MEDICINE HAT – Farmers will need to be on guard against several pulse crop diseases this year, says an Alberta Agriculture plant pathologist.
Ron Howard said Canadian pulse crop disease threats for this year include anthracnose on lentils and dry beans, Stemphylium blight on lentils and bacterial wilt in beans and peas.
External pulse crop threats, those that could cause problems if they become established in Canada, include Asian soybean rust and bean and pea viruses.
Howard said anthracnose in lentils first came to his attention in Manitoba, where it’s warmer and more humid than Alberta.
Read Also
VIDEO: Green Lightning and Nytro Ag win sustainability innovation award
Nytro Ag Corp and Green Lightning recieved an innovation award at Ag in Motion 2025 for the Green Lightning Nitrogen Machine, which converts atmospheric nitrogen into a plant-usable form.
“What this disease does is cause leaf spots that quickly consume the foliage,” he said.
“You end up with bare patches in the field. The lesions have spore-containing structures that produce spores that are splash dispersed. This can be a very explosive disease.”
Infested seed is the main way for lentil anthracnose to travel, so farmers should be diligent when buying seed.
Howard said anthracnose in dry beans is becoming more of a problem in Manitoba and is moving into the irrigated bean area in Saskatchewan.
“It’s a fungal disease that causes lesions on the pods and blemishes on the seed. It’s a seed borne disease,” he said.
“Fortunately, we get most of our bean seed out of Idaho and they have pretty stringent conditions for seed production. But as we develop a prairie seed bean industry here, there’s a possibility that we could see this disease move into the western provinces.”
Howard said producers occasionally see anthracnose in Alberta late in the season, but it shows up too late to do any damage. However, new strains are evolving.
“There’s four or five major strains of this pathogen and if strains evolve that are more adapted to our conditions here, this could be a disease we could see more of.”
Howard said Stemphylium blight has appeared recently.
“It’s a leaf spotting disease that might be confused with other leaf spots we see on lentil. The end result is lesions on the leaves and pods, with the plants partially defoliated,” he said.
“At the present time, it seems to be a weather related disease, liking moist growing conditions.”
The fungus Stemphylium botryosum causes Stemphylium blight.
Bacterial wilt in beans is not a new disease.
It’s been around for a number of years in the United States, but in certain years can be a problem on the Prairies.
“A bacteria wilts the plants and they die,” Howard said.
“It also discolours the seed, either purple, orange or yellow. These colourations are caused by different strains attacking the beans.”
In the past couple of years, this disease has become more important in areas of the United States and it has been reported in Saskatchewan and Manitoba.
“Whether this will become a serious problem for us remains to be seen. Right now it’s been sporadic, but it has the potential to spread quickly through bean crops,” Howard said.
Another problematic bacteria is pink seed, which causes seeds to turn pink instead of purple, orange or yellow.
“When we first saw it, it looked like an oddity, but it has been found in peas and other crops, as well,” he said.
“In wet years, pink seed might be a disease that we’re going to see more of in our beans.”
While Asian soybean rust has made headlines across the southern U.S., Howard said researchers are not yet sure if it will be a threat in Western Canada.
“We’re having a close look at it. It can attack soybeans or common beans,” he said.
“Asian soybean rust has two fungal species that cause it. It was first described in Japan in the early 1900s and since then has spread throughout Asia. Airborne wind currents seem to play a major role in the spread of this rust.”
Howard said it’s an aggressive rust, with 10 to 90 percent yield losses reported in susceptible varieties. It has just recently been described as infecting dry beans in the U.S. He’s not sure how serious that’s going to be, but the potential is there.
“Early stage symptoms include yellowish or chlorotic lesions around the points where the spores land on the leaves. Eventually these lesions enlarge, become rusty in appearance, then break open to release the spores. The foliage get rusted and the leaves begin to die,” he said.
“I think it will be a while before soybean arrives and I’m not sure if it will ever be a significant problem for us. But the potential is there and it’s one we’re watching.
“Our concern in Alberta is whether this could pose a risk to our dry edible beans. We don’t have a big soybean acreage here, but Manitoba has a large soybean acreage and if the disease gets established there, it could move from the east to Alberta.”
The disease was first reported in the U.S. in 2004 in Florida. By 2006, 15 states had soybean rust and it’s moving north.
“It can infect over 90 species of legumes,” Howard said.
“A lot of these have been done under artificial conditions in labs, but the potential is there. It spreads readily with airborne spores. They can go hundreds or thousands of kilometres with a single storm front.”
No effective resistance exists for soybean varieties, although breeding is underway.
Several foliar fungicides registered in the U.S. and Canada have provided a stopgap measure.
The U.S. Department of Agriculture established a national disease surveillance system in 2005. Ontario joined the group in 2005 and the prairie provinces joined in 2006.
Three bean viruses – bean common mosaic, bean yellow mosaic and curly top – may one day cause trouble for western Canadian pulse growers. Howard said he’s also watching for at least three potential pea viruses.
“As weather patterns change and conditions get warmer, you see more virus diseases. One reason for that is a lot of these viruses are spread by insects. Under dry, warm conditions, the insects reproduce better, they fly further and they bring these viruses along and spread them around,” he said.
“Bean virus diseases tend to cause discolourations, undersized leaves and puckering. They’re systemic infections and usually get into the plant through infected seed or insect vectors. We see them off and on but they’re fairly rare.”
