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Protecting Pollinator Health

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ARS promotes sustainable crop production by protecting crops and pollinators from pests that threaten their health and consequently reduce crop yields. More than 4,500 invasive pests damage crops, costing U.S. agriculture an estimated $30 billion annually. In addition, the risks posed to bees by invasive mites, beetles, and disease is equivalent to $15 billion in lost pollination services for fruit, nut (almond), and legume crops. The following FY 2020 accomplishments highlight several ARS advances in pollinator health and pest management research.

Spirulina as a promising nutritional supplement for honey bees. Feeding honey bees an artificial pollen substitute diet to support colony health during periods of reduced forage is a common management practice by beekeepers, but most substitute diets need improvement. Artificial diets may be deficient in essential macronutrients (proteins, lipids, prebiotic fibers), micronutrients (vitamins, minerals), and antioxidants. In an effort to improve artificial diets, ARS researchers in Baton Rouge, LA, evaluated the nutritional aspects of the microalga Arthrospira platensis (commonly called spirulina), finding that spirulina is rich in the essential amino acids and functional lipids commonly found in pollen. Nutritional physiology and microbiome evaluations of bees fed spirulina closely matched those of bees fed a natural pollen diet. The study results thus show that the alga has significant potential to serve as a pollen substitute or prebiotic diet additive to improve honey bee health. Results of the study were highlighted in the August 2020 edition of American Bee Journal. More broadly, adapting beekeeping and broader livestock management practices with microalgae feeds could contribute to achieving objectives outlined in the United Nations sustainable development goals related to food security, sustainable water management, reversal of land degradation, and halting biodiversity loss. The long-term aim of this research is to characterize and develop microalgae as a sustainable feed source for honey bees that can be augmented via biotechnology to improve bee nutrition and health.

Access to U.S. Conservation Reserve Program (CRP) lands greatly improves honey bee colony health. The honey bee nutritional landscape is critical to the sustainability of commercial beekeeping and modern agriculture, but such landscapes are diminishing rapidly. ARS researchers in Tucson, AZ, exposed colonies to either USDA CRP lands or intensively cultivated landscapes and found that colony survival and future pollination potential were significantly improved by habitat conservation efforts. Colonies exposed to CRP landscapes showed markedly improved size, performance, and function. Mirroring these increases, functions that increase disease resistance were significantly greater in colonies exposed to CRP landscapes compared with those that were exposed to intensive agriculture. The study validates the overwhelming utility of U.S. conservation lands in pollinator health.

Centipedegrass lawns support numerous bee species. In the United States, turfgrasses are a major component of the landscape and cover more than 40 million acres. Centipedegrass is a warm-season turfgrass that is often grown in the southeastern United States. Recently, honeybees were documented collecting pollen from the flower structures of centipedegrass. To understand the role of turf species such as centipedegrass in supporting pollinators, ARS researchers in Tifton, GA, and scientists from the University of Georgia surveyed bees in centipedegrass lawns in central and southern Georgia. Numerous bees were observed, of which 79 percent were Lasioglossum species (sweat bees). Minor species observed included long-horned bees; other species of sweat bees, including metallic green sweat bees; bumble bees; leafcutter bees; and small carpenter bees. These data indicate that diverse bees are residing in or near lawns and forage in and around the lawns seeking centipedegrass flowers. The knowledge that many bees are present in centipedegrass lawns indicates that homeowners and landscape managers should apply insecticides conservatively, since certain insecticides are toxic to foraging bees in lawns.

Impact of climate change on alpine bee communities. Bees in alpine environments face many challenges, including harsh weather and finding floral hosts. Climate change can disrupt plant-pollinator systems through a temporal mismatch, if bees and flowering plants differ in their phenological responses to warming temperatures. While the cues that trigger flowering are well understood, little is known about what determines bee phenology. A 9-year study in the Colorado Rocky Mountains by ARS scientist in Logan, UT, found that bee emergence was sensitive to snowmelt timing, but that bee phenology was less sensitive than flower phenology to climatic variation, potentially reducing the synchrony of flowers and pollinators. However, large-scale outbreaks of bark beetles result in more dead trees but also greater diversity and number of flowers in the open canopy, which resulted in greater alpine bee diversity and numbers, suggesting that outbreaks may aid in conservation of pollinators in forests.