HYG colonies. There was no difference in the number of mites that did not reproduce among the crosses (data not shown) probably because so few mites were found in the brood overall.

On 10 October, there was no brood left in the colonies because the queens stopped laying eggs for the winter so we took another sample of adult bees to measure mite loads, and weighed the bees to determine the number of bees in the colony. From these measurements, we determined whether the mite loads (and bee populations) increased or decreased over the summer (Table 3). By this time, all the SMR x SMR colonies had died. The colonies were initiated in June with 1.7 mites per 100 bees. The number of mites in the HYG x SMR stayed constant, while it increased in the HYG x HYG colonies, and decreased in the SMR x HYG colonies.

From the remaining colonies, we chose 3 HYG x SMR and 3 SMR x HYG that had the highest mite loads, the most rapid removal behavior and the lowest mite counts (Table 4).

Discussion, Objective 2: We have sent the queens from Table 4 to our collaborator, Tom Glenn of Glenn Apiaries, California. He will raise daughter queens from these colonies in February and March (at a time when it is not possible to raise queens in Minnesota), and will artificially inseminate them with semen from males from both hygienic and SMR colonies. He will send 40 inseminated queens to us in April 2002. These queens will produce hybrid worker bee progeny, and the 40 colonies will be tested for disease resistance by inoculating the larvae with spores of chalkbrood and American foulbrood. In addition, we will test for honey production and will record other information important to beekeepers: temperament of the colonies (whether they sting excessively); colony strength (worker and brood populations) and brood viability. We will be submitting a proposal for another round of funding from SARE to continue with this line of research.

Objective 3: Test strategy of combining mite resistant bees with alternative treatment to limit use of conventional pesticides

Part 1. There were no significant differences among the 4 bee types (Italian, Hygienic, Russian and SMR) in the frames of bees and brood after the colonies were transported to Minnesota from Mississippi (Figure 1). This indicates the colonies were of equal strength when the experiment began.

Measures of honey production at the end of the summer (September 2000) indicated that the Russian colonies produced significantly less honey than the other bee types (Figure 2).
We sampled mite loads both on adult bees and in worker brood twice during the summer of 2000; at beginning of the experiment in June 2000, at the end of the summer in September 2000. It is important to note the y-axes in the following graphs; the mite levels in May 2000 were all under 0.5%, the levels in September rose to 10% on adult bees and 30% in the brood (Figures 3 and 4).

Ten colonies of each type were treated to control Varroa using formic acid as described in the Methods (the remaining colonies were moved to a different apiary and treated by the commercial beekeeper). Unfortunately, we were not able to obtain information on the survivorship of the colonies the next spring because the majority of the colonies died over the winter. The extreme mortality was due in part to the severity of the winter, and in part to the inexperience of the beekeeper in preparing colonies for the winter months in northern climates (he is a migratory beekeeper who always transported his colonies to Mississippi for the winter). In May, of the 10 colonies of each type, there were 2 Italian, 3 Hygienic, 6 SMR, and 3 Russian colonies remaining (Figure 5).

This experiment was terminated at this time. It was apparent to us that the SMR line had the highest degree of mite resistance, survived relatively well over the winter, and produced as much honey as the hygienic and Italian lines. Thus, we decided it would be the best strategy to combine the disease resistance of the hygienic line with the mite resistance of the SMR line, as described in Objective 2.

Part 2. Overall, 62% of the Hygienic and SMR colonies that we wintered at the University apiaries survived the winter. Although the colonies in this part of the study had adequate honey stores to last the winter, the severity of the winter was mostly likely responsible for the relatively high mortality of colonies. The mite levels on adult bees in Apiary 1 remained very low after 2 years of not being treated. The mite levels in Apiary 2, however, increased in May. The Hygienic colonies had significantly more mites than the SMR colonies in that apiary (Figure 6). To obtain sufficient bees and mites for our experiment in Objective 2, we decided to terminate the experiment in Apiary 2 so we could shake out the bees and their mites into the giant box.

Objective 4. Conduct survey on performance of hygienic colonies in commercial apiaries. Copies of the completed survey responses are included in the Appendix. Overall, the responses indicated that the beekeepers were satisfied with the hygienic stock (10 of 10 respondents responded affirmatively). They saw little to no chalkbrood (7 of 10) or AFB (10 of 10). Those that compared the hygienic colonies with another line of bees (7 respondents) said the hygienic colonies produced as much honey as the other line (5 of 7), the hygienic colonies had better brood patterns (4 of 7); less chalkbrood (4 of 7); and less AFB (3 of 5; two "didn't know"). Some respondents gave informative written comments at the bottom of the form.

In addition to this feedback, we have attached other letters and articles from beekeepers which talk about their positive experiences with hygienic colonies (see Appendices).

Research conclusions:

With the introduction of the destructive parasitic mite, Varroa destructor, into the U.S., beekeepers have had to resort to using pesticides within their beehives to prevent devastating and expensive colony losses. Colony losses have more than doubled in many cases even with the use of the pesticides due to reinfestation and increase in the overall stress imposed on the colonies by the mites. Operating costs have increased dramatically because the pesticides are expensive and more labor is required to apply them. The most sustainable solution is to reduce the dependency on pesticides by breeding bees that can defend themselves against the mites and diseases. These bees would be healthier and more able to withstand the stress of continued mite infestation and disease exposure.

Our research demonstrates that colonies bred for hygienic behavior have good resistance to chalkbrood and American foulbrood diseases, and partial resistance to Varroa mites, particularly under low mite infestation pressure. Our current efforts to blend the hygienic trait with the SMR trait will increase the mite and disease resistance by increasing the bees' ability to suppress mite reproduction and remove infested brood. Our goal is to eliminate the use of pyrethroids and organophosphates entirely in beehives by using resistant stock, or minimally to reduce the number of treatments required. Most beekeepers treat their colonies twice annually with the synthetic pyrethroid, fluvalinate, or more recently with the organophosphate, coumaphos. In the last two years, the mites have developed resistance to fluvalinate and in 2001, mites were found in Florida that were resistant to coumaphos. Coumaphos has temporary registration (Section 18 status), but it is unlikely the EPA will register this compound for long-term use. If beekeepers could half the number of treatments they apply, this small reduction in pesticide use would reduce the added operating cost in half.

A reduction in pesticide use by beekeepers will enhance environmental quality and economic viability of individual beekeeping operations, strengthen an agricultural system (beekeeping) which is based on small and moderate-scale owner-operated farms; protect human health and safety by preventing the risk of contaminating honey and hive products ; and promote the well-being of honey bees -- the world’s vital pollinators of crops, gardens, and wildflowers.

Economic Analysis

The number of beekeepers in the North Central States (and the U.S.) is small relative to the number of corn and soybean farmers; beekeeping is a specialized art and life-style that is not attractive to everyone. However, beekeepers play an extremely important role in the ecosystem because bees are such important pollinators of many commercial vegetable and seed crops (e.g., alfalfa, sunflowers, vine crops), commercial fruits (e.g., apples, cranberries, blueberries, strawberries), and home fruit and vegetable gardens. In addition, bees produce honey - a product well respected for being wholesome and pure. Control measures for diseases and mites have increased operating costs for beekeepers, and in recent years, many commercial beekeepers have gone out of business. Although other commercial and hobbyist beekeepers continue to operate, the combined effects of increased costs of controlling pests and diseases, the depressed honey market, and reduced colony survivorship due to habitat destruction and increased pesticide use on crops, have resulted in a drastic decline in national honey bee colony counts.

A commercial beekeeper with 2500 colonies currently spends $16,500 yearly to treat his/her colonies with fluvalinate(Apistan®), or coumaphos (CheckMite®) to control Varroa mites (2 applications/year; $1.65/strip, 4 strips/yr.). 2500 colonies is an average number of colonies necessary to sustain a livelihood. On an aggregate basis, Minnesota beekeepers spend approximately $990,000 each year on these pesticides alone. When antibiotics are added in to prevent the spread of bee diseases (Terramycin costs: $268/2500 colonies, or $16,080/150,000 colonies; the total expense per year exceed 1 million. Clearly, the costs of pesticides and antibiotics are prohibitive for an already challenged group of farmers.

One of the most cost-effective ongoing operating expenses that beekeepers have is the price of introducing new, young queens into their colonies. Many large commercial operators raise their own queens. Others purchase new queens for $8.00-12.00 each. New queens are introduced into at least half of the colonies in Minnesota annually. With access to queens from stocks that are mite-resistant and productive, beekeepers could reduce the amount spent on pesticides by one-half, reducing treatments to once a year, without any additional operating costs. Any reduction in pesticide use means increased profit for the beekeeper.

Farmer Adoption

There are approximately 4000 beekeepers in Minnesota, North Dakota, South Dakota, Wisconsin and Iowa, the states within the North Central Region that provide consistent financial support to the Apicultural Research program at the University of Minnesota. There are 550 registered beekeepers who manage approximately 150,000 honey bee colonies in Minnesota (the number of colonies is down 25% from 1998). There are 412 registered hobby beekeepers (those who manage 1-50 colonies), 68 registered sideline beekeepers (51-500 colonies), and 70 commercial beekeepers (more than 500 colonies). The commercial beekeepers own more than half of the total number of colonies in the state. Most commercial operators own 1,000- 3,000 colonies, and some have 4,000-6,000 colonies. There are approximately 260,000 honey bee colonies in North Dakota, 270,000 in South Dakota, 100,000 in Wisconsin, and 55,000 in Iowa.

Most commercial beekeepers raise their own queens, so the majority of queen sales are to hobby and side-line beekeepers. We have an agreement with the MN Honey Producers Association to donate 12 Hygienic breeder queens (inseminated, tested queens) to the association every year. The association auctions the queens to beekeepers to raise money which they can then donate toward further research. The beekeepers raise daughter queens from the breeders for their own colonies, and then give a certain number to a regional beekeeping supplier (B&B Honey Farm, Houston, MN), who then sells the hygienic stock to beekeepers in the region. B&B Honey Farm has sold over 10,000 queens to beekeepers in the last two years (letter attached). This is a substantial number, which indicates the interest in the stock by beekeepers. In addition, M. Spivak donates breeder hygienic queens to a commercial queen producer in CA (Tom Glenn of Glenn Apiaries) who propagates the stock and sells it to beekeepers throughout the US (http://member.aol.com/queenb95/web/home.html)

Thus, we have established a system to ensure that beekeepers in the North Central Region, as well as throughout the US, have a way to obtain the queens bred for both SMR and hygienic behavior. Principles of supply and demand operate here: if beekeepers demand resistant stock, bee breeders will be compelled to supply it. By distributing a limited number of resistant queens to beekeepers in the upper Midwest, beekeepers have tried the stock in their own apiaries. They have been pleased with the performance of the stock, and so are not putting pressure on the other queen breeders to select for the resistance also (see Appendices)

Participation Summary

Educational & Outreach Activities

Participation Summary:

Education/outreach description:

Dr. Spivak and Mr. Reuter offer an annual 3 day short course on "Beekeeping in Northern Climates" for the general public at the University of Minnesota. This course targets people that have never kept bees, but that have an interest in learning more about their biology and how to become a beekeeper. The course is based on sustainable practices, and includes discussion of responsible pesticide use and alternatives to chemical treatments. The average enrollment over the last 3 years has been 115 students. Most attendees were from Minnesota; however, others came from Wisconsin, Iowa, South Dakota, Missouri, and Nebraska. We also offer a course yearly in "Successful Queen Rearing" in which we teach experienced beekeepers how to breed and rear queens. In this course, we stress breeding queens for disease and mite resistance, and demonstrate techniques how this is done. The enrollment for this course is limited to 20 people due to the hands-on nature of the course content.

Dr. Spivak is regularly invited to speak at Beekeepers meetings throughout the North Central Region, as well as the US. In the last couple years, I have been invited to England, France, Italy, and the Czech Republic to speak to beekeepers about breeding for hygienic stock and disease and mite resistance. The desire for this knowledge is increasing worldwide.

In addition, I speak at Minnesota and Wisconsin fruit and vegetable growers meetings, and Wisconsin Cranberry Growers meeting, where I emphasize the value of honey bees in vegetable and fruit production, and of the importance of maintaining healthy honey bee colonies for this purpose. Mr. Reuter speaks to over 30 public schools and nature centers annually in the Twin Cities area of Minnesota. In these presentations, he stresses the importance of honey bees to our ecosystem.

To disseminate the findings of our work, M. Spivak has given 33 invited presentations at beekeeping meetings and scientific conferences (from Sept 1999- Nov 2001). In addition, Gary Reuter has given over 25 presentations at beekeeping meeting throughout the North Central Region and also over the US. He also has given over 30 presentations to public schools and nature centers on bees and beekeeping. We have published (or have in press) 12 refereed scientific articles and 8 abstracts/proceedings in the last two years. We gave two short courses each year to beekeepers and answered innumerable phone calls from beekeepers from all over the US. The majority of this information dissemination concerns hygienic behavior of honey bees and its utility in bee breeding. A full list of talks and publications is given below, and several are elaborated further in the Product Forms.

List of scientific and extension articles:

Haarmann, T., Spivak, M., Weaver, D., Weaver, B., Glenn, T. The effects of fluvalinate and coumaphos on queen honey bees (Apis mellifera L). in two commercial queen rearing operations. J. Econ. Ent. In press.

Spivak, M., Reuter, G.S. 2001 Resistance to American foulbrood disease by honey bee colonies, Apis mellifera, bred for hygienic behavior. Apidologie 32: 555-565.

Masterman, R. Ross, R., Mesce, K., Spivak, M. 2001. Olfactory and behavioral response thresholds to odors of diseased brood differ between hygienic and non-hygienic honey bees (Apis mellifera L.) J. Comp Physiol. A 187: 441-452.

Arathi, H.S., Spivak, M. 2001 Influence of colony genotypic composition on the performance of hygienic behavior in the honey bee (Apis mellifera L). Animal Behavior 62: 57-66.

Spivak, M., Reuter, G. S. 2001. Varroa jacobsoni infestation in untreated honey bee (Hymenoptera: Apidae) colonies selected for hygienic behavior. J. Econ. Entomol 94(1): 326-331.

Spivak, M., Boecking, O. 2001. Honey bee resistance to Varroa jacobsoni mites. In: Mites of the Honey Bee ( T. Webster & K. Delaplane, eds). pp. 205-227. Dadant & Sons, Hamilton, IL

Arathi, H.S., Burns, I., Spivak, M. 2000. Ethology of hygienic behaviour in the honey bee, Apis mellifera (Hymenoptera: Apidae): Behavioural repertoire of hygienic bees. Ethology 106: 1-15.

Masterman, R., Smith, B. Spivak, M. 2000. M. Evaluation of brood odor discrimination abilities in honey bees (Apis mellifera L.) using proboscis extension reflex conditioning. J. Insect Behav. 13(1): 87-101.

Elzen, P.J., Baxter, J.R., Spivak, M., Wilson, W.T. 2000.Control of Varroa jacobsoni Oud. Resistant to fluvalinate and amitraz using coumaphos. Apidologie 31: 437-441.

Miyagi, T., Peng, C.Y.S., Chuang, R.Y., Mussen, E.C., Spivak, M., Doi, R.H. 2000. Verification of oxytetracycline-resistant American foulbrood pathogen Paenibacillus larvae in the United States. J. Invertebr. Pathol. 75(1) 95-96.

Boecking, O., Spivak, M. 1999. Behavioral defenses of honey bees against Varroa jacobsoni Oud. Apidologie 30: 141-158.

Abstracts and Proceedings

Spivak, M. 2001. Mechanisms of American foulbrood resistance. EuroConference on Molecular Mechanisms of Disease Tolerance in Honeybees. Kraulpy near Prague, Czech Republic. pp 155-174.

Spivak, M., Reuter, G. 2001. Comparison of Hygienic, SMR, Russian an d Italian honey bees in a commercial apiary. Proc. Amer. Bee Res. Conf. Am. Bee J. 141: 894.

Spivak, M., Ross, R., Gramacho, K. 2001. Olfactory sensitivity of hygienic honey bees performing uncapping and removal behaviors. Proc. Amer. Bee Res. Conf. Am. Bee J. 141: 894.

Arachavaleta-Velasco, M.E., Hunt, G.J., Glenn, T., Spivak, M. 2001. Genetic analysis of the hygienic behavior of backcross honey bee colonies. Proc. Amer. Bee Res. Conf. Am. Bee J. 141: 885.

Haarmann, T.K., Spivak, M. 2000. The effects of fluvalinate and coumaphos on queen honey bees in commercial queen rearing operations. Proc. Amer. Bee Res. Conf. Am. Bee J. 141: 889.

Spivak, M. 2000. Non-reproduction in Varroa jacobsoni. 2nd Int. Conf. Africanized Honey Bees and Bee Mites, Tucson, AZ. April 10-12, 2000.

Peng, C.Y.S., Miyagi, T., Chuang, R.Y., Doi, R.Y., Spivak, M., Mussen, E.C. 2000. Finding antibiotic-resistant American foulbrood pathogen in US and its implication on beekeeping. 2nd Int. Conf. Africanized Honey Bees and Bee Mites, Tucson, AZ,.

Spivak, M. 1999. The potential for breeding Varroa-resistant honey bees. Proc. Apimondia ’99 Congress XXXVI , Vancouver, Canada 12-17 Sept. 1999, p. 59.

Haarmann, T.K, Spivak, M. 1999. The effect of fluvalinate residue accumulation on queen health and performance. Proc. Apimondia ’99 Congress XXXVI , Vancouver, Canada 12-17 Sept. 1999, p. 104.

Spivak, M., Boecking, O. 1999. Resistance to Varroa jacobsoni by Apis mellifera: a perspective for the beekeeping industry. Apiculture for the 21st Century. R. Hoopingarner & L. Conner (eds.) Wicwas Press, Connecticut. pp. 109-118.

List of Invited Presentations given by M. Spivak to beekeeping associations and scientific conferences (September 1999 - November 2001).

Colorado Beekeepers Assoc. "Pesticides in Bee Colonies" Colo Springs, CO Dec 6. 2001

MN Honey Producers Assoc. "Research Update" Alexandria, MN Nov 30-Dec 2 2001

Wisconsin Honey Producers Assoc. "Research Update" Oshkosh, WI Nov 1-4, 2001

Idaho Honey Industry Assoc. "Report of Current Research and its Application" Boise, ID Oct 26-27 2001

International Biennial Meeting of the Beekeeping Agriculture in Lazise (VR), Italy
"Hygienic Behavior of Honey Bees and Resistance to American foulbrood and chalkbrood" Oct 5-7 2001

Wisconsin Polk Co. Beekeepers Assoc. "Research Update" Amery, WI Sept 23.

MN Honey Producers Assoc. "Comparison of Lines of Bees Bred for Mite Resistance" Morton, MN July 19-21 2001

Kansas Beekeeping Association. "Bee Breeding and Selection" Tonganoxee, KS June 2 2001

North Central MN Beekeeping Assoc. "Research Update" Brainerd, MN June 18 2001

MN Fruit and Vegetable Growers Assoc. "Apple pollination" St. Cloud, MN Feb 2 2001

Wisconsin Cranberry School. Stevens Pt., WI "Economics of Pollination" Jan 9-10 2001
Minnesota Honey Producers Assoc "Research Update" Alexandria, MN Dec 3-5 2000

Iowa State Beekeeping Assoc. "Hygienic Behavior as a Defense Against American foulbrood and Varroa mites in Honey bee Colonies" Marshalltown, IA Nov 10-11 2000

Washington State Beekeepers Assoc. "Is Breeding for Hygienic Behavior Worth the Effort?" and "What goes on in a hygienic bees’ brain?" Tacoma, WA. Nov 2-4 2000

International Conference: Molecular Mechanisms of Disease Tolerance in Honey Bees, Prague, Czech Republic. "Mechanisms of American Foulbrood Resistance" (keynote speaker) October 17-19 2000

North American Section: International Union for the Study of Social Insects, Ozarks, Ark. Influence of colony genotypic composition on the performance of hygienic behavior in the honey bee. Oct 5-7 2000
North Dakota Beekeeping Assoc. "Research Update" Bismarck, ND Oct 13-14 2000

Bee Improvement and British Breeders Association (BIBBA) "Is Breeding for Hygienic Behavior Worth the Effort?" and "What goes on in a hygienic bees’ brain?" Sheffield, England, UK Sept 1-4 2000

Minnesota Honey Producers Assoc. "Varroa birth control" Willmar, MN. July 6-8 200

Institut für Landwirtschaftliche Zoologie und Bienenjunde der Universität, Bonn, Germany. "Neuroethology of Hygienic Behavior in Honey Bees" May 9 2000

2nd International Conference on Africanized Honey Bees and Bee Mites, Tucson, AZ. "Non-reproduction in Varroa jacobsoni" April 10-12 2000

Ontario Beekeepers’ Association, University of Guelph, Ontario. "Hygienic Behaviour as a Defense Against American foulbrood and Varroa mites in Honey bee Colonies" April 3-4 2000

Oberlin College, Oberlin Ohio. "Neuroethology of Hygienic Behavior in Honey Bees" Feb 23 2000

Ohio State University, Dept. Entomology, Columbus, Ohio. "Neuroethology of Hygienic Behavior in Honey Bees" Feb 21 2000

Apiary Inspectors of America, Gainesville, FL "Hygienic Bees vs. American foulbrood and Mites" Jan 19-21 2000

American Beekeeping Federation, Ft. Worth, TX "Effect of Fluvalinate Residue on Colony Performance" Jan 12-15 2000

Wisconsin Cranberry School – Stevens Point, WI. "Cranberry Pollination Biology" Jan 5-6 200

Association National des Eleveurs de Reines et des Centres d’Elevage Apicole (ANERCEA) – (French Bee Breeding Assoc.) Avignon, France. "Breeding honey bees for Mite Resistance" Nov 18-19 1999

Minnesota Honey Producers Association – Alexandria, MN "Queen Rearing and Breeding" Dec 2-4 1999

California State Beekeeping Association – San Diego, CA. "Research Update" Nov 9-11 1999

Wisconsin Honey Producers Association – Manitowac, WI. "Are there Varroa resistant bees in the world?" November 5-6 1999

North Dakota Beekeepers Association – Bismarck, ND. "Research Update" October 8 1999

Apimondia International Congress– Vancouver, Canada. "The potential for breeding varroa-tolerant honey bees" (keynote speaker, Plenary Session: "New Directions in Mite Management") Sept 12-17 1999

Project Outcomes

Recommendations:

Areas needing additional study

The most important area to pursue is the breeding program to combine the hygienic and SMR traits to maintain disease resistance while increasing the degree of mite resistance in one line of bees. We feel this combination has much potential for the beekeeping industry because both the hygienic line and the outcrossed SMR line performs well in beekeeping setting; they produce large amounts of honey, they are relatively gentle, easy to manage, and they winter well. Because of the problems in brood viability with the SMR x SMR colonies (SMR queens mated to only SMR drones) it is important to allow the SMR queens to mate with other drones. Having SMR queens mate with Hygienic drones is one solution; having HYG queens mate with SMR drones is another. We have identified 3 queens from each reciprocal cross that demonstrate good brood viability, hygienic behavior and mite resistance. It is very important to persist with the testing of these hybrids to develop a commercially viable line of bees that requires little to no antibiotic and pesticide treatment to survive. Beekeepers are losing their small arsenal of antibiotics and pesticides to control diseases and mites due to the development of resistance to the treatments. We feel with strong outreach efforts and good bee stock that is able to defend itself against diseases and mites, beekeepers will move to the more sustainable and healthy solution of using resistant stock rather than pushing for new antibiotic and pesticide registration. The timing is exactly right to continue our line of research, education, and outreach.

On a more basic level, another area that requires further study is in understanding the mechanism for the suppression of mite reproduction. Mites that do not reproduce are found in many bee colonies at a low level. While some mites do not produce any progeny, others produce only males, or produce progeny too late to mature. Non-reproduction is heritable trait (Harbo and Harris, 1999) but it is unclear how the bee suppresses the reproduction of the mite. Several researchers have investigated physiological aspects of this suppression, such as the possibility that some bees have lower hormone levels, so that the mite upon feeding on the hemolymph of the bee does not receive sufficient hormone to stimulate egg development (e.g., Rosenkranz et al., 1990). However, to date, this line of research has yielded contradictory results. Previous research on the behavior of the mite within a cell containing a worker pupa indicated that the mite has a very rigid behavioral repertoire while feeding and reproducing. The first 24 hours within the cell are critical for the initiation of mite reproduction. It could be that there are behavioral incompatibilities between some lines of bees and the mites. For example, during the first 30 hours, the bee larva must spin a cocoon of silk under the wax capped cell. If the mite cannot successfully track the movements of the larva, or is not able to feed sufficiently because it cannot find a feeding site during the spinning, it could lead to non-reproduction. We have done some preliminary work to explore this possibility by attempting to video record the movements of the bee larva and the mite during the first 30 hours after the mite enters a transparent cell. We will be requesting further grant money to pursue this line of research.

Information Products

Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.