South East Research Farm has researched aphanomyces in pea and lentil crops for five years, but solutions remain elusive
The South East Research Farm near Redvers, Sask., is struggling to find answers to aphanomyces, commonly known as root rot, in pea and lentil crops.
The disease is a large issue for pulse growers who don’t want to wait eight years in their crop rotations after seeding peas or lentils to seed them again.
The South East Research Farm is trying to figure out the disease. A large portion of the research there is dedicated to the study and researchers displayed their work with a farm tour July 28.
They are using natural (derived from natural sources) and biological (living organisms) control techniques to try to slow root rot.
Lana Shaw, research manager for the Redvers farm, said it’s the fifth year they have been researching aphanomyces, and still don’t have any “feasible means of eliminating it.”
“Most of the interesting things going on this year, a lot of it has to do with diseases,” said Shaw. “I have an intercrop trial that has very severe root rot, aphanomyces root rot, to the point some might not produce any seed at all.”
The trials at the South East Research Farm have seen a lot of rain this growing season, which fosters the disease. Shaw said 430 millimetres of rain have fallen since May 1.
“The root diseases have been severe this year. We’ve been able to get some really good information on that. But in some cases, it’s so severe that it’s killed the trials.”
Soil amendments and seed treatments, such as lime fertilizer, have had limited success, but Shaw said those are small gains.
“If we can start adding up things that help 20 percent, then you might end up with a few small hammers to deal with aphanomyces because we don’t have any big ones.”
Shaw and the farm have also been intercropping and using pulse variety rotations to try to reduce the disease, but trial testing is still early in development.
Michelle Hubbard, a research scientist in pulse pathology for Agriculture Canada, has studied the disease, but solutions remain distant.
“I would love to say, ‘yes, (we found a solution)’, but other than long crop rotations and avoiding high-risk fields, those are really the only things.”
Some studies have tried mixing disease-resistant pulses into rotations, but they found they can be infected with aphanomyces as well, possibly a different strain.
Hubbard said the disease is different than others because it deals with oospores underground, which lie dormant until they can infect a desirable host. The disease will use the host to germinate and create more oospores.
“These oospores are so tough and can survive for so long,” said Hubbard. “And they are in the soil, so foliar application isn’t going to work. Genetic resistance is complicated because there’s no gene for gene major resistance.”
Genetically modified varieties have seen the best results so far, according to Hubbard.
Implementing lime fertilizer modifies the pH levels of the soil and has shown results, interfering with aphanomyces oospore germination by making the soil less acidic and adding calcium.
Last year’s trials showed lime reduced aphanomyces, but increased fusarium root rot, a strange occurrence considering root rot diseases usually work together.
“Maybe aphanomyces is being knocked back, but the fusarium is filling that void. It’s a little early to know if that’s really what’s happening, but it’s interesting to see,” said Hubbard.
Another challenge to applying lime is whether the amount needed is reasonable for farmers.
Hubbard said nearly all potential solutions are difficult to apply, but researchers are first trying to find something that is effective before they worry about application.
“Getting reliable DNA samples out of the soil from oospores is challenging. Just knowing what you have based on soil rather than plants is difficult. There’s a whole bunch of really challenging things about it,” said Hubbard.
