Jill Calabro July 14, 2016
Pollinator Health
My 4-year old son loves macaroni and cheese and would happily eat it every day, if I let him. Who can blame him – I would eat butterscotch pie for breakfast if I could. But as adults, we all understand that quality food and the nutrition it provides are crucial to our good health and well-being. Bees are just like us in this regard; they need a quality food source too.
Arguably, in the past we took bee pollinators for granted. That all changed in the 1990s, when reports of honey bee colony declines were first noticed. Beekeepers still report colony declines to this day. Then in 2013, news of a very large and very public bee kill (caused by an off-label pesticide application) spread like wildfire. Increasingly bees have been brought into mainstream discussions, along with questions about what is causing the bee decline. “Saving the bees” has become ingrained in our culture. Unfortunately, a clear and easy explanation (and solution) has yet to emerge, partly because basic information about bee health and needs simply doesn’t exist.
Bees have done their job for centuries: pollinate flowers and produce honey. Beyond the very basics, not much thought was given to the status of bee health or even what is considered normal for a honey bee. Less information is available on native and other bees. Even acceptable levels of annual colony loss are debated. Preliminary data recently released by the Bee Informed Partnership indicate 2015-2016 winter losses around 28 percent and total colony loss around 44 percent. While considered high, these numbers are actually close to a nine-year average.
Natural threats
Given the current state and an influx of much-needed resources, a group of researchers is highly motivated to find some answers.
Honey bees have many pests, both insects and diseases. The varroa mite has emerged as a contender for the No. 1 factor contributing to bee decline. Varroa mites were introduced to Florida in the 1980s and have since quickly spread throughout the U.S. They are parasitic to both adults and brood and transmit deadly viruses that also contribute to bee decline. However, the severity of damage this mite causes nationwide is still poorly defined.
The USDA’s Animal and Plant Health Inspection Service and University of Maryland researchers initiated an effort in 2009 to monitor honey bee pest and disease incidence across the country. In the latest report, populations of varroa mite were greater than expected; 87 to 98 percent of sampled apiaries tested positive for their presence. Furthermore, over 50 percent of apiaries had populations in excess of the established economic threshold just before the onset of winter. Varroa mites are closely linked to virus infections; so, it follows that researchers saw a higher incidence of viral infections (than expected). Four viruses were monitored each year; deformed wing virus consistently had the greatest incidence with levels above 80 percent each year.
A fungal disease, Nosema, was also detected at higher-than-expected levels. Incidence ranged from 42 to 79 percent of sampled apiaries during 2009 to 2014. Adult bees infected with Nosema eventually become too weak to return to the hive and die far away. These pests and diseases likely contribute to the high rates of colony loss reported in the U.S. Researchers also collected pesticide residue data and plan to correlate this with colony health in the future.
What’s the role of insecticides?
In the quest for a simple answer and solution, pesticide use is also being scrutinized. Neonicotinoids, in particular, have come under fire. Reports have varied from showing negligible to severe impact, but the majority of the scientific community agrees that pesticides, neonicotinoids in particular, likely have little impact on colony decline. However, researchers caution that the impact of chronic levels of pesticides in pollen has yet to be determined and may be more injurious to brood. Federal, state and local officials have reacted to the conflicting information and fear with the introduction of new regulations meant to reduce bee exposure to pesticides. The EPA has undertaken an in-depth analysis of the impact of neonicotinoids to honey bees and has plans to evaluate other pesticides in the near future.
Dr. Nancy Ostiguy, Associate Professor of Entomology at Penn State University, led a nationwide study evaluating pesticide exposure to honey bees over a four-year period. While insecticides were most commonly detected in pollen samples, the most frequently detected pesticide was the herbicide atrazine. The second most frequently detected pesticide was the fungicide carbendazim (not registered for use on ornamentals) followed by the insecticide carbaryl. Of fungicides detected, the most common were carbendazim, azoxystrobin and propiconazole. Of the herbicides, the most commonly detected were atrazine, pendimethalin, and metolachlor. The most commonly detected insecticides included carbaryl, malathion and chlorpyrifos, not neonicotinoids.
Why are pollen and nectar so important?
Simply put, pollen and nectar are bees’ food source. Pollen is the source of protein and fats/lipids essential for brood and young bee development, while nectar is a source of carbohydrates, or sugars, primarily for adult bees. As it turns out, the quality of pollen and nectar (in terms of bee nutrition) varies greatly from plant to plant and even among varieties. For example, Buddleia is wildly attractive to pollinators but is akin to junk food in terms of nutrition.
A study conducted by French researchers found that the quality of pollen, specifically protein content, directly impacts bee health. Honey bee survival of Nosema infections significantly increased with a diet of protein-rich pollen, as compared pollen with low protein content. They concluded that, similar to humans, pest and disease resistance increased with a higher quality, nutritious diet. They compared protein content of four plant species and found that Rubus (raspberry, blackberry) had the highest protein and, therefore, the highest quality pollen. Cistus (rockrose) had the lowest.
Supplemental pollen pellets and sugar syrup are often fed to colonies during periods of low foraging or plant availability. Attempts to make synthetic pollen and nectar for honey bees have failed. Dr. Ostiguy commented, “We have not successfully created a pollen substitute. When honey bees are given an option of synthetic pollen or natural pollen, they always choose the natural pollen. It’s a similar situation with nectar, and we don’t know what is missing.”
That begs the question, what is the nutritional quality of common landscape plants?
Right plants, right places for pollinators
Prevailing wisdom would indicate that native plants are more nutritious for bees, especially native bees, since they evolved together. But this is not always the case. Sometimes nonnative varieties or introduced species are a better pollen and nectar source than the wild type. For example, bees prefer certain, cultivated varieties of salvia to wild types.
Several researchers worldwide are focused on surveying which landscape plants are most frequently visited by bees. A few, key folks have honed in on plants common to U.S. greenhouse and nursery production. This is important work for a number of reasons, including pollinator habitat restoration and pest management techniques – knowing when to use what pesticide (or not use), if needed.
Dr. Dan Potter, University of Kentucky, initiated his second year of surveying woody plants, both native and nonnative, for pollinator attractiveness. A key component of the project is documentation of which bees prefer which plants, called bee assemblages. Potter has, so far, surveyed more than 60 different woody plants and found that different plants attract different, unique bee assemblages. For example, crabapple flowers attract a wide variety and diversity of bees while linden attracts fewer, more specialized bees.
Another group at Penn State University, working with Pollinator Partnership (http://www.pollinator.org), is conducting similar surveys on both annual and perennial herbaceous plants that are important to the green industry. This group is considering the context of plants in the landscape and looking at a suite of pollinators that are attracted to the plants. They are also analyzing the nutritional quality of the plants for pollinators in a related project in collaboration with other universities.
Dr. Harland Patch, a research scientist and lecturer at Penn State, who is involved with this project, comments that “Places with the highest demand for pollinators tend to have the lowest quality landscape for them. We should improve the landscapes where we live and work for the bees. I don’t think it’s very hard. We are coming close to having some good answers and recommendations people can use.”
Both of the above research groups envision a plant labeling system that includes information about what bees are attracted to it, as consumers are eagerly supporting efforts to “save the bees.” Various industries are already benefiting from bee-related marketing, from ice cream to cereal manufacturers. The green industry is poised to be a leader in this campaign.
So while I do give in and let my son have macaroni and cheese from time to time, I am mindful to make sure he has a good source of protein and other nutrients in his diet as well. As an industry, we can be mindful of bee health through safe production practices and promotion of pollinator attractive and nutritious plants. As pollinator surveys progress and techniques for evaluating pollen and nectar improve, look for more information in the near future. Horticultural Research Institute has dedicated over $160,000 of funding and leveraged an additional $300,000 toward research contributing to pollinator health, including some of the aforementioned studies.