Damp April hinders fruit pollination, OSU professor, beekeeper say
By JOHN SCHMITZ
For the Capital Press
Chilly, damp spring weather interfered with many fruit pollinations in the Willamette Valley as honeybees chose the comfort of their hives over foraging for pollen and nectar.
Not helping matters were periods of frost during strawberry bloom.
"We probably had about 25 days of rain in April," said Oregon State University Extension berry crops professor Bernadine Strik on May 5. "Honeybees do not like to fly in cool, rainy weather."
As to the effect on fruit set, it's too early to tell, Strik said. "(With blueberries) it requires several visits by honeybees to the same flower to get a high number of seeds per berry."
The seed number is related to size, she said.
"Low fruit set can be reflected in fewer berries and smaller size. That's something growers will be looking at," Strik said.
"The good news is that fruit bud set was exceptional this past fall," Strik said. "Most blueberry fields are loaded with flowers."
She said the warm weather in early May is welcome.
"On May 7, it finally got to 60 degrees Fahrenheit, and I've never seen so many bees in a blueberry field," she said.
Strik said bumblebee activity was higher than normal this year.
"They'll fly no matter what. But for the impact of that, we'll have to wait and see," she said.
Historically, bad weather during strawberry bloom can limit bee activity, which in turn can affect berry shape.
"We'll be able to tell in the next couple of weeks just what impact this has had," Strik said.
Willamette Valley cherry pollinations were late this year, said Salem beekeeper Harry Vanderpool, who rents his bees to several Salem-area orchardists.
"What happened was that we were about 50 heat units ahead -- all that warm weather in March -- and then you know what happened," he said, referring to the cool, wet April.
Entomologist Rufus La Lone said that any reduced fruit set due to poor bee activity, especially in fresh market cherries, may be a blessing in disguise, owing to the bumper crop last year that depressed prices.
Vanderpool, who placed his bees in cherry orchards April 8, said that, overall, pollinations of briner and fresh market fruit in the Willamette Valley were "really patchy."
"What we've seen this year is that some varieties, particularly early varieties such as Corums, were impacted," he said. However, some of the later fresh market varieties were pollinated "pretty darn good."
Vanderpool said that orchard elevation also played a role, with lower, warmer elevations promoting more honeybees foraging.
Vanderpool said one of his cherry-growing customers told him that if all three conditions -- bees, sun and bloom -- are ideal for pollination, bees need only three hours to achieve a good pollination set.
"That's the advantage of honeybees over all other pollinators, that brute force," he said.
Vanderpool said his bees do a better job in cherry orchards when they're placed on top of large, upside-down cherry totes, one pallet of bees per tote.
"That gets them off the cool ground and flying a little earlier in the morning," he said.
Vanderpool, who also rents bees to valley meadowfoam growers, said that pollinations are about a week late due to weather.