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Fabas: residues and don’ts

Check your herbicide history before seeding those sensitive fabas this spring


Judging from the tweets I read and the phone calls I received during and after Saskatoon’s Crop Production Week in January, fababean fever has hit Saskatchewan much like it hit Alberta about a year ago. It’s not very often that Albertans get to give their eastern neighbours tips on producing pulses, but it seems that the general flow of knowledge on this crop is west to east. General fababean agronomics have been covered recently in these pages, but I wanted to touch on a specific topic.

With acres approximately tripling in Alberta between 2013 and 2014, there were a lot of opportunities for farmers, agronomists and scientists to learn more about faba beans. As Mark Olson, pulse crop researcher at Alberta Agriculture said recently, “We’re learning with everyone else. I’ve never ran across 95 per cent of these weird things we see in the fields.”

These “weird” things include the affects of chemical residue, which don’t show up in research trials because the plots are planned with longer intervals between herbicides and sensitive crops.

In the field, however, sometimes herbicide history is overlooked or the complex relationship of soil pH, organic matter and moisture leads to unexpected results.

In the field

I had this experience in one of my fields of fababeans last year. We seeded our beans into a field that had been treated with Curtail M in 2013. I knew from a presentation that Olson and his colleague, Robynne Bowness, gave that clopyralid (the active ingredient in Curtail M) could be harmful to fababeans, but I overlooked this fact when it came time to seed my beans.

We did have a decent amount of rain in 2013 — about 174 mm — which probably saved our bacon. Overall the crop stand was healthy and yielded fairly well, except in the corners and around an oil well, where I assume the sprayer doubled up the Curtail M application. The plants in those areas started out healthy, but began twisting, perhaps as they reached the level to where the residue had washed down. Those areas were grass green when we combined the rest of the field.

And while the yield, in my opinion, was fairly good for the year we had, there is no way of knowing if the crop would have produced more if there hadn’t been that history of residual chemical.

There’s several chemicals to be concerned about when seeding fababeans and you won’t find mention of fababeans in the crop protection blue book, because there haven’t been enough acres to warrant research from the chemical companies. Most producers have probably followed field pea re-cropping restrictions, but Olson and others think it might be safer to follow the restrictions for lentils when seeding faba beans.

“I would say the sensitivity [of fababeans] is similar to lentils,” said Olson. “I don’t have a big body of research to support that, but that’s the consensus from talking to farmers and agronomists.”

This means if you’ve sprayed a herbicide like Infinity in your cereal crop, you’d probably be safe to seed peas 10 months later (if you’re in the black, gray-wooded or dark brown soil zone), but if you’re seeding lentils — and by this argument, faba beans — you should wait 22 months. Again, this is not based on repeatable research trials — which hopefully will be undertaken by the crop protection industry as faba bean acreage increases — but on anecdotal experience. Considering there’s nothing a farmer can do once his or her seeds are in ground with chemical residue, it’s better to be safe than sorry.

This year I double-checked my herbicide history when making my crop plan. We planned to seed faba beans on Invigor canola stubble that had a glyphosate pre-burn, so no worries there. My concern was the Prestige XC (which contains clopyralid as well) that I applied to wheat in 2013. The blue book says “if drought conditions are experienced during the months of June to August inclusive in the year of application (less than 140 mm of rain between June 1 and August 31 or less than 175 mm in the whole year), delay seeding field peas an additional 12 months (22 months following application).”

As mentioned, we had 174 mm between June and August of 2013; 251 mm between June and August of 2014 and 447 mm in all of 2014. With the full 22 months and that much moisture between fababeans and the Prestige XC, I am going ahead as planned.

Until we have verified re-cropping restrictions, Olson suggests considering moisture, soil organic matter, temperature, and application rate of residual herbicide when choosing a field.


Germination and disease

seedlings on display

photo: Courtesy of 20/20 Seed Labs

2014 saw early frost and snow in much of the fababean growing area of Alberta. This meant compromised quality. Some growers had a lot of black or dark grey beans amongst the typical off white colour fababeans.

According to Joanna Cathcart, germination analyst at 20/20 Seed Labs in Nisku, Alta., the range of germination results tells the story of weather challenges in the Alberta last year. The average germination for all fababeans samples submitted to the lab was in the 70s, with some as low as 10 per cent and others in the 90s.

Some growers found that by colour sorting by hand and removing the dark seeds from a sample, the germination results improved 30 to 40 per cent. Whether this is economical really depends on the situation. If all the beans were going as feed then cutting them in half to save some for seed might be a worthwhile option. If you’re giving up human edible grade pricing and end up with a bunch of screenings that can only go for feed, the value in cleaning the beans may be lost.

Whatever you decide to do, be prepared to wait a bit longer than usual for germination results from the lab. As Cathcart explained, her laboratory is accredited by the Canadian Food Inspection Agency (CFIA) and therefore must use the approved crop testing methods as determined by the CFIA.

“Each crop type has specific requirements for temperature, media and testing period,” said Cathcart. Technicians usually test cereals between paper and the final germination count is done at seven days. Fababeans are typically tested in sand and technicians tally results after 14 days.

“Because they are a larger seed they do typically require more moisture and it can be easier to maintain that moisture level in a consistent way by using sand than a paper media,” said Cathcart.

The germination report will list what per cent of seeds had normal germination, abnormal or were dead. In my experience, it’s not unusual to see a higher percentage of “abnormal” seedlings in a faba bean lot than in other crops. Often the abnormal rate will be accompanied by a note saying “mechanical damage suspected.” Fabas are more susceptible than even peas to the blows combines, augers or seed cleaning plants.

“An abnormal seedling has initiated growth but has a critical defect on either its root or shoot system that will cause it to not produce a normal, healthy plant,” explained Cathcart.

Of course, mechanical damage is just one cause of poor germinating fababean seed. Disease can be another factor. Trevor Blois, disease diagnostician at 20/20 Seed Labs, mentioned a number of diseases he observed at varying levels on this year’s seed lots, including: botrytis, fusarium, sclerotinia and stemphylium blight. Botrytis can manifest itself on plant foliage and is commonly known as chocolate spot. Blois said most seed lots are below one per cent disease infection.

Most growers treat seed with a fungicide that controls most if not all of the above diseases. If you’re curious about how your seed will germinate when treated, ask the technicians to find out.

About the author

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Sarah Weigum

Sarah Weigum grows pedigreed seed and writes at Three Hills, Alta.

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