Nature meets honeybees’ seasonal nutritional needs naturally. The information could be used to tailor flower mixes for pollinator habitat to support bee health.
A study by USDA Agricultural Research Service (ARS) scientists tested a hypothesis that nutrients in seasonal pollen was meeting bees’ seasonal nutritional needs just as seasonal plants support seasonal nutrition for many wildlife species.
“We thought there might be a similar relationship between honeybee nutritional needs and nutrients in seasonal pollens,” said ARS entomologist Gloria DeGrandi-Hoffman, research leader of the ARS Carl Hayden Bee Research Center in Tucson, Arizona. “In the spring and summer, honeybee colonies concentrate on raising new bees. In the fall, they shift to preparing for a winter that is often spent in the hive surviving the cold. These activities may have different nutritional needs.”
Determining how pollen from different seasonal flowers meet bees’ nutritional needs is key to maintaining bee colonies’ health, according to DeGrandi-Hoffman. That information could be used to customize seed mixes for pollinator habitat by season and location.
The study compared differences among spring and fall pollen collected by bees in central Iowa and southern Arizona. Although the bees foraged different types of flowers in the two states, the spring pollens contained similar nutrients, especially the essential amino acids and many fatty acids needed to rear new bees.
In the fall, Iowa honeybees gather pollen from asters and other flowers whose pollen has higher levels of some nutrients that may better support bee colonies through a cold winter.
Interestingly, the Iowa spring pollen had higher levels of the essential fatty acid, omega-3, compared to that in Arizona. The researchers found higher levels of omega-3 were associated with honeybees having larger hypopharyngeal glands, or HPG. HPG produce a jelly that is fed to the queen and young developing bees. Larger HPG make more jelly, which allows more worker bees to be raised.
“This suggests clover species, which largely made up the spring Iowa pollen, could be an important nutrient source for colony growth since it provides high levels of omega-3,” DeGrandi-Hoffman said. “Therefore, clover should be included in pollinator plantings.”
Fall flowers species and pollen nutrients also differed between the two states. Iowa fall pollen had higher levels of certain amino acids and lipids (fats).
“Higher concentrations of these amino acids and lipids in fall Iowa pollen may better support honeybee colonies confined during the winter,” said DeGrandi-Hoffman. “Honeybees are not confined for long periods during southern Arizona winters and may not require the same level of fat stores.”
In Iowa, the fall pollen primarily came from flowers in the aster family with small amounts from allium, partridge pea, ragweed and goldenrod species. The spring Iowa pollen mostly came from clover species along with honeywort and plains mustards.