The study encompassed observations in 17 cherry orchards in eastern Germany, where some growers utilized honey bees in hives as pollinators, while others relied on wild mason bees.
To maximize cherry harvests, a combination of honey bees and mason bees should be employed for pollination, according to a recent study led by a researcher at the University of Gothenburg. This research underscores yet another advantage of biodiversity in agricultural practices.
Most sweet cherry cultivars, like many other fruit trees, rely on cross-pollination to yield fruit. This necessitates the presence of several different cultivars of sweet cherry trees in an orchard to facilitate the transfer of pollen by bees.
Julia Osterman, a biologist at the University of Gothenburg and lead author of the study, explains, “Sweet cherry trees are usually planted in alternate rows of different cultivars and in some cases, you can put different cultivars in the same row, but this can make harvest logistics tricky. In other words, the bees have to fly from one row of trees to the next to ensure that the trees set fruit.”
Collaborating with German researchers from Martin Luther University Halle-Wittenberg, Osterman discovered that when trees were pollinated by multiple bee species, they yielded a larger quantity of cherries.
The study encompassed observations in 17 cherry orchards in eastern Germany, where some growers utilized honey bees in hives as pollinators, while others relied on wild mason bees. Certain orchards implemented both species to varying degrees, and those with a combination of both showed a notable increase in fruit set.
“The orchards with honey bees and lots of mason bees could have cherries on up to 70 per cent of the blossom. In orchards with only honey bees or only mason bees as pollinators, the rate could be as low as 20 per cent,” notes Osterman.
Many growers were already utilizing two bee species, often as a contingency if the weather was too cold for honey bees during cherry tree blossoming, as cherries bloom early. While honey bees require temperatures above 12°C to become active, mason bees can function in cooler conditions. The significant uptick in fruiting occurred when both species were active, and researchers are now exploring the underlying reasons.
“One theory is that the presence of mason bees affects the foraging behavior of honey bees,” suggests Osterman. “This disturbs them and so they change rows more often, resulting in more cross-pollination. But all we know at the moment is that interaction between the bees produces a synergy effect.”
This research holds practical implications for cherry growers, who can encourage wild mason bees by providing suitable nest materials. Mason bees, being solitary, focus on collecting pollen for their offspring and nest in tube-shaped spaces.
Fruit growers can attract mason bees to their orchards by placing bamboo or wood with drilled holes. However, there seems to be a limit to how many mason bees can be attracted, regardless of the amount of nest material provided.
Similar findings have been observed in almond orchards, prompting Osterman to explore whether this synergy effect extends to other fruit trees and delve into the precise dynamics between the two bee species.