SCANDIA, Alta. — Experiments to control chalkbrood, a fungal disease that kills bee larvae, are being conducted by the Alberta Alfalfa Seed Commission this year.
Alfalfa seed growers depend on healthy leafcutter bees to pollinate their crops and many of them manage their own bees.
Chalkbrood fungus, first discovered in Alberta in the mid-1980s, spreads by spores that infest the guts of bee larvae, eventually consuming them and leaving only a chalky substance behind.
Weldon Hobbs, a commission director, said prevalence of chalkbrood infestation in Alberta leafcutter bees ranges from zero to 16.5 percent, but average infestation is about 1.5 percent.
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That doesn’t sound like much until one considers that a single infected larva can produce up to 250,000 spores and it only takes about 50 spores to kill a developing bee.
“The dynamics of the infection rate would almost indicate that you wouldn’t need it very much in any one place before populations are totally decimated, and that’s exactly what happened in the United States starting in the mid ’70s all the way to the early ’80s.”
Chalkbrood can spread on bee nesting material and equipment that carries the spores.
Hobbs said the commission is testing two control methods, a probiotic applied via misting and a lysozyme applied in powder form.
The latter is an enzyme extracted from egg white that has proven 80 percent effective against chalkbrood in honeybees.
Current approved treatments for chalkbrood are effective, said Hobbs, but extra tools in the arsenal would be an asset.
As well, pollinators and seed growers must guard against resistance to existing methods.
Bleaching of bee nest matting and incubation equipment is one effective treatment, “our old standby,” said Hobbs. The other effective treatment is paraformaldehyde which, while lethal to chalkbrood, might be dangerous to people who apply it.
Hobbs said the commission hopes to report results of its trials next spring.
Leafcutter bees are widely used in Canada, from west coast to east, but their highest concentration is in the southern Prairies.
They pollinate about 22,000 acres of alfalfa seed crops and about 45,000 acres of hybrid canola seed crops in Alberta.
Leafcutter bees are distributed using gallons as a measurement. One gallon of bees is defined as 10,000 viable bee larvae in dormant bee cell material, said Hobbs. Pollinators of alfalfa crops are paid a percentage of the crop, usually 25 to 35 percent.
For hybrid canola seed crops, companies pay pollinators about $500 per acre, assuming two to three gallons of bees per acre.
