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Computer simulation software designed for almond set prediction

Computer simulation software to give California almond growers an idea of what their crop will be is being refined by scientists at USDA-ARS's Carl Hayden Bee Research Center at Tucson, Ariz.

Leader of the center and honey bee expert, Gloria DeGrandi-Hoffman, explained the program during presentations of the Almond Board of California (ABC) conference at Modesto, Calif.

The simulation model, known as “ALMOPOL” and designed as a Web site for growers, predicts cross-pollination in an almond crop. Activated when almond bloom appears, it takes into account the amount of bloom of the varieties of an orchard, the number of bees per acre, and weather data to generate an estimate of the set.

DeGrandi-Hoffman noted that the role of honey bees in successful almond pollination is essential but not the sole deciding factor. For example, temperatures below 70 degrees F, and the presence of wind and cloud cover discourage them from leaving the colony and limit the amount of foraging they can accomplish.

She said cross-pollination depends on the amount of pollen from respective varieties brought into colonies. The bees move between trees to distribute pollen, and it is also spread between bees once they return to their colony. Thus, the more pollen from one variety brought into the colony, the more nuts of that variety can be set.

“The best cross-pollination occurs when there is substantial bloom overlap. So orchard design ultimately seals the fate in terms of how much cross-pollination can go on in different weather conditions,” she said.

“In situations where there isn't good bloom overlap, all the bees in the world can't make a difference. Cross-pollination also depends on high-quality flowers, and more of it takes place prior to peak bloom or immediately afterward.”

Now that the basic program has been designed, she said it needs more field data and validation from growers, who are being encouraged to try it and make suggestions for improvements.

It can provide, DeGrandi-Hoffman said, a platform to generate additional production information, such as return on investment in bee colonies.

Another speaker at the conference, Susan Cobey, bee geneticist at the Harry Laidlaw Honey Bee Research facility at the University of California, Davis, discussed the Honey Bee Stock Improvement Program, which enhances the genetic diversity of the insects.

Stronger diversity and the potential resistance to pests and diseases it provides, she said, will be the long-term solution to the decimation of bees during the past 20 years by tracheal mite, Varroa mite, and, more recently, colony collapse disorder, which alone claimed 30 percent of the bee colonies in the U.S. in 2006.

Importation of new honey bee species into the U.S. was banned in 1922, and since that time the main two subspecies here have been Italian and Carniolan.

However, with approval of USDA's Animal Plant Health Inspection Service, Cobey's program is importing semen of three subspecies during 2008-2010: one from Italy, one from Germany, and one from Turkey. Each subspecies is thought to possess valuable disease and pest resistance that can be introduced to strengthen domestic honey bees.

After supplies are screened for viruses and have completed required quarantine procedures, they will be distributed to interested California queen bee producers, Cobey said.

Eric Mussen, cooperative Extension apiculturist at UC Davis, urged beekeepers producing queens to keep colonies away from any pesticides, not only fungicides, and recommended growers spray only when bees are least active in the field.

He said since the 1950s beekeepers have blamed Captan fungicide for brood losses. Rovral later was documented to cause some losses, and more recently some complaints about Pristine have emerged, although losses have not been documented.

Generally, the problem is larvae, pupae, and emerging adults disrupted by something that ruined their chemical balance. The brood loss effects are not immediate but visible about 17 days after exposure.

One symptom beekeepers often detect in affected colonies is improper wing development in adults, which is also a sign of buckeye poisoning or Varroa mites. Often buckeye problems occur first when foraging bees pick it up, but it can break out again later when they use supplies of stored pollen.

“Fungicide problems, although they are observable in the lab, are probably not as important as buckeye poisoning,” Mussen said.

“Fungicide exposure is probably only one day if applied by air, and two or three days when applied by ground rig but buckeye trees can be in bloom for two or three weeks.”

Although bees in a typical colony can compensate for some population loss, he explained, in a queen-rearing operation, beekeepers must have healthy larvae for normal production.

Growers can ease bee losses by applying potentially harmful pesticides when the bees are not flying. “In almonds, this is pretty straightforward, since there is no pollen in the field until it is 55 degrees F or warmer,” he said.

“So if it can be done within the often small window that growers have, putting on sprays late in the afternoon and into the evening is significantly less apt to contaminate foraging bees,” Mussen added.

Chris Heintz, liaison for the ABC Bee Task Force, said research to improve honey bees extends across the nation, one leading example being Florida's effort with $300,000 in the past four years.

The Bee Task Force was formed in 2005 by the ABC, which has often allocated about 20 percent of its production research funds to bee pollination research projects.

The task force is composed of growers, beekeepers, and researchers who screen proposals for the board. Its 2008-2009 funding is $156,000 for projects such as stock improvement, Varroa mites, diseases, and blue orchard bees (considered a supplemental pollination resource, but not a replacement, to honey bees).

Heintz is also director of Project Apis m., or Pam, named after the species name for the European honey bee, Apis mellifera. Formed at the ABC conference in 2006 by honey processors, beekeepers, and orchardists, it is dedicated to funding practical research on managed honey bee colonies.

Among its current projects, she said, is development of diagnostic services for virus detection for specialty laboratories serving the honey bee industry and pesticide screening.

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