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Pesticides, malnutrition blamed for massive bee die-off

A University of California-Davis expert urges bee producers to remove their hives from almond orchards earlier to avoid die-offs like one that occurred at the end of this year's almond blossom.
Tim Hearden

Capital Press

Published on April 15, 2014 7:57PM

Capital Press

DAVIS, Calif. — A top university expert urges beekeepers to start removing their hives from almond orchards earlier to avoid die-offs like a massive one that occurred at the end of almond bloom this year.

Many California beekeepers — particularly in the southern San Joaquin Valley — lost both adult bees and broods after a mixture of fungicides used by almond growers and insecticides applied to field crops proved harmful, said Eric Mussen, a University of California extension apiculturist here.

The deaths of billions of individual bees affected as many as 20 percent of bee producers statewide, said Joe Traynor, whose Bakersfield-based Scientific Ag Co. pairs beekeepers with growers throughout the valley.

Many almond farmers want bees to stick around in orchards until pedal drop to maximize pollination, which in turn boosts yields. But the lack of forage so late in the blossom can cause bees to migrate up to four miles looking for nourishment, Mussen said.

"It's at that time when different pests start showing up in alfalfa hay fields or other orchards or vineyards" and growers start spraying for them, Mussen said. "There's a whole bunch of other places they can get themselves in trouble."

Many losses appeared to occur when a fungicide that normally wouldn't harm bees was blended with an insect growth regulator, Mussen said. Added to the mix were adjuvants — pharmacological agents added to the chemicals to increase their effect — which seemed to get into the bees' food cycle and cause significant problems for bee broods, he said.

"All this new chemistry is staying way far ahead of us," he said.

Perhaps contributing to the deaths of young bees were "starvation conditions" after the almond bloom that may have caused some bees to start cannibalizing their broods, Traynor said.

"It's very confusing as to what the problem actually was," he said.

Some bee producers, including Palo Cedro, Calif.-based Wooten's Golden Queens, removed their bees from orchards early enough that they weren't affected.

"We got out of there before all of this crazy stuff started going on," co-owner Glenda Wooten said.

The latest die-off comes as the mysterious malady known as colony collapse disorder has been decimating one-third of the nation's honeybees virtually every year since 2006, according to UC-Davis. While some environmentalists have been quick to blame pesticides for the die-offs, researchers have cited many other contributing factors, including malnutrition, drought and inclement weather and climate change.

Honeybees are shipped in from around the country to service California's 800,000 acres of almond groves. A warm winter ignited an early and vibrant almond blossom in February, and beekeepers said they had just enough bees to meet this year's contracts and that their colonies were in good health.

The length of time the bees are deployed can be a point of contention between beekeepers and growers, industry insiders said. However, bee producers weren't necessarily in as much of a hurry this year to move on from almonds since there weren't as many other flowers available because of the state's drought.

Mussen said it isn't necessary to keep bees around until the last pedals fall and it could actually leave them scrambling for nourishment. While bees are present, Mussen advises growers to avoid contaminating pollen or collectors with their applications, perhaps by spraying in the afternoon or early evening after the bees had completed their work.


UC-Davis Department of Entomology and Nematology: http://entomology.ucdavis.edu


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