All pulse crops are susceptible to the disease, which makes crop and field choice an important consideration for farmers
A show of hands in the room indicated most growers and agronomists experienced root rot last year and are concerned about it this year.
“Root rot is the biggest issue right now facing farmers,” Sherrilyn Phelps of Saskatchewan Pulse Growers said during CropSphere in Saskatoon Jan. 13.
“In order to plan going forward, we have to step into our time capsule, take a look a little bit back and see what we can learn.… Definitely environment was key, any time conditions were wet or you had a high water holding capacity in your soils, such as heavier land, compacted areas or wetter areas of the field.”
Side hill seep, where water moves through the soil from the top of a hill down the side, was common last year affecting large and small patches of ground.
“You as a producer or agronomist may not notice the excess water, but the roots do,” said Phelps, an agronomy and seed program manager.
“Peas don’t like wet feet.”
She said continuous wet springs since 2010 have stressed plants and led to widespread root rot. The plants display symptoms of stunting, yellowing, poor root growth, little nodulation and browning of root area.
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Phelps said the biggest thing learned from last year’s widespread root rot was probably that rotation is a must.
“Rotation is the main factor that causes the increase in hosts in the field, along with the wet conditions,” she said.
“What we found in 2014 is a lot of the poor fields was related to shorter rotations, where peas are grown every second year or third year. You could have had one in 2010, one in 2012 and 2014, so you could have had three peas (or lentils) crops that were grown in a two-year rotation under wet conditions that really helped to increase the amount of the pathogen in the soil.”
The record bumper crop in 2013 may also have contributed to poorer yields last year.
“You took a lot of nutrients off (2013), and there was very little nitrogen mineralization that occurred,” she said.
“A lot of the soil tests coming off of these fields were showing single digits going into 2014, and that’s a concern.”
This year is looking more promising because yields were not as high last year, there was fall moisture and soil test results are showing higher nutrient levels. However, environment is going to determine the growing season.
She said planning for 2015 is all about prevention because there are no quick fixes with root rot. Disease pathogens include fusarium, phythium and rhizoctonia, but the newly discovered aphanomyces is the worst and widespread across Sask-atchewan.
Crop choice is one prevention option.
All pulse crops are susceptible to root rot organisms, but fababeans, chickpeas and soybeans have better partial resistance to aphanomyces in wetter soils compared to field peas and lentils.
Field choice is another option: lighter land with good drainage and managed compaction.
Rotation is the most important way to minimize root rot pathogens and one of the most effective management strategies.
“If you have fields that are positive for aphanomyces, you should be looking at least a six year rotation,” she said.
“Normal rotations with your other root rot pathogens, you have other strategies for managing them, such as seed treatments that will help, so four year rotations are OK.”
Plant health is another key prevention strategy, which includes looking at nutrition, seed viability and other stresses.
Knowing fertility levels might prompt producers to apply 10 pounds of starter nitrogen if soil tests are below 15 lb. of available nitrogen.
Starter phosphate should be applied if seeding early into cool soil.
Inoculations and formulations can affect crop health, as can seed quality: germination, vigour, disease and thousand kernel weight numbers.
Slowing the auger, using a belt auger and watching wind speeds can minimize damage to seed during handling.
Also, rolling when conditions are too wet and cool will stress peas and lentils with over-compaction. Poor timing and water volume during herbicide applications can cause additional stresses.
“Having healthy plants coming out of the ground and healthy vigorous seedlings is really, really foremost in trying to prevent disease,” she said.
“Anything that you can do to ensure healthy plants, vigorous seedlings and growth is going to better enable the plant to fight some of these pathogens. Root rots are really a factor of additional stresses…. It’s all the individual things that can add up, and we can manage each individual thing on its own as we move forward.”
william.dekay@producer.com
