This spring has been cool and wet, and I am sure I don’t need to remind area citizens of this weather pattern. We are all hoping spring will arrive soon!
Fruit growers and their pollination helpers — honeybees — also are eagerly awaiting warm and sunny conditions. With the cool temperatures, tree development has been very slow. We have had various amounts of open bloom in sweet cherries for the last few weeks. Tart cherry bloom is just finishing in the southern growing areas and are opening further north.
Apples are in full bloom at the Northwest Michigan Horticultural Research Center this week (May 30, 2019). We have had lots of questions about the success of pollination, both with the cool temperatures limiting honeybee flight and the likely slow pollen tube growth that would result in successful fertilization.
This spring’s cool and wet conditions have impacted honeybee activity.
We know rain and cold weather impact bees and keep them in the hive. The warmer the temperatures, the better conditions for bee activity.
Honeybee flight muscles need to reach 68 degrees for them to fly. But bees can keep temperatures warmer within the hive than the ambient outside temperatures. Additionally, bees are able to warm their muscles and can fly in temperatures as low 50 degrees.
However, sun will impact honeybee activity, so if the air temperature is around 50 degrees with sun hitting the hive, the bee activity will be higher than 50 degrees with wind and rain.
Honeybees will also fly in light, misty rain but not in heavy showers. Many times, bees can get caught in heavy rains and will wait out the rain and dry off before returning to the hive.
Honeybees will forage for up to three miles, and they prefer to forage in crops with high reward, such as ample nectar and pollen resources. Most pollination will occur in the first mile from the hive, but they can forage to further distances if there is a shortage of food.
This year also seems to have a bumper crop of dandelions, perhaps also because of the cooler conditions. Growers have questioned if these dandelions provide benefit to the hive or if they compete with cherry/apple bloom. Researchers have found that the colony as a whole does better with various species of pollen.
Colony hive strength is key to successful pollination, and a stressed or weak honeybee colony will stay in the hive and concentrate on brood rearing rather than foraging; healthy hives will work outside the hive more actively and will provide more pollination services.
Cherry blossoms (and other fruit flowers) are very rewarding, and honeybees will readily choose cherries over dandelions.
Hence, dandelions will likely contribute to the health of the hive rather than directly compete with cherry blooms.
Lastly, with these cold temperatures, beekeepers have been feeding bees with sugar water (high fructose corn syrup or sucrose water).
This supplemental feeding is necessary when temperatures are in the 30s and 40s because the bees do not leave the hive to forage but still need food. This sugar water provides resources for bees if no natural food is available (or if temperatures are too cold for bees to fly to forage). This sugar water supplement does not impact bee foraging or pollination services, but helps maintain a healthy hive.
All of the region’s residents, including honeybees, hope for warmer and drier weather in the coming weeks.
But Michigan State University Climatologist Jeff Andresen predicts more cool and wet weather in the short-term.
The few warm and sunny days we have had thus far this spring were enough to get our honeybees out of the hive and flying. At this early point in the season, we can expect good cherry and apple crops, and we are hopeful for a prosperous season ahead.
Nikki Rothwell is a Michigan State University Extension district horticulturalist and coordinator of the Northwest Michigan Horticultural Research Station.