This causal agent of root rot is now widely distributed across Alberta. Research taking place in 2017 could eventually be the basis for an effective Aphanomyces risk assessment tool.

Alberta pea and lentil growers have long been accustomed to dealing with root rot. Recent years, however, have brought a game-changing new development.

It had long been believed that fusarium is the main causal agent of root rot in this province. Beginning in 2012, it emerged that Aphanomyces euteiches is another source of root rot, quite different from fusarium and potentially devastating in peas and lentils.

Between 2014 and 2016, disease surveys found that Aphanomyces is present in up to half of Alberta’s pea and lentil fields, with potential annual economic losses of $30 million in peas alone.

Despite the serious challenge posed by Aphanomyces, there’s a lot that scientists and agronomists don’t know about it. During 2017, Syama Chatterton will be working on a one-year research project examining how Aphanomyces infects peas and lentils. This work is supported by Alberta Pulse Growers through the Alberta Crop Industry Development Fund.

“This is a project that I started two years ago in Saskatchewan,” said Chatterton, Plant Pathologist with Agriculture and Agri-Food Canada in Lethbridge. “The question we want to answer is, how many oospores of Aphanomyces does it take to get the disease going?”

The role of soil characteristics

As Chatterton explains, one way to approach this question is to add Aphanomyces when you plant peas and watch what happens.

She’s also looking for any link between soil characteristics and the development of root rot via Aphanomyces. Based on her Saskatchewan experience, she believes there might be a connection. Soil conditions, however, are quite different between Saskatchewan and the different pea-growing regions of Alberta.

“We will be collecting soil from Lethbridge, Lacombe and Brooks,” Chatterton said, “and will see what happens if we add Aphanomyces oospores. It varies by location. Most exciting is that we’ve found that, in a particular field close to Lethbridge, no matter how many spores are present in the soil, we don’t get the disease.”

Today, root rots associated with Aphanomyces are one of the most significant threats to pea and lentil production in Alberta. In severe cases, this disease can reduce yields by 10% to 30%. If soil conditions indicated that Aphanomyces could be a significant issue in a given field in a given year, the producer could plant something else and avoid this risk.

In the long run, understanding the soil/disease connection could unlock new ways for producers to manage Aphanomyces-caused root rots or, in a worse-case scenario, make an informed judgment to avoid pulses for a while. The work being done by Chatterton this year could one day offer these management approaches to growers.

“Before we can develop detection methods, we need to know how many oospores are needed to start the disease, and how much is in the soil,” Chatterton said. “I think this is the foundational research that all future Aphanomyces research will build on.”

Project at a glance

Project title:                Validation of infectivity model for Aphanomyces euteiches for Alberta

Project lead:                Syama Chatterton, Agriculture and Agri-Food Canada

Total value of project: $168,870

Start date:                   November 2016

Completion date:        December 2017

If root rot’s keeping you from growing peas, when is it safe to plant them again? This research project aims to cut weeks off the conventional testing process.

How’s the oil in your truck today? It’s easy to find out and you can do so in seconds. Remove the dipstick, wipe it off, replace it and have a look. Everything you need to know is right there. If only disease prediction in pulse crops was this straightforward.

Syama Chatterton wants to make disease prediction more user-friendly, specifically for Aphanomyces, a causal agent of root rots in peas and lentils.

“Currently the only management recommendation is extended rotation away from peas,” said Chatterton, Plant Pathologist with Agriculture and Agri-Food Canada in Lethbridge. “But, how do you know when it’s safe to plant them again? The idea is to measure the amount of Aphanomyces in soil to know whether it’s okay to plant peas or lentils.”

The traditional method is to conduct bioassays in a greenhouse, a process that normally takes five or six weeks. That’s far too long to be of value to a producer who needs to make pre-planting cropping decisions.

In 2016, with funding support from Alberta Pulse Growers, Chatterton and colleague Claudia Sheedy set out to develop an Aphanomyces detection method that’s accurate and far quicker.

Field work beginning this year

The spark for this research idea came from work done by Sheedy on Aphanomyces antibodies. From this basis, Chatterton and Sheedy are working on a real-time immuno-PCR assay that measures the DNA of the pathogen.

“It is difficult to develop a test because it’s hard to get it to be specific enough,” Chatterton said, “so we are working on the specificity and sensitivity of this test method. It’s working well, with very good sensitivity, and can detect low levels of Aphanomyces.”

In 2017, Chatterton will move beyond the greenhouse to see how well the immuno-PCR assay for Aphanomyces works in the field. Soil will be sampled and tested with the immuno-PCR assay. These findings will be double-checked for accuracy at a plant health lab. If the accuracy of the immuno-PCR assay can be validated, it could eventually lead to an in-field detection tool that could be used by a consulting agronomist or even an individual grower.

The risk associated with root rots has caused many Alberta growers to remove peas from their crop rotation. That’s regrettable on several levels, including short-term farm profitability, long-term soil health and climate impact. If growers had an easier way to measure Aphanomyces, they could get back in peas just as soon as the risk is low enough. Syama Chatterton’s work is helping to make this possible.

“The hardest part of this is the extraction of spores from the soil,” she said. “So, it won’t be like checking oil on a dipstick test, but we are getting one step closer.”

Project at a glance

Project title:                Development on an immuno-PCR for the detection of pea root rot causal agent Aphanomyces euteiches

Project lead:                Syama Chatterton, Agriculture and Agri-Food Canada

Total value of project: $350,000

Start date:                   May 2, 2016

Completion date:        December 31, 2018

Over the next three years, this scientist will study how this disease develops under Alberta conditions. The goal is more effective chocolate spot management.

If Alberta wants to be a globally significant location for faba bean production, we’ll need to come to grips with a disease that the world’s top producers have struggled with for years.

“Chocolate spot (Botrytis fabae) is a historical disease of faba bean, and in fact, is the number-one disease of faba bean worldwide,” said Syama Chatterton, Lethbridge-based Plant Pathologist with Agriculture and Agri-Food Canada. “We haven’t seen the same extent of chocolate spot as other countries, but we know that as faba bean acres increase, the disease is likely to increase as well, so it’s important to try to get ahead of the curve.”

There’s a wealth of chocolate spot management information developed by market leaders such as Egypt and Australia. As Chatterton sees it, much of this information is of little value to Alberta growers. Climatic conditions are different here and Alberta grows different faba bean varieties than these other jurisdictions.

The good news is, within the next few years, we should know much more about how chocolate spot works under Alberta conditions. Chatterton, with funding from Alberta Pulse Growers, recently began a multi-year research project with chocolate spot of faba bean as its focus.

From greenhouse to field and back again

In 2017, Chatterton and her team will place greenhouse-grown faba bean in fields as a ‘trap plant’ to attract chocolate spot. Once plants are infected, they go back to the greenhouse where disease development can be observed in detail.

“We will put out plants every three or four days,” Chatterton said. “There’s a lot of shifting plants in and out of the greenhouse.”

While some fungicides are registered for faba bean in Western Canada, chocolate spot isn’t currently on any label. This project will help build a body of data that could one day support a registration, giving growers a valuable agronomic tool they don’t currently have.

“The right time to apply a fungicide is when the pathogen is active and the faba beans are susceptible,” Chatterton said. “So first, we need to understand the pathogen and when is the most infectious time for it.”

The study moves into a second phase beginning next year. In 2018 and 2019, Chatterton will perform greenhouse-controlled environmental studies to learn more about the response of chocolate spot to temperature, humidity and leaf wetness. It’s all part of a research program producing findings that should help Alberta faba bean growers boost their production in the years to come.

“We haven’t had big issues yet with chocolate spot, but we know it’s coming,” said Chatterton. “We are trying to build our knowledge of the environmental conditions associated with chocolate spot and faba bean. Longer term, we can use that knowledge to develop tools that will help growers.”

Project at a glance

Project title:                Epidemiology of chocolate spot of faba bean

Project lead:                Syama Chatterton, Agriculture and Agri-Food Canada

Total value of project: $835,600

Start date:                   April 1, 2017

Completion date:        March 31, 2020

A large expansion of pea leaf weevil in 2015 made clear that pea and faba bean growers need better ways to deal with this insect.

It was the third week of April when Hector Carcamo saw his first pea leaf weevil of 2017, in his own garden.

For Carcamo, Lethbridge-based Research Scientist, Insect Pest Management, with Agriculture and Agri-Food Canada, the backyard appearance by this pest heralded the start of a busy research year.

With funding support from Alberta Pulse Growers, he’s now entering the second year of a three-year project to study the biology and management of pea leaf weevil in faba beans and field peas.

“In 2015, we saw a very large increase in the intensity and geographic expansion of pea leaf weevil,” Carcamo said. “There previously had been a mild winter, so they were able to overwinter. We counted pea leaf weevil in faba beans at both the pod and flowering stage.”

As Carcamo explains, this study’s first aim is to determine the impact of pea leaf weevil on nodulation and yield of faba bean. The project will also consider whether a foliar insecticide, insecticide seed treatment or both could be effective management strategies. Research plots in Lethbridge and Lacombe are the locations for this work.

“In order to develop a chemical management strategy, we have to look at the biology of the weevil,” Carcamo said, “and gather more information on its feeding and other practices.”

Peas or faba beans: which do weevils prefer?

Carcamo cites previous greenhouse research done elsewhere that showed pea leaf weevil appears to prefer faba beans to peas. If this could be confirmed, it could open up a viable management strategy. Growers could plant a strip of faba beans around a pea field; the insects might stay in the faba beans and steer clear of the peas. Based on his field observations from 2016, however, Carcamo’s now inclined to believe that weevils don’t favour one crop over the other. Work in 2017 and 2018 could change this view, however.

One year of field work has found it’s likely that seeding dates are highly relevant in weevil management. This could form the basis for agronomic recommendations for growers.

“We believe that seeding date can be a huge factor,” Carcamo said. “It’s very clear that peas or faba beans that are seeded earlier have more damage, so there may be an advantage to seeding them later.”

Whether the management strategies proposed by Carcamo involve cultural practices, insecticide application or other tactics, he maintains that growers need to deal with pea leaf weevil in an integrated manner. In the same spirit, this project involves scientists from multiple disciplines.

“Our number one objective in this project is to develop management strategies for pea leaf weevil in faba beans,” Carcamo said. “One should do this research in an integrated manner, making sure that what we do for one pest does not harm another component. We need to use the right tactic for the right pest.”

Project at a glance

Project title:                Biology and management of pea leaf weevil in support of faba bean and field pea production

Project lead:                Hector Carcamo, Agriculture and Agri-Food Canada

Total value of project: $105,562

Start date:                   March 1, 2016

Completion date:        February 28, 2019

Over a three-year period, AAFC scientist Hector Carcamo advanced knowledge around how to protect faba beans from this quality-reducing insect.

Many prairie farmers will associate the insect pest lygus bug with canola. In canola, long-established economic thresholds put growers in a solid position of knowing whether or not to spray.

The growth of faba bean acres in Alberta in recent years resulted in more lygus feeding on this valuable crop. Growers have asked for management strategies to help them fight back, and Agriculture and Agri-Food Canada’s Hector Carcamo took on the challenge.

“Lygus can be significant in some years,” said Carcamo, Lethbridge-based Research Scientist, Insect Pest Management. “Depending on the year, if conditions are right for them, you can have a large population that can be a concern.”

In faba beans, lygus damage tends to be more cosmetic than material. The crop may weigh the same in terms of yield, but lygus feeding produces a dark spot on the faba bean that causes quality and price downgrading in crop for export.

Between 2013 and 2016, with funding support from Alberta Pulse Growers and others, Carcamo conducted research designed to give growers some much-needed information around lygus bug in faba bean.

Survey quantifies lygus in faba

As Carcamo explains, this project attacked the lygus issue from a few directions. “The first thing to do is make sure the damage or the symptoms are caused by the organism you suspect,” he said. “So we dissected the pods and seeds and did a survey in the field.”

Canola growers are accustomed to dealing with one species of lygus. The ones feeding on faba beans could be from a different species and might, therefore, need somewhat different management approaches. A survey conducted by Scott Meers and Shelley Barkley of Alberta Agriculture and Forestry, however, found that the same species of lygus bug that feeds on canola also feeds on faba beans.

“We did a sweep for lygus at 10 spots in each field,” he said. “We found that lygus are most abundant at the pod through flowering stage. The best time to control them could be at early pod, just like with canola.”

This finding suggests that planting faba beans early could help avoid some lygus feeding that occurs later in the season.

Carcamo’s three-year study was intended to build up some basic information on lygus bug in faba beans. Before settling on a formal economic threshold for insecticide application, he believes that more research is needed. Regardless of when an application takes place, Carcamo stresses that growers should take care not to harm pollinators and the natural enemies of lygus. This is important for the ecosystem and for the health of the faba bean crop.

“We are making a preliminary recommendation that if you find fewer than two lygus per sweep, don’t worry,” Carcamo said. “But if you do spray insecticide, keep the bees in mind because their pollination is important for the yield of the faba beans.”

Project at a glance

Project title:               Improving lygus management for current canola and faba bean cultivars

Project lead:                Hector Carcamo, Agriculture and Agri-Food Canada

Total value of project: $192,000

Start date:                   April 1, 2013

Completion date:        November 30, 2016

Here are key findings from four years of work on nitrogen application, seeding rates, herbicide formulations and disease management.

Between 2010 and 2016, the acreage of Clearfield lentils grown in Alberta increased by a factor of seven. With strong global demand for lentils, the province’s growers went all out to meet it.

For most of that period, Robyne Bowness Davidson was working just as diligently to meet farmers’ demands for agronomic information on how best to grow the crop. Between 2012 and 2016, with funding from Alberta Pulse Growers through the Alberta Crop Industry Development Fund, she conducted field research on four core agronomic issues.

Nitrogen application. Pulse crops fix nitrogen so, in general, starter nitrogen shouldn’t be needed, provided the crop is inoculated. This guideline might not apply in the same way with red lentils, however, which have a smaller root system than other pulses. Bowness found that some starter nitrogen is helpful, but too much can hold the crop back.

“They need just a little bit to get them going, until the root system is established and nitrogen can be fixed,” said Bowness Davidson, Lacombe-based Pulse Research Scientist with Alberta Agriculture and Forestry. “But if there’s too much nitrogen, it won’t nodulate. And yes, you need to inoculate.”

Seeding density. Growers in Saskatchewan – old hands at lentils, after all – target 120 plants per square metre. Is this right for Alberta too? Seeding this heavily can be expensive but, as Bowness demonstrated, it’s worth it. “We found that in a year with adequate moisture you can increase the seeding rate and it will increase the yield in a worthwhile way,” she said.

Herbicide formulation. The imidazolinone herbicide family, to which Clearfield lentil varieties are resistant, is available in several formulations. Bowness Davidson studied the effectiveness and crop safety of these formulations and found little difference in weed control and plant health between them.

“Which herbicide formulation is best depends on the year and the soil zone,” she said, “but they are all working.”

Disease management. The fourth element of Bowness’s project was to compare the susceptibility of different Clearfield red lentil varieties to root rots and sclerotinia.

“We wanted to put Clearfield red lentils out there against large green lentils and see whether the disease picture is any different,” she said. “It turns out the diseases are so random, sporadic and climate-dependent that there is no major difference between varieties.”

Should you grow Clearfield red lentils? It’s an agronomic decision with many moving parts. Based on the findings from this project and others, Bowness Davidson developed an information tool that guides growers through 12 questions and helps them land on the right decision for their operation.

With lentil demand surging worldwide, and Alberta farmers equipped with valid agronomic information, Bowness Davidson sees lentils increasing in prominence in growers’ crop rotations.

“Red lentils are now being seen everywhere in Alberta,” Bowness Davidson said. “We need to make sure that farmers can grow these crops. The role of this project was to help them and give them options.”

Project at a glance 

Project title:                Evaluation of the effect of nitrogen rates, seeding rates and herbicide applications on production of Clearfield red lentil in Alberta

Project lead:                Robyne Bowness Davidson, Alberta Agriculture and Forestry

Total value of project:

Start date:                   April 1, 2012

Completion date:        May 31, 2016