Category Archives: 2015

Varroa mite control – what works ! By Dewey M. Caron

The pnwhoneybeesurvey received responses from 250 backyard beekeepers in 2015. Overall overwinter losses of individuals with either 8- or 10-frame Langstroth bee colonies was 27%; factoring in total backyarder losses for beekeepers entering winter with Langstroth, Top Bar, Warre, 5-frame nucs or other hive types was 29%. Our annual OSU survey of commercial and semi-commercial beekeepers (13 OR individuals maintaining some 60% of the estimated total colonies in the state) was 14.2%, somewhat below the commercial/semi-commercial beekeeper loss rate in the Pacific Northwest states of OR, WA and ID combined (=15.7%).The BIP national survey that included both backyarder and commercial beekeepers, reflecting survey responses from more backyard individuals but the majority of colonies were those of commercial beekeepers, reported a slightly lower overall loss of 23.2% . This is shown graphically as Figure 7 below.v1
Mite Monitoring
One hundred sixty three (163) individuals reported that they monitored for mites during some of the previous year (see for information on monitoring and when the monitoring was doneseparated by method of monitoring). The graph below shows the method used expressed as percent of individuals with number of individuals shown in ( ) within the graphic. One hundred individuals (37%) used sticky board mite drop, slightly over 100 (41% total) used visual inspections of either adult bees (54 individuals) or drone brood (55 individuals), while 45 individuals (17%) used sugar shake. Fourteen (14) individuals did an alcohol wash (5%) of total. The total is greater than 250 since
44% of responding individuals used more than one monitoring technique (both visual inspection methods were often checked for example).v2
We know the most reliable technique for examination of mite populations within a bee hive is via use of alcohol washing or powdered sugar shake. When we compared the individuals who used each technique (whether singly or in combination with another technique) and the reported loss by the same individuals, the result illustrates how significant monitoring with sugar shake was as this group had significantly lower overwintering losses (22%) compared to those who did not monitor (89 individuals – 31% loss) or used visual monitoring (29% and 31% loss rates -see graphic below). Those who checked sticky board also had significantly lower losses (22.5%). Individuals (14 total) who used alcohol washing did not show reduced losses, in part, because the variation among those 14 individuals was large.

Use of a Non-Chemical Control
We asked in the survey about control, both with a varroa control chemicals and via use of a non-chemical technique. In the options for non-chemical control, we received 406 responses from 75% of the individuals – 25% (49 individuals) did not indicate use of any of the choices nor fill in the other selection opportunity. Ninety-seven individuals (51%) ireported use of 2 (56 individuals) or 3 or more techniques (41 individuals). The graphic below shows the percent loss response for the alternatives offered, minus the 150 individuals (37%) of responses who checked use of screen bottom board (which is reported in a different report on the website – under Screen bottom boards.) Losses for each alternative are irregardless if they used only that technique alone or used it along with another/other methods.v4

There is no statistical difference between the data points. None were widely used. Individual selections varied from 49 individuals who checked nothing used to 21 individuals who said they used the technique of requeening. Numbers were relatively small and variation was large. The only value that was below the 27% average loss was use of small cell/natural comb (24% – most responses seemed to be the natural comb choice). Largest loss values were for requeening (36%) and brood cycle interruption (39%), the two techniques that are usually listed as viable, useful non-chemical controls. Why they are on the high end of the loss scale is unknown.
Chemical Control
For the users of 8 and 10 frame Langstroth hives, we compared the percent loss of individuals who used a chemical control for varroa mites (142 individuals) to those who did not. The loss rate of those using a chemical control were one-third as large as the overall group and were nearly double for those who did not use a chemical control. Results were statistically significant from the total loss of this group of 27%. v5
Examining individual choices (50 individuals reported use of more than one chemical) show use of three materials,resulted in significantly lower overwintering losses. Graph below. v6
Beekeepers have various options for Varroa control. The key to better overwintering is to monitor using sugar shake or alcohol wash to determine infestation level of a colony and then depending upon the season deciding on what might be an appropriate chemical or non-chemical technique to use to reduce mite populations. In this survey response we were unable to demonstrate the usefulness of non-chemical use to reduce overwintering losses. The BeeInformed Survey  2014-2015 preliminary results  does support our belief that non-chemical approaches can be useful and the Honey Bee Health Coalition website Tolls for Varroa Management guide Varroa management guide provides information on usefulness of an integrated non-chemical and chemical control approach to varroa mite population management.
Dewey M. Caron Sept 2015

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Nathalie Steinhauer1, Karen Rennich1, Kathleen Lee2, Jeffery Pettis3, David R. Tarpy4, Juliana Rangel5, Dewey Caron6, Ramesh Sagili6, John A. Skinner7, Michael E. Wilson7, James T. Wilkes8, Keith S. Delaplane9, Robyn Rose10, Dennis vanEngelsdorp1 1 Department of Entomology, University of Maryland, College Park, MD 20742 2 Department of Entomology, University of Minnesota, St. Paul, MN 55108 3 United States Department of Agriculture, Agricultural Research Service, Beltsville, MD 4 Department of Entomology, North Carolina State University, Raleigh NC 27695 5 Department of Entomology, Texas A&M University, College Station, TX 77843 6 Department of Horticulture, Oregon State University, Corvallis, OR 97331 7 Department of Entomology and Plant Pathology, University of Tennessee, Knoxville, TN 37996 8 Department of Computer Science, Appalachian State University, Boone, NC 28608 9 Department of Entomology, University of Georgia, Athens, GA 30602 10 United States Department of Agriculture, Animal and Plant Health Inspection Service, Riverdale, MD

The Bee Informed Partnership (, BIPin collaboration with the Apiary Inspectors of America (AIA) and the United States Department of Agriculture (USDA), is releasing preliminary results for the ninth annual national survey of honey bee colony losses. For the 2014/2015 winter season, a preliminary 6,128 beekeepers in the United States provided valid responses. Collectively, these beekeepers managed 398,247 colonies in October 2014, representing about 14.5% of the country’s estimated 2.74 million managed honey bee colonies1.

About two-thirds of the respondents (67.2%) experienced winter colony loss rates greater than the average self-reported acceptable winter mortality rate of 18.7%. Preliminary results estimate that a total of 23.1% of the colonies managed in the Unites States were lost over the 2014/2015 winter. This would represent a decrease in losses of 0.6% compared to the previous 2013/2014 winter, which had reported a total loss estimated at 23.7%. This is the second year in a row the reported colony loss rate was notably lower than the 9-year average total loss of 28.7% (see Figure 1 next page).

Beekeepers do not only lose colonies in the winter but also throughout the summer, sometimes at significant levels. To quantify this claim of non-winter colony mortality of surveyed beekeepers, we have included summer and annual colony losses since 2010/2011. In the summer of 2014 (April – October), colony losses surpassed winter losses at 27.4% (total summer loss). This compares to summer losses of 19.8% in 2013. Importantly, commercial beekeepers appear to consistently lose greater numbers of colonies over the summer months than over the winter months, whereas the opposite seems true for smaller-scale beekeepers. Responding beekeepers reported losing 42.1% of the total number of colonies managed over the last year (total annual loss, between April 2014 and April 2015). This represents the second highest annual loss recorded to date.Fig.1

Figure 1: Summary of the total colony losses overwinter (October 1 – April 1) and over the year (April 1 – April 1) of managed honey bee colonies in the United States. The acceptable range is the average percentage of acceptable colony losses declared by the survey participants in each of the nine years of the survey. Winter and Annual losses are calculated based on different respondent pools.

As in previous years, colony losses were not consistent across the country, with annual losses exceeding 60% in several states, while Hawaii reported the lowest total annual colony loss of ~14% (see Figure 2). Fig.2

Figure 2: Total annual loss (%) 2014-2015 by state. Respondents who managed colonies in more than one state had all of their colonies counted in each state in which they reported managing colonies. Data for states with fewer than five respondents are withheld.

This survey was conducted by the Bee Informed Partnership, which receives a majority of its funding from the National Institute of Food and Agriculture, USDA (award number: 2011-67007-20017).

1 Based on NASS 2015 figures 2 Previous survey results found a total colony loss in the winters of 24% in the winter of 2013/2014, 30% in 2012/2013, 22% in 2011/2012, 30% in 2010/2011, 32% in 2009/2010, 29% in 2008/2009, 36% in 2007/2008, and 32% in 2006/2007 (see reference list).  Lee, KV; Steinhauer, N; Rennich, K; Wilson, ME; Tarpy, DR; Caron, DM; Rose, R; Delaplane, KS; Baylis, K; Lengerich, EJ; Pettis, J; Skinner, JA; Wilkes, JT; Sagili, R; vanEngelsdorp, D; for the Bee Informed Partnership (2015) A national survey of managed honey bee 2013–2014 annual colony losses in the USA. Apidologie, 1–14. DOI:10.1007/s13592-015-0356-z  Steinhauer, NA; Rennich, K; Wilson, ME; Caron, DM; Lengerich, EJ; Pettis, JS; Rose, R; Skinner, JA; Tarpy, DR; Wilkes, JT; vanEngelsdorp, D (2014) A national survey of managed honey bee 2012-2013 annual colony losses in the USA: results from the Bee Informed Partnership. Journal of Apicultural Research, 53(1): 1–18. DOI:10.3896/IBRA.  Spleen, AM; Lengerich, EJ; Rennich, K; Caron, D; Rose, R; Pettis, JS; Henson, M; Wilkes, JT; Wilson, M; Stitzinger, J; Lee, K; Andree, M; Snyder, R; vanEngelsdorp, D (2013) A national survey of managed honey bee 2011-12 winter colony losses in the United States: results from the Bee Informed Partnership. Journal of Apicultural Research, 52(2): 44–53. DOI:10.3896/IBRA.  vanEngelsdorp, D; Caron, D; Hayes, J; Underwood, R; Henson, M; Rennich, K; Spleen, A; Andree, M; Snyder, R; Lee, K; Roccasecca, K; Wilson, M; Wilkes, J; Lengerich, E; Pettis, J (2012) A national survey of managed honey bee 2010-11 winter colony losses in the USA: results from the Bee Informed Partnership. Journal of Apicultural Research, 51(1): 115–124. DOI:10.3896/IBRA.  vanEngelsdorp, D; Hayes, J; Underwood, RM; Caron, D; Pettis, J (2011) A survey of managed honey bee colony losses in the USA, fall 2009 to winter 2010. Journal of Apicultural Research, 50(1): 1–10. DOI:10.3896/IBRA.  vanEngelsdorp, D; Hayes, J; Underwood, RM; Pettis, JS (2010) A survey of honey bee colony losses in the United States, fall 2008 to spring 2009. Journal of Apicultural Research, 49(1): 7–14. DOI:10.3896/IBRA.  vanEngelsdorp, D; Hayes, J; Underwood, RM; Pettis, J (2008) A Survey of Honey Bee Colony Losses in the U.S., Fall 2007 to Spring 2008. PLoS ONE, 3(12). DOI:10.1371/journal.pone.000407  vanEngelsdorp, D; Underwood, R; Caron, D; Hayes, J (2007) An estimate of managed colony losses in the winter of 2006-2007: American Bee Journal 147(7):599-603

Note: This is a preliminary analysis. Sample sizes and estimates are likely to change. A more detailed final report is being prepared for publication in a peer-reviewed journal at a later date.

Canadian Association of Professional Apiculturists Statement on Honey Bee Wintering Losses in Canada (2015) = 16.4%
The Canadian Association of Professional Apiculturists (CAPA) conducts an annual honey bee wintering loss survey using a set of harmonized questions based on national beekeeping industry profiles.Provincial Apiculturists collected survey data from beekeepers across Canada who own 362,949 honey colonies. This represents 50.8% of all colonies operated and wintered in Canada in 2014. The national average percentage of colony winter loss was 16.4%. Provincial averages ranged from 10.4-37.8%; the highest loss inOntario was a decrease of 34.8% compared to the 58.0% loss reported in 2013/14. Overall, the reported national colony loss is one of the lowest losses since 2006/07 and represents a decrease of 34.4% from 2013/14 winter losses.
Respondents reported considerable variation in identifying and ranking the top 4 possible causes of colony losses. Answers included starvation, weak colonies, poor queens, Nosema and weather conditions. Beekeepers also responded to questions on management of Varroa mites, Nosema and American foulbrood. Over 73% of beekeepers monitored Varroa infestation, the majority using controls used Apivar™, formic acid and oxalic acid for treatments. Despite monitoring Nosema infections less frequently, many beekeepers regularly used fumagillin to treat nosemosis.
Honey Bee Winter Loss in Canada since 2007
In Canada, winter loss shows a declining trend since 2010 (Fig 1). The winter losses were highest in 2007 to 2009 ranging from 29.0 – 35% (average 32.6%). From 2010 to 2015, losses ranged from 16.4 to 29.3% (average 23.8%).can9
It should be noted that the reported winter loss in 2014/2015 was in most of the provinces within the acceptable long term targeted winter loss by beekeepers. These reports of multi-year surveys provide evidence that Canadian beekeepers have been successfully addressing bee health issues, although beekeepers have access to few effective chemical products to control Varroa mite and Nosema. If resistance develops today to any of these products and alternative treatments are not
available or are still under development, beekeepers will suffer serious consequences. Ultimately, beekeepers must consider an integrated approach to maintain healthy bees. This approach is not only limited to pest management, but it includes proper nutrition, large healthy bee populations throughout the year, and reducing exposure to pesticides.
Losses of honey bee colonies over the 2014/15 winter – Preliminary results from Europe =17.4%
The honey bee research association COLOSS provided preliminary results of their international study of colony losses over the 2014-15 winter. Data were collected from 31 countries. Egypt, Russia and the Ukraine participated for the first time in this initiative, which is the largest and longest running international study of honey bee colony losses. In total 23,234 respondents provided overwintering mortality and other data of their colonies.

Collectively, all responding beekeepers managed 469,249 honey bee colonies. 67,914 of these colonies were dead after winter and an estimated 3 % of these colonies were lost because of unsolvable queen problems after winter. A preliminary analysis of the data shows that the mortality rate over the 2014-15 winter varied between countries, ranging from 5 % in Norway to 25 % in Austria, and there were also marked regional differences within most countries. The overall proportion of colonies lost (including colonies with unsolvable queen problems after winter) was estimated as 17.4 %, which was twice that of the previous winter.

The protocol used to collect this COLOSS data has been internationally standardized to allow comparisons and joint analysis of the data. A more detailed analysis of risk factors calculated from the whole dataset , as well as further colony loss data from other countries, will be published later in the year.

International Data Coordinator for the COLOSS Monitoring and Diagnosis Working Group Romée van der Zee from the Dutch Centre for Bee Research says: “North European countries have traditionally had lower losses,compared to west and central European countries. This can partly be explained by the later start of the breeding season of their honey bee colonies due to low temperatures in March/April, as was the case in 2014. This later start limits the number of brood cycles of the varroa mite, one of the main parasites of honey bees. However, honey bee colony loss is a multifactorial problem. There is clearly also a variation in losses between areas, which is not dependent on the varroa mite. One of the main aims of our network is to identify and describe such areas.”can10
Sources: BIP

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Screen Bottom Boards by Dewey M. Caron

Screen Bottom Boards (SBB) have a number of uses in our bee stewardship. They are widely substituted for a solid bottom board.  A 1939 Delaware beekeeper removed his solid bottom and left his colony open at the bottom, which he termed bottomless beekeeping. There truly is nothing “new” in our beekeeping practice of using a screened bottom on hives. Although many beekeepers use SBB to control varroa, BIP and PNW surveys clearly point out they are not a very effective varroa mite control tool.

In our national BIP surveys, fully 95% of respondents indicate they have modified the colony bottom board and now use a screen bottom board. sbb1 Our PNW Honey Bee Survey also asked respondents about screen bottom board use. Among Oregon and Washington hobbyist (backyarders or small-scale beekeepers), 79% of the 250 respondents said they used screened bottoms; 66% used them on all their hives with the remaining 13% using them on a percentage of their hives (See figure right).

Comparing overwinter loss percentage, there was no difference for the 21% who did not use SBB (27% loss rate , same as tsbb2he overall 250 respondent base) compared to the79% who did (25% middle column in left graphic  – column on right of graphic is overall loss rate for those beekeepers using either 8-frame or 10 frame Langstroth hives – when the data for individuals who used other hive types besides Langstroth is included, the overall overwinter loss rate for backyarders was 29%).

We also asked whether they blocked colony SBBs during the winter. The majority (51%) left them open over the winter period sbb3(never response). 19% sometimes blocked them and 31% said they closed them (always response) during the winter (see graphic right). When we examined winter losses for this response, there was no statistical dfference in loss, although the trend was for lower losses when the SBB were closed  (24% vs 31%).

As stated above, SBB are not an effective mite control tool, although most beekeepers state they are using them for that reason. In our PNW survey, respondent beekeepers who said they used bottom boards as a non-chemical treatment option for varroa mites, had no statistical improvement in survivability.  Langstroth 8-frame beekeepers who listed SBB use, entered winter with 97 colonies losing 25 by the spring (=25% loss rate) and Langstroth 10-frame beekeepers entered winter with 596 colonies of which 440 survived ( =26% loss rate); other hive types included in the survey (5-frame nucs, top bar hives or Warre hives) do not easily lend themselves to bottom modification with screening, although some individuals with such hives may use a partial bottom screen in place of a solid bottom.

With our Bee Informed National survey (, use of SBB did not improve winter survival rate in any of our survey years when we directly compared their use with loss rates. However in survey year 2013-2014, northern beekeepers did have about a 10% decrease in losses when SBB were used compared to southern beekeepers. Experimental studies on SBB and mite population levels show either no or this slight ~10% improvement in reducing mite population levels when SBB are used.

So what can SBB do to benefit our bees?

Using a screen bottom aids greatly in hive ventilation. sbb4 It can be used with upper entrances at the covers or with ventilation ports added to hive bodies. Air circulation for better ventilation can be further aided by pushing the outer frames inward a bit to allow air circulation upward between the outer frame and box wall. Heavy burr and brace combs, sometimes due to incorrect bee spacing between the hive boxes, when both the bottom bar and the dropping of the top bars below the rim creates a ½ inch of larger space, and heavy propolis use in the fall, may reduce good air circulation in the boxes.

During winter, beekeepers at more northerly locations or higher elevations often close or reduce the screen opening beneath their colonies. It is not advisable to have wind blowing into the bottom of a winter colony but an air space beneath the colony, with screen bottom board left open, is not detrimental to colony wintering. The dead air space and moderating soil temperatures may be helpful. Often this dead space beneath a screened bottom can be created with hive stand configuration.

Another advantage of a screen bottom board is that it provides for a convenient garbage pit to remove debris and fallen mites from a colony. The original Langstroth hive had such a feature but it was discontinued when the hive construction was simplified. They were thought to promote wax moth with the design Langstroth used.

Screen Bottoms may offer some improvement for some beekeepers, particularly where winter confinement period is long and when mite populations are lower. In is not clear if this improvement is due to mites alone or to the other effects a screen vs closed bottom may have on colony survivability (see below). As regards varroa mites they should be considered a tool that may reduce winter losses when used in combination with other mite control treatments and tools.

August 2015 Dewey M. Caron

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Dr. Caron’s discussion on fall feeding

Feeding Fall Colonies     by Dewey M. Caron

Feeding bees in the fall is unquestionably a way to make the fatbeedifference in whether a colony survives overwinter or not.  When colonies are light on food stores, feeding a heavy sugar syrup or not extracting stored honey can improve winter survival. It is the best management option to insure the proper fall configuration and promote raising FAT fall bees. To raise Fat bees the colonies need to be FAT with honey.

honeystoresFor improved wintering success, it is important to ensure the brood nest is situated low in the colony before fall ends. Ideally, an ample ceiling of fully-ripened honey will be stored above the brood nest enabling bees to eat their way upward through the overhead stores as winter progresses (See Diagram left). If colony brood nest is still sitting high in the colony mid-Aug/early September, I recommend beginning supplemental feeding soon.

Should honey be fed? Honey can be fed to fall colonies if you know it is from colonies free of disease, particularly American Foul Brood. The easiest way to feed honey is to redistribute honey from colonies that possess heavier stores to those light on stores. Do not rob colonies too heavily when removing honey to extract. You can remove and store honey-filled frames in the freezer and make your extracting decision later in fall or put honey supers on one colony if you wish to treat other colonies for mites.

If you have “junk” honey (honey you don’t wish to extract or honey that has crystallized in the combs), score the cappings to make a “mess” to stimulate the bees to move it into their storage pattern. You can place such frames above the inner cover, or on top of the colony. Some people advise putting such honey beneath the lowest box on the bottom board but this will require some heavy lifting. If you have liquid honey to feed, dilute it with warm water before putting into syrup feeder (honey is best fed in a closed feeder to avoid any robbing by bees from other colonies).

Does it make a difference to feed or what sugar is fed? Data collected last year at PNW Honey Bee Survey ( losssuggested there were heavier loses of individuals who did no feeding of their colonies (33% loss rate) compared to those who did feed (27%) (See graph right). There was no difference in improvement in loss percentage whether sugar syrup (sucrose as cane or beet sugar mixed with water), corn syrup, drivert, fondant or frames of honey were fed (see graph below).  For latest fall and earliest spring  feedings, generally a clean, non-contaminated sugar is recommended.  Some individuals do not care to feed corn syrup (high fructose syrup) nor beet sugar (it comes from a GMO crop). During the active season, sugars with contaminants, (darker sugars, syrups with corn syrup, candy liquefied into syrup, etc) seem to be OK.carbs There is no indication that feeding converted sugars (sucrose already reduced to mixture of the simpler sugars glucose and fructose) offers any digestive advantage to honey bees.

Fall feeding of protein does not make for a larger colony nor improve survival. Bees apparently do not store the artificial diet material but if there is a lack of pollen stores (i.e. bee bread) in a colony, fall protein feeding can help insure FAT bees. Feeding pollen patties or dry protein material in an outside feeder does help boost growing colonies and extend the pollen availability. Pollen is not always reachable in early spring with rain and/or cooler temperatures inhibiting flight.

What is best way to feed liquid syrups? Different individuals have different ways to feed and offer different sugar sources. Basically the BEST way to feed is the one you find useful and fits within your budget. You can buy expensive feeders or be inventive and recycle materials to use as feeders. Many simply put the syrup into a recycled jar or can that has a removable lid with tiny holes punched in the lid. One or more feeders can be placed above the inner cover hole, with or without a piece of screen material, or directly onto the top bars of the top box. Three tin cans with removable lids are shown in diagram below to right directly on top of frames. An empty shell should be placed around the feeder and the lid properly weighted to avoid the empty box becoming displaced. It is easy to check and refill/replace such containers when the bees have taken down the contents.

Some feed bees in a common feeder in the apiary (feed lot feeding). I don’t like this method and it isn’t a good method for urban beekeepers since it can lead to a cloud of bees at the feeding site. It seems the strongest colonies are the ones that collect most of the syrup, not necessarily those that need it the most.

feed1I like to drill a hole the size of a plastic jar and put the feeder jar outside the lid (as shown to left).  feed2I can remove an empty jar and replace it with a filled jar before the bees have a chance to occupy the space of the hole. External feeders (shown right) are black to cause less heating of the syrup. Such feeders are available from bee supply companies.

A popular way larger-scale beekeepers use to feed colonies (rather than feed-lot feeders) is with an internal feeder. feed3They purchase or make their own Division Board feeders and place them at the edge of the box, replacing one or two regular frames (Figure to the left shows a homemade feeder at left of brood box). Most of the larger-scale beekeepers have a tank on their vehicle and a hose delivery system to refill the feeders by simply moving aside the cover and/or boxes on top of the internal feeders and then quickly refilling the feeder. This is less useful for smaller-scale beekeepers because it necessitates opening the colony and without a convenient liquid delivery system refilling can be tedious.  It is advantageous as bees will readily utilize the syrup in such feeders. They should be equipped with a ladder so bees can easily enter and exit and avoid accumulating dead bodies at the bottom.

Feed heavy syrups in the fall. We do recommend that the syrup be mixed heavy in fall feedings. This is to stimulate storage of the material vs. stimulating brood rearing. If you have liquid honey to feed, dilute it and feed in a container feeder within the hive.  Be careful when feeding in fall or during a drought so that you do not promote robbing behavior. Reduce entrances and avoid spilling honey/syrup outside of colonies.

feed4In Oregon you should seek to feed colonies the heavy syrup before the fall rainy season appears. After rains become common, we recommend switching to a dry sugar so as not to add to moisture stress to the colonies. Granulated sugar can be fed in a top rim such as a Vivaldi board or simply poured on the inner cover as shown in left photo. feed5An alternative is to make a sugar candy and place it above the inner cover hole. Alternately you can harden the candy into a rim and then position the candy above the top bars as shown in right photo. Warm moist air from the cluster below will make a slurry of the candy above the bees (or at the oval opening if inner cover is used) allowing the bees to access the candy as they need it. A good alternative is to feed more expensive fondant sugar – it absorbs moisture and will not become as hard enabling the bees to take it as they need it. These forms of feeding don’t add additonal mositure stress to the winter colony. Our BeeInformed survey has shown that feeding dry sugar or candy improved ovewintering success.

Should food stimulants (such as Honey-Bee-Healthy, Amino Acid boosters, probiotics, etc) be added to sugar syrups when feeding in the fall?  Although they can be good additions to entice the bees into quickly emptying feeders and stimulate healthy colonies, some advocate avoiding adding a food stimulant in the fall. If you are debating the value of such additives I suggest you try splitting your colonies into two lots, feeding one and not the other and see if you see a difference. New additives seem to frequently come on the market, but most, adapted from feeding other livestock, have not been extensively or independently tested for effectiveness or potential harmful effects.

Should you add vinegar or an acid to syrup to bring the pH down to around 4.7?  At one time, using additives to avoid sugar spoilage and mold growth in feeders was the standard recommendation. Those who feel it important to create a more acidic syrup, thought to better duplicate flower nectars (which have a wide pH range depending upon the flower and plant growing conditions) may help the bees intestinal function. Avoid toxic sugars (such as milk sugars lactose and galactose) and avoid salt as a higher salt content quickly turns bees off.

Will feeding sugar in the fall make a difference? Results from the PNWhoneybeesurvey suggested those who didn’t feed lost more colonies than those who did feed. The best advice, try it, you might like the improvement in overwintering in your colonies.

Dewey Caron August 2015

Download PDF of this article here Feeding Fall Colonies

To Use or Not To Use Screened Bottom Boards – That is the question

Question emailed after a club meeting…

I was at your presentation last Monday night in Olympia.  I was the one that asked if you could phrase a question in your survey about whether the keeper using a screen bottom board leaves the sliding board in or has an open screen floor.  The reason I asked is because after using screen bottom boards for years, I discovered, in my apiary, that an open screen floor is a death sentence for a colony in the Pacific Northwest. The result that the loss rate was about the same for using SBB as it was for not using them, I really believe needs clarification in details.

Perhaps questions along the lines of;

If you use SBB’s what best describes your management style with them? I have open screen floors. I have sliding boards/enclosed SBBs. I use my SBB’s in correlation with an IPM program.

Response by Dewey

We really do have a limitation on the numbers of questions we can put on the survey. You pose some interesting questions however and we will consider some revisions to clarify for next survey year.

I really think our survey this year does however point out that whether one uses a SBB and whether one leaves it open over the winter or closes it, makes NO DIFFERENCE at least with respect to overwinter losses. This is not to dismiss your experience. What works for you and your apiaries consistently please don’t change because others might not do it the same way. If you find an open bottom screen is detrimental, “a death sentence”, then don’t change back to one.

For others however the result was different. In our 2015 survey when we asked the question on SBB use as a non-chemical treatment we found for those 150 individuals. For Langstroth 8 frame hives 97 fall colonies had 73 still alive in the spring =25% loss rate and for those with Langstroth 10 frame hives of 596 fall colonies there were 440 alive the next spring  = 26% loss rate. The overall loss rate was 27% with a 3 % rate of variation. This means the Langstroth 8 and 10 frame losses fell within the loss rate and were not significantly lower, i.e. no real difference between 25% or 27%.

When I compared the loss rate for those 33 individuals who said they did not use screen bottom boards, their loss rate was 25% and for those individuals who said they had a SBB on 100% of their colonies (97 individuals) the loss rate was 27%. There is no significant difference between 25% and 27% . There were a small number who used SBB on less than 100% of their colonies but I did not do that analysis as there were too few numbers to create a significant result.

Finally I did ask indirectly about what you were interested in learning. I asked in survey if SBB were closed in the winter (the never response) or they were always left open. Those who checked never (107 total) had 24% loss, those who checked sometimes had 27% loss, and those who closed them in winter (55 totals) had 31%, the heaviest loss.  Although this is a trend, there is no statistical difference in these numbers, i.e. 31%-27% =25%.

So in retrospect I think I did ask the three questions you had except I didn’t specify if the screens had sliding boards or some other way of closing,(for those who did close. This result agrees with our larger data base of BIP – no difference evident in winter survival whether the bottom is a screen or solid bottom board or whether the board is open for part of the year. We do recommend it be closed when fumigating with Apiguard or Api Life Var – at least for that first week.