There are ample reasons to remove honeybees from an almond orchard after they have done their pollination job, including not leaving them there to decrease the risk from harm by pesticide use.
Kern County, Calif. bee broker Joe Traynor, in an Internet posting, speculates there could be another reason to not leave them in the orchard too long. They are “nectar hogs” that can deplete a tree’s resources as they continue to collect nectar well after pollination is over.
Traynor concedes an observation echoed by University of California researchers. His provocative speculation is theory: “I like to throw things out there to make people think. There’s no basis of proof; I would like to see it tested.”
So would Ted DeJong, professor and pomologist with the University of California, Davis Department of Plant Sciences.
“It’s an interesting theory, but it’s likely not that simple,” DeJong said, referring to the article by Traynor, a consultant and manager of Scientific Ag Co. in Bakersfield.
DeJong points out the same warmer temperatures at which bees thrive is also at levels where trees show a higher growth rate, which demands more carbohydrates.
“If the carbohydrate demands for all fruit are greater than the trees can supply, then some fruit abort and those fruit drop,” he said.
Traynor said it’s possible that when a bee visits a tree often, it takes away energy the tree needs for nut development. He said bees this year weighed as much as 10-15 pounds per colony more when they were removed compared to when they entered an orchard.
Traynor said this year’s temperatures in the 70’s were ideal for nectar secretion.
“The bloom was compressed into a shorter window, but it was a good year for pollination,” he said.
Traynor said pollen is a rich source of nutrients and protein, and is the primary food for pollinating insects.
“Nectar is the fuel that propels the insect from flower to flower – the gasoline that carries the insect to the grocery (pollen) store,” he said.
Honeybees have been bred, he said, to store nectar “far in excess of their immediate needs.”
As bees forage in the orchard after pollination has been completed, he said they turn almond trees into nectar producing machines that cause trees to “bleed” carbohydrates.
UC Professor Emeritus Robbin Thorp of the Department of Entomology confirmed the trees continue secreting nectar after all the petals have gone.
“The bees will continue to visit,” Thorp said. “It blew my mind when I first saw it.”
Traynor’s speculation - “Weather during almond bloom can be ‘too good.’ A warm spell right after pollination could cause excess nectar flow and nectar collection by honeybees. This could partially explain why disappointing almond crops sometimes occur after ideal weather throughout the blooming period.”
He cited studies conducted in 1977 by U.S. Department of Agriculture researcher Phillip Torchio to evaluate a wild bee species as a pollinator for almonds. Trees caged with the wild
bees out-yielded open pollinated trees.
The wild bees collect relatively little nectar from flowers, Traynor said, “only enough to fuel their flights to flowers and serve as ‘glue’ for their pollen loads. . . Compared to wild bees, the honeybee is a nectar hog.”
DeJong said the research comparing the wild bee and honeybee “sounds like that was not a large replicated trial. It would be worthwhile to do that experiment with adequate replication and controls.”
Meanwhile, The Wonderful Company, formerly Paramount Farms, continues to look at adding the blue orchard bee, a native, to the pollination mix. That’s the same bee studied by Torchio.
Gordon Wardell, director of pollination operations with The Wonderful Co., said the company is not looking to replace honeybee colonies, but to use the wild bee in tandem with honeybees.
DeJong said a researcher with the University of California is also looking at alternative types of bees for pollination.
“Another thing that should considered is that in walnuts, which are wind-pollinated, there is now good evidence that some cultivars, especially Serr, can be over-pollinated and excess pollen causes early fruit drop or pistillate flower abortion,” DeJong said.
In a March press release, the Almond Board of California stated, “With almond bloom winding down, it is vital growers track petal fall and crop development in their orchards so that bee hives are released to beekeepers and removed from the orchard at the optimum time.”
The board said it has a best management practices publication which includes tips on the timely removal of honeybees from the orchard after pollination. It says bees should be removed when 90 percent of the latest blooming variety is at petal fall.
“Bees not removed at this time may travel outside of orchards in search of alternative food sources,” the publication says, risking their coming into contact with other insecticide-treated crops.
As a pollination season comes to a close, growers and beekeepers are urged to monitor hives for suspected pesticide-related incidents.