The confirmed presence of chocolate spot in Saskatchewan is adding urgency to the search for knowledge about how this disease could occur under Alberta conditions.

Maybe not today, maybe not tomorrow, but it won’t be too many years before chocolate spot is a significant issue for faba bean production in Alberta.

It’s a disease associated with potentially serious yield losses, based on the experience of growers in places such as Australia and Egypt.

Syama Chatterton, a Lethbridge-based Plant Pathologist with Agriculture and Agri-Food Canada, is in the second year of a three-year research study on chocolate spot.

How can you study a disease we don’t have much of yet? Throughout the 2017 growing season, Chatterton and her team of co-op students took greenhouse-grown ‘trap plants’ out to the field every Monday and Thursday for about nine weeks, hoping to attract chocolate spot.

“It’s a lot of work moving plants in and out of the greenhouse every few days,” Chatterton said. “For the most part, it was very successful. Bringing the plants back into the greenhouse was a nice way to monitor spore activity and determine when those infection periods are.”

 Understanding chocolate spot before it becomes a threat

Chatterton’s research is taking place in Lethbridge and Lacombe, monitoring the progression of the disease under different regional conditions. She reports that moving plants back and forth between field and greenhouse, while laborious, yielded important insights. Slowly but surely, Chatterton is assembling a data set that can help pinpoint when infectious periods might occur.

“We weren’t necessarily expecting to see disease risk toward the end of June, but in Lethbridge we surprisingly saw infection periods fairly early in the season,” she said. “While infection peaked at the end of June, then declined because it was so dry in Lethbridge, we saw an opposite pattern in Lacombe. There, no early disease peaks, but it slowly increased toward the end of the season.”

For 2018 and 2019, Chatterton and her team will be back indoors. They’ll be augmenting their field data with greenhouse-controlled environmental studies to see how chocolate spot responds to factors such as humidity and temperature. This could ultimately provide growers with a kind of early warning system.

“We’re matching some of the things we’re seeing outside,” Chatterton said, “like weather conditions and environmental variables that lead to disease and taking it into the greenhouse to determine exactly what the humidity and temperature conditions are that lead to infection.”

Given that chocolate spot is the number-one disease of faba beans worldwide, and Saskatchewan is already dealing with it, Alberta can expect a visit sooner or later.

Chatterton hopes that the information generated by this project will help faba bean growers get out ahead of the disease.

“Seeing chocolate spot in Saskatchewan is a good indication that we are going to have problems in Alberta,” she said. “This project is really important for getting a handle on a disease before we start seeing a problem.”