Notes from Dewey – March 2024

by Dewey M. Caron, Communications and Content Specialist for the Oregon Master Beekeeper Program

Hangry bees

Walsh, Liz, 2023. Hangry bees: Pollen deprivation affects temper in Pol-line honey bees (Apis mellifera). 2023 ABRC Bee Culture April 2023.  DOI:

The American Association of Professional Apiculturists (AAPA) hosted its annual meeting, the American Bee Research Conference (ABRC), in Jacksonville, Florida January  2023 in conjunction with the American Beekeeping Federation’s annual convention. One of the 50 talks that piqued my interest was by Liz Walsh of the USDA Bee Lab in Baton Rouge. Having come up to the Florida meeting from Bolivia, where the family keeps colonies of Africanized bees, I am very familiar with defensive bees.  the Pol Line bee developed at the Baton Rouge lab, favored by commercial beekeepers, is sometimes described as more defensive than other bee lines.

In this study, pollen dearth was simulated by utilizing pollen traps on colonies, half of which collected pollen and half of which were kept closed. When aggression assays were conducted, the colonies deprived of pollen were found to be more defensive (“hangry”) than non-pollen deprived colonies in the same beeyard. Foragers were collected from these colonies on a weekly basis throughout the five week experiment and the expression of 4+ genes associated with temperament were examined. Regardless of genetic background, the environmental stimulus of pollen dearth leading to nutritional stress was found to play a pivotal role in honey bee temperament. It confirms our anecdotal observations that when we trap pollen our Africanized bee colonies become even less manageable than normal.

News flash: Beekeeping is America’s 2nd Favorite Hobby

Americans are turning towards eclectic hobbies. Individuals search for activities such as aquarium keeping, home brewing, beekeeping, mushroom cultivation, and letterboxing. A survey of 3,000 adults to gauge shifting trends in interests and hobbies for the New Year Aquascaping or aquarium keeping emerged as the most popular with beekeeping the 2nd most popular.  For Oregonians surveyed beekeeping was #1. The report describes beekeeping as “…being a guardian of a tiny, buzzing kingdom, where you get to don a cool suit and peek into the fascinating world of honeybees. It’s not just about getting your own delicious honey (though that’s a big plus!), it’s also about helping these little pollinators thrive, which in turn brightens up your garden. What makes it particularly appealing is the deep connection it fosters with the natural world, allowing hobbyists to play a direct role in supporting the health and productivity of these essential pollinators….. a hands-on experience that is both educational and therapeutic.”  We couldn’t agree more.,and%20maintaining%20intricate%20underwater%20ecosystems

Photo: Libby Ashfield Rice’s backyard bees Bend

Looking at bees

Our bee colonies live in man made (Langstroth hive) and natural dark cavities. Beekeepers need to open (invade) the dark, smelly hive and disrupt our bees to see what is going on in their home. During the winter, opening a hive can cause more harm than good. Weather may not always cooperate when we want to look at our bees. Too much opening can be harmful. It takes a day or more for bees to recover from our hive invasion.

Watching entrance activity can provide some clues about what is happening inside, except when flight is not possible due to temperature/ weather conditions. Robbing, drifting and orientation flights can fool us. Bearding on the outside of the hive might mean temperature stress or crowding? Hefting colonies can give us some information on their stores/strength. Various weighing devices provide a more accurate assessment of store consumption. Examining the discharge of dead bees, and/or examining cappings (and additional debris) dropping to the debris board (if you use screened bottom boards) can offer some clues on what is happening within. A thermal camera can help us determine if the winter colony is dead or alive and temperature sensors (depending upon positioning) can help make the same determination. Tapping on a colony when the bees are confined within can reassure us they are alive.

In the February ABJ I wrote about how maintaining an Observation hive is an alternative to allow us to check on our bees. [Observation Hives add fun to beekeeping. Amer Bee Jour. Feb 2023. Pages 165-167.] We can learn and experience what they are doing without opening the hive. We might see how they are progressing in the season. And we can do it all from the comfort of our home, garage, outbuilding or wherever we establish the observational unit. The article is not so much a “how to” but “why we should.” I reference the how to in Frank Lintons book The Observation Hive Handbook. And for clues to help identify what we might observe looking at the bees in an observation hive the booklet Hive Tour by 2 Franks, Frank Linton and Phil Frank.

Mite control

We are accustomed to the use of essential oils for mite control. Currently only thymol (Apiguard) or APiLifeVar (primarily thymol with eucalyptus, menthol and camphor) are available as formulated, registered products. To kill mites we need highly concentrated compounds, whereas in our own health and/or to spice up our  foods we use smaller, less concentrated amounts. Lab tests have demonstrated that several essential oils have potential miticide qualities. In one publication of lab tests, peppermint, manuka, oregano, litsea, carrot, and cinnamon oils seem to be better for mite control than thymol. [Hýbl, Marian, et. al. 2021. Evaluating the Efficacy of 30 Different Essential Oils against Varroa destructor and Honey Bee Workers (Apis mellifera). Insects 2021, 12(11), 1045;]  Field testing with full-sized colonies have not always been consistent. Two significant factors that leads to variability are ambient temperature and relative humidity. The rate of vaporization of essential oils (and also organic acids) can negatively affect the exposure of the mites to these products, crucial for successful mite control.

One field test was a Guelph University , Ontario, Canada experiment of the efficacy of three natural compounds continuously delivered to hives using three application methods over a 4-week period in 24 Buckfast colonies (6 per treatment) beginning September 15th.  The three tests, along with a control were:  A rapid release mixture of 7% oregano and clove oils in an ethanol-gelatin solution applied as impregnated absorbent pads (estimate was 1 g release of each oil), continuous release of Oregano oil alone delivered using 2 electric vaporizers (estimated 0.99 g release /day) and (slow release) 2% Oxalic acid in a heavy sucrose solution impregnated in cardboard (estimate was each treatment was 5 g of Oxalic acid).

The results showed no differences in mite mortality (determined via sticky boards) between control and treatments of oxalic acid and oregano essential oil. The bulk of the mites  were killed in the first 2 weeks in the oregano oil colonies compared to the last 2 weeks in colonies of the other treatments. The authors concluded their results demonstrated “the importance of continuously releasing natural miticides can achieve safe and high rates of mite control in hive’  and that “oregano oil may be an effective miticide against varroa mites.”

What does this experiment demonstrate?  Continuous release of oregano oil was as effective as slow release oxalic acid. We know we need more tools to effectively fight varroa mites. Thinking “outside the box” and funding to enable experimentation on other possible miticides and miticide delivery methods is sorely needed. NOTE: Such testing is complex and costly and is only a first step toward possible approval to bring a new product to market. Testing of miticides requires experimental use permits and results may narrowly apply to only the test conditions. It is potentially dangerous to colony and derived product quality to test unregistered compounds on your colonies. 2nd NOTE: Master students looking for published research have option to choose their article – articles such as these two would qualify as appropriate.

Sabahi, Qodratollah, Hanan GashoutPaul G. Kelly, and Ernesto Guzman-Novoa. 2017. Continuous release of oregano oil effectively and safely controls Varroa destructor infestations in honey bee colonies in a northern climate. Exp Appl Acarol. 2017; 72(3): 263–275.  doi: 10.1007/s10493-017-0157-3

Photo: Electric vaporizers containing oregano oil installed above the brood chamber of honey bee colonies