MSU pollination project expands to investigate an alternative pollinator

An alterative pollinator, Osmia cornifrons, will be evaluated for its pollination potential in Michigan cherry orchards.

In northern Michigan, spring still seems like a ways off, but the MSU Integrated Crop Pollination team is preparing for bloom in cherry. This season, we will be expanding our project to include the use of the alternative pollination, Osmia cornifrons, horn-faced bee, in tart cherry orchards. This bee is a pollinating species native to Japan and is similar in behavior to that of other closely related species such as the blue orchard bee or mason bee. The blue orchard bee has been used extensively in orchards in the western United States due to their exceptional pollination traits. They are extremely efficient pollinators and they prefer to forage on fruit tree flowers. O. cornifrons also flies under cool and cloudy weather, which makes them a desirable pollinator in cooler spring conditions. Because fruit growers can mimic Osmia nesting sites and because these insects are excellent pollinators, we are interested in investigating their use in Michigan orchards.

These bees have many different attributes from our traditional honeybees. O. cornifrons nesting habits are not social – they do not have queens and workers. Instead, each female bee is fertile and lays her own eggs and provisions her own nests. Males do not help with nest provisioning, but they do visit flowers for nectar; therefore, they do contribute to pollination in this way. Females collect pollen for themselves and for their brood, so they are able to pollinate many flowers. O. cornifrons carry dry pollen on a scopa, a brush of long hairs on the abdomen, rather than pasting the pollen to their hind legs like honey bees.

HFB in tubeOsmia cornifrons become active in early spring, close to the time of cherry bloom. Males emerge first, followed by the females one to three days later. Once a female is mated, she feeds for one to two days and then she begins the nest building process. She chooses nest sites with her preferred dimensions, a tube 5/16-inch diameter and 6 inches in length. She ultimately divides the tube into five cavities that are separated by a mud partition. In each cavity, she lays an egg. She also creates a nectar or pollen packet inside each cavity for the larva once it hatches. The most inner two cavities of the tube usually contain two females and the outer three cavities house male offspring; the entire tube is sealed off with a thicker mud partition. In the spring, the adult bees must chew through the mud wall to emerge.

Osmia cornifrons takes several months to complete its lifecycle, and they only produce one generation per year. After the adult bees emerge in spring, they mate and females lay eggs in nesting tubes. In about one week, the eggs hatch, but the first instar remains in the egg and feeds on the egg’s fluids. Three larval stages follow, and these stages of the bee feed on the healthy provision left by their mother. At the fifth instar stage, the larva spins a silk cocoon where it remains in this “prepupa” stage during a summer dormant period. By late summer, the prepupa molts, then molts again into the adult stage after one month. Adult bees remain in the cavity throughout the winter; this species needs an obligatory cold period during overwintering to successfully emerge in the spring.

The MSU team will evaluate O. cornifrons and their potential for pollination in tart cherry orchards in northwest and west central Michigan. The literature has shown that horn-faced bees have a preference for fruit tree flowers and that females collect both nectar and pollen concurrently. This behavior forces the bee to literally dive inside the corolla to find the nectar while they attempt to gather pollen on their rudimentary scopa. The result is complete contact between stigmas and anthers for the bulk of flower visits. These bees also move readily from tree-to-tree and row-to-row, and this foraging technique facilitates cross-pollination. These bees are also more apt to fly under cloudy skies and at cooler temperatures more readily than honey bees. Evaluation will begin at bloom this spring.

Dr. Rothwell’s work is funded in part by MSU’s AgBioResearch.

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