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The strength of a bee colony is important, but it is difficult to assess without looking inside.

The strength of a bee colony is important, but it is difficult to assess without looking inside.

Bees are critical for setting a good crop, though the number of hives needed per acre can vary a great deal. Even a self-­fertile cherry variety needs bees to move the pollen around, Eric Olson, a Yakima, Washington, beekeeper and orchardist, said during an industry discussion.

“Pollination is critical,” he said. “If you don’t have bees in apples, you will have apples, but the quality and the quantity will be greatly reduced. The same with pears and cherries. If you take a look at what it costs you and figure it out on a packed-box basis, it’s the cheapest thing you can do to put a crop on there.”

Olson said he would place ten hives per acre in Bing cherries, but one per acre might be enough for Lapins and Sweetheart. For apples, it depends on the grower’s comfort level and how much of a risk they want to take.

Hermann Thoennissen, orchard manager with HTG International in Kennewick, Washington, said he would rather get extra bees in the orchard than save $20 or $40 and end up with a short crop. Even though he’s afraid of oversetting cherries and ending up with small fruit, they still need to be ­pollinated, he stressed.

Jack Hein, field horticulturist with Olympic Fruit Company in Yakima, said he uses about five and a half hives per acre in apples and three to five in cherries, but it varies by site. He places more bees in sites with cool and windy weather.

Jeff Lunden, a beekeeper and orchardist at Prosser, Washington, and scientific assistant with Washington State University, said that in theory it only takes one pollen grain to fertilize the ovule of a flower, but multiple visits by bees increase the chance of getting good fruit set. One bee visit most likely won’t do the job. However, there’s been no research to show exactly how many hives per acre are needed. “What you’re buying is insurance, especially for the bad years. If you short yourself and get what you need to get by in good weather, and we have bad weather, you’re going to pay for it,” Lunden said.

Bees generally don’t fly in cooler temperatures, but Olson said bee activity depends to some extent on colony strength. “If you’ve got six frames of sick bees out there, at 65°F they won’t be flying,” he said. “But if you’ve got 15 frames of romping, stomping girls in that hive going crazy, they’ll be out at 50°F.”

Hein said that to ensure good pollination, he likes to have two different pollinizer ­varieties to make sure that one or the other is blooming when the main crop is in bloom.

Thoennissen said that usually 10 to 12 percent of his trees are pollinizers, but it depends on the spacing. “I don’t worry about the looks. I just get them in there somewhere where they fit.”

Sometimes he does not plant pollinizers in the outer three or four rows of a block because he figures there will be enough pollination from the neighboring variety.

Hein said he has found that when trees are planted at densities as high as 2,000 per acre, planting a pollinizer every tenth tree wastes a lot of space. For the super spindle ­system, he plants pollinizers every 100 feet on a diamond pattern, and plants both pollinizing varieties in the same hole.

Supplemental pollen

Thoennissen said he has used pollen inserts and bee attractants in pears and thought there was some benefit when the weather was marginal. “When you have 65 to 70°F, you don’t need it,” he said.

If you feel that you need additional pollen, it probably means you didn’t plant enough pollinizers, he observed.

Hein said he has applied pollen by helicopter or a four-wheeler vehicle in blocks that didn’t have adequate pollinizers, but would not apply by air again. He’s seen no benefit from using a bee attractant. “But it makes you sleep better at night,” he said.

Olson said he’s tried inserts and doesn’t think they are worth the money. “If you think about the physiology, you put the pollen on the front of the hive and out come the water gatherers, and where does the pollen go? To the watering hole. Out come the nectar gatherers, and where does the pollen go? To the dandelions or wherever they are getting their nectar. Too many of the bees are going to the wrong places. Pollen is expensive, so you are putting some money into this. You are probably better off getting more hives.”

The panel discussion took place during the Washington State Horticultural ­Association’s annual meeting in December.