ENCHANT, Alta. — Good news for farmers is bad news for researchers interested in studying the pathogens behind blossom blight and stem rot in alfalfa seed crops.
Syama Chatterton, a plant pathology researcher with Agriculture Canada, told the July 23 Alberta Alfalfa Seed Commission tour group that no signs of either disease have been found in seed alfalfa crops this year.
Generally hot and dry weather has kept the moisture-loving diseases away despite known existence of inoculum in the crop, Chatterton said.
Her research is focusing on botrytis cinerea and sclerotinia sclerotiorum.
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The latter is the same pathogen that causes problems in canola, hence the presence of inoculum in southern Alberta where many acres of canola are also grown.
Botrytis can produce spores throughout the growing season that can infect alfalfa flowers and reduce seed production.
“It doesn’t like temperatures over 30 C. That pretty much will kill it,” Chatterton said.
“Between about 22 to 26 degrees, as long as there’s some humidity, that’s really the temperature that it flourishes at.”
Blossom blight has been known to reduce seed yield by 50 to 100 percent under extended cool, wet conditions, according to research by Faye Dokken-Bouchard of Saskatchewan Agriculture.
“Risk is higher when using rotations with canola and borage, but risk decreases when conditions become hot and dry,” she said in a research paper.
Sclerotinia is most dangerous to alfalfa in a two-week period in early July if there are favourable conditions. It requires five to seven days of continuous moisture under crop canopy to germinate the apothecia that produce spores.
Sclerotinia will have more impact on yield than botrytis, Chatterton said.
Sclerotinia manifests itself in alfalfa as white or grey fuzz growing along the stems at the base of the canopy.
Chatterton said she is working on a project that will take air samples and analyze spores in those samples, which could alert farmers to the likelihood of pathogen infection if weather conditions are favourable to disease.
She said such systems exist in other countries.
The available fungicides are preventive, so advance notice of likely infection could save farmers from a yield-robbing disease problem.
Chatterton is also studying pollen to see whether it plays a role in disease transmission. The prevailing opinion is that infected pollen cannot spread disease.
“It’s an area that really hasn’t been explored at all,” she said.
“It might be a non-starter or we might find something new.”
