Honey Bee Colony Losses 2018-2019: Preliminary Results

Bee Informed.jpg

JUNE 19TH, 2019

Note: This is a preliminary analysis. Sample sizes and estimates are likely to change. A more detailed state-specific report, as well as a manuscript for submission to a peer-reviewed scientific journal, will follow at a later date. 

The Bee Informed Partnership (BIP; http://beeinformed.org) recently conducted the 13th annual survey of managed honey bee colony losses in the United States. This past year, 4,696 beekeepers collectively managing 319,787 colonies as of October 2018 provided validated colony loss survey responses. The number of colonies managed by surveyed respondents represents 11.9% of the estimated 2.69 million managed honey-producing colonies in the nation (USDA, 2018).

During the 2018-2019 winter (1 October 2018 – 1 April 2019), an estimated 37.7% of managed honey bee colonies in the United States were lost (Fig. 1). This loss represents an increase of 7 percentage points compared to last year (30.7%), and an increase of 8.9 percentage points compared to the 13-year average winter colony loss rate of 28.8%. This year’s estimate is the highest level of winter losses reported since the survey began in 2006-2007.

Similar to previous years, backyard beekeepers lost more colonies over the winter (39.8%) compared to sideline (36.5%) and commercial (37.5%) beekeepers. Backyard, sideline, and commercial beekeepers are defined as those managing 50 or fewer colonies, 51 to 500 colonies, and 501 or more colonies, respectively.

Our survey also asked what level of winter loss would be acceptable by beekeepers. Interestingly, this revealed an increase from 20.6% last year to 22.2% this year, which is much greater than the 11-year average of 17%. This increased acceptable loss may indicate that beekeepers are more realistic or pragmatic in their expectations of colony losses. Even with a higher acceptable loss, sixty-two percent of responding beekeepers lost more colonies than the level deemed acceptable.

During the summer 2018 season (1 April 2018 – 1 October 2018), an estimated 20.5% of managed colonies were lost in the U.S. This level is slightly higher (3.4 percentage points) than the previous summer’s colony loss estimate of 17.1%, but is on par with the summer loss average reported by beekeepers since 2010-2011 (20.5%), when summer losses were first recorded by the BIP.

For the entire survey period (1 April 2018 – 1 April 2019), beekeepers in the U.S. lost an estimated 40.7% of their managed honey bee colonies. This is similar to last year’s annual loss estimate of 40.1%, but slightly higher (2.9 percentage points) than the average annual rate of loss reported by beekeepers since 2010-11 (37.8%).

We note that loss rate for each period was estimated by identifying the total number of at-risk-colonies that died, and that annual loss rate was not estimated by summing the individual summer and winter loss rates. This year’s state-specific loss rates will be added to previous years’ results on the BIP website shortly (https://bip2.beeinformed.org/loss-map/).

Total US Colony Loss.jpg

Fig 1. Total winter colony loss rate in the United States across years of the Bee Informed Partnership’s National Honey Bee Colony Loss Survey (yellow bars; 1 October – 1 April)1. Total annual loss estimates (orange bars) include total winter and summer (1 April – 1 October) losses; the latter has been estimated since 2010-2011 only. The acceptable winter loss rate (grey bars) is the average percentage of acceptable winter colony loss declared by the survey participants in each year of the survey.

 1Previous survey results estimated total winter colony loss values of 31% in the winter of 2017-18, 21% in 2016-17, 27% in 2015-16, 22% in 2014-15, 24% in 2013-14, 30% in 2012-13, 22% in 2011-12, 30% in 2010-11, 32% in 2009-10, 29% in 2008-09, 36% in 2007-08, and 32% in 2006-07 (see reference list).

https://beeinformed.org/results/2018-2019/

Nation's Beekeepers Lost 33 Percent of Bees in 2016-17

May 26, 2017

Nation's Beekeepers Lost
33 Percent of Bees in 2016-17


Annual losses improved over last year;
winter losses lowest in survey history

Beekeepers across the United States lost 33 percent of their honey bee colonies during the year spanning April 2016 to April 2017, according to the latest preliminary results of an annual nationwide survey. Rates of both winter loss and summer loss--and consequently, total annual losses--improved compared with last year.

Total annual losses were the lowest since 2011-12, when the survey recorded less than 29 percent of colonies lost throughout the year. Winter losses were the lowest recorded since the survey began in 2006-07.

The survey, which asks both commercial and small-scale beekeepers to track the survival rates of their honey bee colonies, is conducted each year by the nonprofit Bee Informed Partnership in collaboration with the Apiary Inspectors of America. Survey results for this year and all previous years are publicly available on the Bee Informed website.

"While it is encouraging that losses are lower than in the past, I would stop short of calling this 'good' news," said Dennis vanEngelsdorp, an assistant professor of entomology at the University of Maryland and project director for the Bee Informed Partnership. "Colony loss of more than 30 percent over the entire year is high. It's hard to imagine any other agricultural sector being able to stay in business with such consistently high losses."

Beekeepers who responded to the survey lost a total of 33.2 percent of their colonies over the course of the year. This marks a decrease of 7.3 percentage points over the previous study year (2015-16), when loss rates were found to be 40.5 percent. Winter loss rates decreased from 26.9 percent in the previous winter to 21.1 percent this past winter, while summer loss rates decreased from 23.6 percent to 18.1 percent.

The researchers noted that many factors are contributing to colony losses, with parasites and diseases at the top of the list. Poor nutrition and pesticide exposure are also taking a toll, especially among commercial beekeepers. These stressors are likely to synergize with each other to compound the problem, the researchers said.

"This is a complex problem," said Kelly Kulhanek, a graduate student in the UMD Department of Entomology who helped with the survey. "Lower losses are a great start, but it's important to remember that 33 percent is still much higher than beekeepers deem acceptable. There is still much work to do."

The number one culprit remains the varroa mite, a lethal parasite that can easily spread between colonies. Mite levels in colonies are of particular concern in late summer, when bees are rearing longer-lived winter bees.

In the fall months of 2016, mite levels across the country were noticeably lower in most beekeeping operations compared with past years, according to the researchers. This is likely due to increased vigilance on the part of beekeepers, a greater availability of mite control products and environmental conditions that favored the use of timely and effective mite control measures. For example, some mite control products contain essential oils that break down at high temperatures, but many parts of the country experienced relatively mild temperatures in the spring and early summer of 2016.

This is the 11th year of the winter loss survey, and the seventh year to include summer and annual losses. More than 4,900 beekeepers from all 50 states and the District of Columbia responded to this year's survey. All told, these beekeepers manage about 13 percent of the nation's estimated 2.78 million honey bee colonies.

The survey is part of a larger research effort to understand why honey bee colonies are in such poor health, and what can be done to manage the situation. Some crops, such as almonds, depend entirely on honey bees for pollination. Honey bees pollinate an estimated $15 billion worth of crops in the U.S. annually.

"Bees are good indicators of the health of the landscape as a whole," said Nathalie Steinhauer, a graduate student in the UMD Department of Entomology who leads the data collection efforts for the annual survey. "Honey bees are strongly affected by the quality of their environment, including flower diversity, contaminants and pests. To keep healthy bees, you need a good environment and you need your neighbors to keep healthy bees. Honey bee health is a community matter."


This summary chart shows the results of an 11-year annual survey that tracks honey bee
colony losses in the United States, spanning 2006-2017. Credit: University of Maryland/BeeInformed Partnership

How the Varroa Mite Co-Opts Honey Bee Behaviors to Its Own Advantage

Entomology Today    By Entomology Today   May 10, 2017

While the Varroa destructor mite is not a highly mobile insect on its own, it takes advantage of the behaviors of honey bees in managed beekeeping settings to spread. In particular, bee colonies in close proximity to each other and less swarming allow mite populations to grow, according to new research. (Photo credit: Scott Bauer, USDA Agricultural Research Service, Bugwood.org)

As the managed honey bee industry continues to grapple with significant annual colony losses, the Varroa destructor mite is emerging as the leading culprit. And, it turns out, the very nature of modern beekeeping may be giving the parasite the exact conditions it needs to spread nearly beyond control.

In an article published yesterday in Environmental Entomology, researchers argue that the Varroa mite has “co-opted” several honey bee behaviors to its own benefit, allowing it to disperse widely even though the mite itself is not a highly mobile insect. The mite’s ability to hitchhike on wandering bees, the infections it transmits to bees, and the density of colonies in managed beekeeping settings make for a deadly combination.

“Beekeepers need to rethink Varroa control and treat Varroa as a migratory pest,” says Gloria DeGrandi-Hoffman, Ph.D., research leader and location coordinator at the U.S. Department of Agriculture-Agricultural Research Service’s Carl Hayden Bee Research Center in Tucson, Arizona, and lead author of the research.

In the wild, bee colonies tend to survive despite Varroa infestations, and colonies are usually located far enough apart to prevent mites from hitching rides to other colonies on foraging bees. Wild bee colonies’ natural habit of periodically swarming—when the colony grows large enough that a portion of its bees splinter off to create a new colony elsewhere—also serves as a mechanism for thinning out the density of mite infestations and their associated pathogens. In managed honey bee settings, though, these dynamics are disrupted, DeGrandi-Hoffman says. Colonies are kept in close proximity, and swarming is prevented.

DeGrandi-Hoffman, USDA-ARS colleague Henry Graham, and Fabiana Ahumada of AgScience Consulting, conducted an 11-month study of 120 honey bee colonies in one commercial bee operation, comparing those treated with mite-targeting insecticide (miticide) in the spring and fall with those treated only in the fall, and they found no significant difference in the results: more than half of the colonies were lost across the board. This aligns with what has been seen by beekeepers and researchers alike in recent years: Varroa populations continue to grow even after being treated with effective miticides. But why? The answer may be in its dispersal mechanisms.

The researchers also conducted mathematical simulations of Varroa mite population dynamics to examine the effects of both migration of foragers between colonies and swarming. When bees can wander into other colonies—either to “rob” them of their honey or because they’ve simply lost their way—Varroa populations across colonies climb. Likewise, prohibiting colonies from splintering periodically via swarming also leads mite populations to rise.

In the wild, DeGrandi-Hoffman and her colleagues note, driving a colony to collapse is against Varroa mites’ own interest; if the colony dies, the mites die with it. But in commercial beekeeping settings, increasing infestation of a colony activates the dispersal mechanisms the mites need to spread. Weakened foragers are more likely to wander to other colonies, and weakened colonies are more likely to see foragers from healthy colonies visit to rob them of honey. In both cases, mites can hitch a ride from one colony to another.

It all adds up to a critical point for managed honey bee industry. The researchers cite the need for new integrated pest management strategies to treat Varroa destructor as a migratory pest, as well as for further research into the specifics of Varroa dispersal.

“Colony losses in the U.S. are at unsustainable levels for commercial beekeepers. These beekeepers supply colonies for the pollination of crops that represent one-third of U.S. agriculture and are essential components of heart healthy and cancer-prevention diets,” says DeGrandi-Hoffman. “This research provides evidence that the tried and true ways of controlling Varroa are no longer feasible, and that new methods that are designed for control of a migratory pest are required.”

https://entomologytoday.org/2017/05/10/how-the-varroa-mite-co-opts-honey-bee-behaviors-to-its-own-advantage/

Read More:
Are Dispersal Mechanisms Changing the Host–Parasite Relationship and Increasing the Virulence of Varroa destructor (Mesostigmata: Varroidae) in Managed Honey Bee (Hymenoptera: Apidae) Colonies? “Are Dispersal Mechanisms Changing the Host–Parasite Relationship and Increasing the Virulence of Varroa destructor (Mesostigmata: Varroidae) in Managed Honey Bee (Hymenoptera: Apidae) Colonies?”  Environmental Entomology

Queen Replacement: The Key to Prevent Winter Colony Losses in Argentina

International Bee Research Association - IBRA   November 24, 2016

In recent years extensive losses of honey bee colonies have led to surveys of beekeepers, with much information now coming from Europe and north America. Much less information is available about colony losses elsewhere. Now, in a new paper published in the Journal of Apicultural Research, Agostina Giacobino and colleagues at the Instituto Nacional de Tecnología Agropecuaria, Rafaela, Argentina describe a survey of Argentinian colony losses during the 2013-14 winter.

Varroa mite infestation, colony strength, and winter colony losses were evaluated in 62 apiaries distributed in four different regions in east-central Argentina. Data regarding management practices in each apiary were also collected by means of a questionnaire. The key result was that beekeepers who reported replacing less than 50% of the queens in their apiaries each year showed higher winter losses than apiaries who replaced more than 50% of their queens. Even considering that the winter colony losses can be explained by a complex interaction of factors, requeening appears as one of the most important management practices to reduce this phenomenon in Argentina.

The article is available here (free to view): http://www.tandfonline.com/…/…/10.1080/00218839.2016.1238595

IBRA Members taking the JAR option have access to all other papers in issue 55(4), and also have full access to all articles in the Journal of Apicultural Research back catalogue to Volume 1 in 1962. You can join IBRA here: http://www.ibrabee.org.uk/2013-05-01-02…/2014-12-12-12-06-01