The objective of this study is to compare the effects of various artificial carbohydrate sources on honey bee health, overwintering survival, and spring population build-up. Honey bee worker digestive health and pesticide resilience will also be determined.
Hypothesis 1: Honey bee colonies fed honey and invert syrup (ProSweet) will have higher overwintering survival than those fed sucrose syrup or high fructose corn syrup.
honey = prosweet > sucrose = hfcs
Hypothesis 2: Consumption rate of the four winter foods will be equal. honey = prosweet = sucrose = hfcs
Hypothesis 3: Honey bee colonies fed high fructose corn syrup will have the smallest brood area of the four treatments. Honey and invert syrup (ProSweet) will have the largest brood area, followed by sucrose syrup.
honey = prosweet > sucrose > hfcs
Hypothesis 4: The honey bee gut microbiome will be changed by all three artificial feeds as compared to honey. honey does not = sucrose or hfcs or prosweet
Hypothesis 5: The resilience of worker bees to a pesticide challenge will be greatest in those fed honey for honey and less for those fed all three artificial feeds.
honey > sucrose or hfcs or prosweet
Sucrose and high fructose corn syrups (hfcs) have been studied for their effects on honey bees. Research shows that sucrose syrup and high fructose corn syrup are equally accepted by and utilized by honey bees (Severson and Erickson 1984). However, after wintering with the sucrose and hfcs feeds, those with sucrose had higher brood areas in spring (Severson and Erickson 1984), which could lead to larger populations, higher income from pollination contracts, and higher honey production. Lab studies have shown that the lifespan of worker bees is longer when fed exclusively sucrose syrup than when they were fed either honey or hfcs (Barker and Lehner 1978). Studies of the sugar content of royal jelly, the first food of bee larvae and the only food of queen honey bees, showed no impact from various carbohydrate feeds (Sesta et al. 2006). A comparison of sucrose syrup, invert syrup, and starch syrup showed no difference in overwintering mortality in Austria (Brodschneider et al. 2010). In a 2011 SARE-funded project (FS11-252), Barry Harris and David Tarpy studied various winter feeds in North Carolina. In their warm climate, they had excellent survival on all feeds tested, including all of the feeds we plan to use in this study. They also tested the bees for Nosema disease and found no difference between treatments. Most of these studies, however, did not compare the feeds to honey, bees’ natural food, but to each other.
In addition to differences in sugar composition between the feeds (Table 1) there are also other differences. Honey contains pollen, minerals and other ingredients that would be entirely missing from artificial carbohydrate sources. In fact, Mao and colleagues (Mao et al. 2013) determined that there are components of honey that affect the immune system of bees by upregulating detoxification genes. Thus, honey aids in protecting bees because it contains p-coumeric acid, which is missing from other feeds such as sucrose syrup and high fructose corn syrup (Johnson et al. 2012, Mao et al. 2013). This may leave the bees that feed on artificial carbohydrate sources more vulnerable to pesticides and infections. Thus, providing a nutritional diet may be the key to resilience to stress(Doublet et al. 2015, Dolezal and Toth 2018). We will conduct a laboratory assay to determine whether spring-reared bees have differences in their susceptibility to the agricultural pesticide chlorpyrifos.
The honey bee gut microbiome contains a core set of bacteria, which have been shown to be capable of digesting and metabolizing plant-based carbohydrates (Zheng et al. 2017). This microbiome affects the pH of the gut and impacts bee growth, behavior, hormones and physiology (Zheng et al. 2017). Changes to the core microbiome have been shown to have a negative impact on bees, making them more susceptible to diseases (Hamdi et al. 2011) and impacting expression of vital developmental genes, including vitellogenin (Maes et al. 2016).
The honey bee gut contains microorganisms that aid in digestion (Lee et al. 2015). If the composition of microorganisms, termed the microbiome, is disrupted, it can have a major impact on health. We are interested in understanding whether the type of carbohydrates fed to the bees changes the composition of the microbiome in any way. Thus, a subset of colonies will have bees lab-tested for effects of these feeds on the microbiome of the bees that are reared during feeding.
In August 2019, 48 honey bee hives were fitted with broodminder scales and temperature monitoring devices. These allow for continuous monitoring of ambient and in-hive temperature and overall hive weight. Data is being collected to determine the rate of colony weight loss over the winter.
The hives were numbered randomly assigned to one of four feeding treatments: honey, prosweet (invert syrup), high fructose corn syrup, or sucrose syrup (2:1). Honey supers were removed, extracted and replaced to give the bees room to store the feed. Feed was added, up to 5 gallons per hive.
Each month, the hives are visited to ensure that the colonies are alive and that all is well. If a colony has died, its entrances are closed to prevent bees from other treatments from robbing the hives for feed that is different from the one they were assigned.
This research has only just begun. The bees have been fed according to their assigned treatments. Now they are overwintering on that feed.
So far, 9 of the 48 colonies have died. Most of these are at a single site, which looks like it is not a good location for overwintering honey bees.
Nothing yet to report.
Education & Outreach Activities and Participation Summary
These activities will occur at the end of the project, when we have results.
Nothing yet to report
nothing yet to report
Nothing yet to report