AgSolutions AdvisorOctober 2016

The rise of Aphanomyces in peas and lentils across Western Canada. Best management practices to reduce risk of infection of aphanomyces root rot.Written by: Allison Friesen

Introduction

Seed- and soil-borne diseases are common occurrences for Canadian pulse growers, especially with the wet weather patterns and tightened pulse rotations of the past few years. But there’s one disease in particular that has recently caught the attention of growers and agronomists alike. Root rot caused by Aphanomyces euteiches is a disease that has been identified across Western Canada and can be quite detrimental in peas and lentils. There is a concern that the growing prevalence and incidence of this disease could potentially have a dramatic impact on pulse acres throughout most of Saskatchewan and parts of Alberta.

Aphanomyces is part of the oomycete family of fungal-like pathogens and is one of the most difficult root rots to control because of its insensitivity to chemical treatments. The pathogen thrives in wet, waterlogged soils where it produces both motile zoospores and sexual oospores. The zoospores “swim” through the soil towards susceptible plants and oospores can survive in the soil for 10 to 20 years, acting as a continuous source of inoculum. Belowground, some of the first symptoms to appear are lower nodulation levels, decreased root masses, and girdled, honey-brown coloured roots. Aboveground symptoms appear 1 to 2 weeks after infection and include yellowing and chlorosis of leaves, stunted growth and seedling death (Figure 1).

Infected

A B C

Non-infected

Figure 1: Above and below ground symptoms of Aphanomyces Root Rot. A. Stunting and yellowing of leaves, B. Caramel colouring of the roots, C. Girdling of the stem.

Source: U of S Cheryl Cho, Dr. Sabine Banniza Lab

Regional considerations

The 2015 growing season was much drier compared to 2014 in Western Canada, which fooled growers into thinking that disease pressure in pulse fields would be lower in 2016. But pulse prices continued to soar and more and more growers are deciding to push their limits with rotations and grow pulses in non-traditional regions. Combined with this, in 2015 we saw a warm fall, a mild winter and an early spring, producing conditions that were conducive for disease development. To top it all off, this past July was an extremely wet month (Figure 2) and as the rain continues, aphanomyces is becoming a very real issue.

Consequences

Aphanomyces can cause devastating crop losses on entire growing regions where field peas, lentils and alfalfa are common rotational crops. This is especially true since there is no effective seed treatment available. It’s been estimated that this disease can cause yield losses of 50 percent or more. We’ve seen examples of this kind of impact in France and the Great Lake Regions of the United States. Inoculum levels have become so high in these regions, that pea production and the processing facilities around them have been relocated to drier areas with better growing conditions.

Best Practices

Despite some seed treatments being introduced to the market for suppression, there is still no effective chemical solution to completely control this disease. However, there are several other steps growers can take to minimize risk in their fields, including lengthening rotations between susceptible crops.

Figure 2: 7-day precipitation map for the Prairie region, July 13-19 – Environment Canada 2016

Field choice

• Choose fields with lighter textured soils and good drainage

• Take peas/lentils out of rotation for 3 years, up to 8 years if aphanomyces is positively identified

• Manage or avoid compacted fields

Soil testing and fertility

• Use starter nitrogen if soils have less than 15 lbs available N per acre in the top 12 inches of soil

• Use phosphorus if seeding early into cool soils

• Test seed quality to ensure best seed lots possible

Seeding decisions

• Use appropriate inoculant to promote nodulation

• Apply seed treatments for other fungal pathogens or if planting early into cool soils

• Choose more resistant crops such as faba beans, chickpeas and soybeans

• Minimize seed damage and watch airspeed of the seeder

• Seed into warm moist soil for quicker emergence and more vigorous seedlings

After seeding

• Scout crop for signs of stress

• Follow herbicide labels as increased injury can occur when plants are stressed

Expert opinion

Aphanomyces has been found worldwide in several pulse growing regions. It was first reported in Canada in the 1930s, but only positively identified in Saskatchewan in 2012. This is supported by Dr. Sabine Banniza from the Department of Plant Sciences at the University of Saskatchewan, who believes the pathogen has only been present for a little over 3 years in Canada. Its impact was not substantial which is why the pathogen went undetected until now. If aphanomyces does develop into a major disease in Western Canada, Dr. Banniza believes it could become a big problem for pea production. Her recommendations include relying on alternative crops that have natural tolerances to aphanomyces. For example, planting chickpeas in lighter, drier soils and using cultivars like CDC Frontier that have partial resistance to the disease.

Future Innovations

There are currently no pea or lentil cultivars available with complete resistance to aphanomyces. However, Dr. Banniza is working with labs in both the US and France to breed lines with resistant traits. Research is being conducted at the University of Saskatchewan and Agriculture and Agri-Food Canada on the infection process and pathogen survival, along with the development of an accurate quantification method from soil samples. BASF is currently working on a seed solution for aphanomyces and it is our top priority to have a product registered as soon as possible to mitigate this disease.

AgSolutions AdvisorOctober 2016

Don’t let storage spoil your season. Strategies for post-harvest pulse storage. Written by: Bryce Geisel

As we finish off harvest and head into winter, it’s important to keep an eye on the moisture and temperature of your pulses as they’re placed into bins. Each bin represents a significant amount of time and money invested through the season, so taking steps to ensure proper storage conditions will help protect your crop.

Not too moist. Not too dry.

Depending on your pulse crop, aim for seed moisture values between 13% and 16% for proper storage. Too dry and you risk seed splitting or cracking, which can greatly reduce your quality.

PULSE CROP STORAGE

Lentils Grain moisture levels targeted at 14% to 16% are needed for safe storage. Aim for 14% in green lentils or 13% in red lentils to improve splitting efficiency later on.

Soybeans Store below 14% seed moisture content.

Field peas Store at 16% moisture content or below.

Dry beans Moisture levels at 16% or lower for grain storage.

Temperature and moisture – spoiler alert.

Which drying system should you use? That depends on your pulse’s moisture content. The airflow rate from natural air drying (NAD) is generally ten times that of aeration, making it an efficient means of reducing seed moisture content. Because pulse harvest tends to occur earlier than other crops, the temperature and humidity of the air are usually still suitable for air drying without the need for added heating. Aeration can cool down the seed but has less of an effect on the seed’s moisture content because cool air won’t dry down seeds that are already cool. Keep in mind that high bin temperatures can also lead to spoilage, even when the pulse crop is dry. Aim for bin temperatures of 15°C or lower. Cooled seeds are also difficult to dry, so be sure to dry down first before cooling and storing.

Airflow rates: Aeration vs. Natural air drying

Aeration = grain conditioning/cooling low airflow rate (0.1-0.2 cfm/bu)

Natural air drying = removing moisture from grain high airflow rate (1-2 cfm/bu)

Source: PAMI. 2013. The facts about grain aeration.

Go with the airflow.

Depending on the rate of airflow, you can also target any inherent variations in temperature and moisture within the bin. Other than the fan used, airflow rate is dependent on static pressure, a measure of the resistance to air flow. This may differ from operation to operation since resistance is determined by seed type, seed depth in the bin, airflow rate and type of distribution system (i.e. ducting).

Moisture and temperature of your seed and air.

When you aerate, bin temperatures will come down as long as the air outside is cooler. But natural air drying can be a little more complicated. It depends on the equilibrium moisture content (EMC) of the air – a point where neither the air nor the seed will absorb any more moisture from each other. Specific to the pulse crop being treated, EMC values are determined based on the air’s temperature and relative humidity. Be aware that these factors can change throughout the day and the minute the air comes into contact with the seed. In fact, the air’s ability to dry also depends on the temperature of the seed. When referring to EMC charts specific to your pulse crop, use them as guidelines for controlling the moisture level of your seed.

Source: Joy Agnew, PAMI. Accessed from <http://www.topcropmanager.com/pulses/maintain-the-value- of-your-pulse-crops-15447>

When to start up your fans.

For aeration fans, PAMI (Prairie Agricultural Machinery Institute) recommends turning them on, and leaving them on, once the ducts are covered and up until the temperature of the seed is safe for storage. For natural air drying fans, PAMI’s recommendations depend on your end goal. See table below.

Goals “Best” NAD fan strategy

Safe storage for all grain types in a variety of ambient conditions

Run fans continuously

Minimal fan hours (grain is only 1-2% above dry) Run fans at night only

Minimal fan hours (grain is more than 1-2% above dry)

Run fans during day only

Uniform moisture content profile (no overdrying) Run fans during day only until average moisture content is 1-2% above dry, then run fans at night until grain is cool (tough grain will dry and over-dry grain will re-wet)

Source: PAMI. 2013. The facts about grain aeration.

Keep an eye on those bins.

Once your seeds are in, be sure to check for hot spots regularly and any changes in moisture or temperature inside the bins. Look out for manual or automated systems that can help you better track bin conditions and even send you the results on your mobile device. Monitor seeds frequently during the first month of storage, as some pulse crops respire or “sweat” and lead to moisture accumulation. You can check less frequently over the winter months when temperatures are less than or equal to 5°C.

References

1. Field pea production tips. Manitoba Pulse and Soybean Growers.

2. Growing pulse crops. Saskatchewan Pulse Growers.

3. Top Crop Manager. 2014. Maintain the value of your pulse crops.

4. PAMI. 2013. The facts about grain aeration.

5. Varieties and management. Alberta Pulse Growers.

AgSolutions AdvisorOctober 2016

Optimizing nitrogen fixation through increased nodulation in peas and lentils Not all pulse inoculants are created equal Written by: Russell Trischuk

Rhizobia and root nodulation – the perfect marriage

If you’re growing soybeans or pulses, you likely know how important root nodulation is to the success of your crop. This means making sure your choice of inoculant is the right one for your crop, and that you get that inoculant to the root system where and when it can do the most good.

Maximizing nodulation requires first having a close look at what is responsible for it, namely the rhizobial bacteria that live in the soil around the roots. Rhizobia are naturally occurring soil bacteria, some of which form mutually beneficial relationships with the roots of pulses and other legumes. This symbiotic relationship leads to nodulation. It’s these nodules that convert nitrogen from the air into ammonium – a form of nitrogen that can be used by the pulse plant. In exchange, the plant provides the rhizobia with the energy, enzymes and oxygen it needs to live. It’s a perfect marriage! But the amount and type of rhizobia that is found naturally in soil almost always need help in order to maximize yield. Inoculants provide that help and making sure they carry the right kind or strain of rhizobia is important to success. In other words, not all pulse inoculants are created equal.

In this article I’ll present an overview of how rhizobia benefit peas and lentils and how different strains effect nodulation and plant biomass. We’ll also look at choosing an inoculant that incorporates strains that are matched to both the crop and typical Canadian growing conditions.

Rhizobia form a mutually beneficial relationship with the roots of pulses, resulting in nodulation.

Different strains of rhizobia give different results

Research has shown that inoculating with different strains of rhizobia on legumes can produce variable results. The amount of nodulation and total shoot weight vary, depending on the strain of rhizobia used. The results can also vary depending on the species of legume, be it peas or lentils for example. To get a handle on how differences can affect a crop let’s look at a study that measured nodulation number and shoot weights, both of which are good indicators for yield potential.

In this data we can see how nodulation varies depending on the strain, for peas and lentils. Nodulation also varies between the plant species; field peas show a higher, more consistent nodulation score than lentils across the strains. For lentils there are fewer, more specific strains that give better results.

Source: Slattery, J.F. and Pearce, D. (2002) Development of elite inoculant Rhizobium strains in southeastern Australia. Australian Centre for International Agricultural Research

The other indicator, total dry weight of the seedlings, also shows a substantial difference across different strains of rhizobia.

Source: Slattery, J.F. and Pearce, D. (2002) Development of elite inoculant Rhizobium strains in southeastern Australia. Australian Centre for International Agricultural Research.

RHIZOBIAL STRAIN

LentilField pea

Nodule Scores

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What’s the impact on grain yield?

So the data in a greenhouse setting shows that different strains of rhizobia give different results in terms of the nodulation and seedling weights being measured as indicators for yield potential. How does this translate into actual yield? And how does that translate into yield in actual growing conditions?

In the same study, final grain yield was also measured. The data shows that the answer was not so straightforward. Good nodulation scores did not always result in higher grain yields. However there were strains that performed better in yield and also produced more nodulation.

The bottom line is that selection of the most efficient and effective rhizobia for producing actual gains in yield potential needs to be made carefully. While increased nodulation is the important first step to increased yields, identifying a strain that is matched to the plant and works well in the conditions where the plant will be growing requires additional steps.

Source: Slattery, J.F. and Pearce, D. (2002) Development of elite inoculant Rhizobium strains in southeastern Australia. Australian Centre for International Agricultural Research

A unique strain for Canadian pulses

In Canada growers have a choice of rhizobial strains for inoculating peas and lentils. The data shown here gives results for a commercially available, unique strain, Rhizobium leguminosarum biovar viciae, strain 1435, compared to another inoculant and an uninoculated control. In peas we see a 6% increase in yield and in lentils, 9%. It’s a good indication that selecting the best rhizobial strain is a lot like matchmaking, and the perfect marriage needs the perfect match.

Choosing the right strain can result in 6% more yield in peas and 9% more yield in lentils.

Source: Third party field data from 87 station years (peas) and 84 station years (lentils). Station years = number of trials x number of years.

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PEAS

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LENTILS

+ 9% over otherinoculant strain

+ 6% over otherinoculant strain

Superior strain inoculantOther inoculant strainUninoculated control

AgSolutions AdvisorOctober 2016

The benefits of pulses in your rotation There’s an added bonus when you include peas or lentils Written by: Russell Trischuk

A lot of right reasons for crop rotation

Every grower understands that planning a sequence of crops that’s appropriate for their fields is fundamental to sustaining healthy production. Alternating between broadleaf and cereals and avoiding growing similar crops year after year in the same field has well-established advantages - better control of weeds and diseases being the major ones. Including pulses in the sequence also provides these advantages, and a bit more.

Different crops have different weed control options in terms of chemistry. Rotating between herbicides that control grasses in broadleaf crops and herbicides that provide broadleaf control in cereals is an important part of managing weed resistance. It’s a familiar refrain that using different modes of action in your sequence is essential for maintaining the diversity that can help improve weed management, including volunteers.

Diversity in crop rotation is also important for managing disease. Different types of crops host different diseases. Since those diseases can persists in the soil and/or on crop residue, growing the same or similar crop in tight rotations increases the risk of providing a host for crop-specific diseases. Blackleg on canola for example can exist in a field for up to 4 years after it’s been present in the crop. Including crops that do not host blackleg, in an extended sequence, helps lower that risk.

Rotating between different crops also has secondary benefits in things like residue management (some crops produced less residue than others) and conserving soil moisture or making production schedules more flexible for seeding and harvest. In short, rotation is a good idea for lots of right reasons.

Managing blackleg in canola requires rotating to other crops that do not host the disease.

Source: AgSolutions® Performance Trials, Western Canada, 2010

A special reason for having pulses in the sequence

Unlike canola and cereals, pulse crops are different in that they get most of their nitrogen through biological fixation of atmospheric nitrogen. In crops like field peas and lentils, for example, the plant nitrogen requirement obtained by fixation can be as high as 80%, representing a significant saving in the cost of fertilizer.

Nitrogen fixation in inoculated pulses grown under irrigation in Southern Alberta

Pulse Plant-N Derived from Atmosphere (%) N Fixed Symbiotically (lb/ac)

Fababean 90 267

Field Pea 80 178

Lentil 80 134

Chickpea 70 108

Dry bean 50 62

Source: Saskatchewan Agriculture and Food, adapted from R.J. Rennie, formerly at Agriculture Canada Research Station, Lethbridge, AB

So, in addition to the rotational benefits in terms of disease and weed management, pulses require less fertilizer, an important consideration in western soils that may be low in nitrogen. But the benefits do not stop within the pulse year itself. Crops that follow a pulse also see benefits. For example cereals that are grown on field pea stubble have been shown to yield more per acre than cereals grown on canola stubble.

Relative yield of crops grown on various stubble types

Stubble Peas Flax Canola Wheat Barley% Yield of check (crop on own stubble = 100%)

Cereal 125 111 152 98 109Other Oilseed 114 109 177 131 138Pea 100 142 196 147 152

Source: Canola Council of Canada, Adapted from Townly-Smith Report to Saskatchewan Pulse Crop Development Board, 1994.

In the above example based on research from the black soil zone taken at Melfort and Aylsham, SK, canola seeded into canola stubble yielded 10% to 20% less than canola seeded into cereal or pulse stubble. Canola seeded into pea stubble had 196% of the check (canola seeded into canola).

Though it’s tempting to make the leap and attribute the increases to nitrogen (N) that’s returned to the soil by pulse residue (and that’s partially true), research on the “magic” of following peas in a rotation, suggests that there are other non-N factors at play.

…no matter how much N you applied to barley grown on wheat stubble, you could not produce the same yield as barley on pea stubble with added N. This indicates what we call a non-N benefit of pea stubble…

Source: Conservation and Pulse Crop Production, Johnston, A., Miller Beckie, H.J. and S.A. Brandt. 1997. Nitrogen contribution of field pea in annual cropping systems. 1. Nitrogen residual effect. Can. J. Plant Sci. 77: 311-322.

Regardless of how canola or cereal crops get their benefits when they follow pulses in a rotation, the fact is that the advantages can be real. So planning to include a healthy and productive pulse crop in the rotation can make a lot of sense.

Maximizing the magic for pulses

As mentioned, pulses get most of their nitrogen through biological fixation. The process depends on a symbiotic association with naturally occurring bacteria called rhizobia found in the soil near the roots. If the rhizobia are the right kind and available in sufficient quantity, this mutually beneficial relationship results in the formation of nodules on the roots. Nodulation is key, in that it’s these nodules where nitrogen is converted into a form that can be used by the plant for increased growth.

In Western Canadian soils, growing pulses successfully usually requires additional inoculation with rhizobia that are matched to the crop. Inoculating with the right strain of rhizobia in substantial enough quantities helps to maximize nodulation. The result is increased nitrogen fixation with higher yield and protein potential. It’s an essential step to make sure that when a pulse is included in your rotation you’ll get all the possible benefits for both that crop and the one that follows.

Source: BASF trials, 2007

When growing pulses in the rotation plan to inoculate for maximized nodulation and nitrogen fixation.

Nodulator XL peasUninoculated peas