The last time we talked about Fusarium head blight (FHB) was March of 2017. Some parts of that piece will be repeated here. Please note, this is being penned with my farm hat on. I am no expert on crop diseases but when I first saw that ugly pink colour on my 2010 wheat crop, I was motivated to search scientific literature for facts.
This winter, it was my pleasure to attend the Plant Health Summit in Saskatoon, Sask., and other meetings that had very good information on plant diseases and crop rotations. Much good work is being done and there were many excellent sessions.
A University of Saskatchewan colleague provided a literature review paper on FHB by Marcia McMullen from North Dakota State University. For keeners, the citation is, “A Unified Effort to Fight an Enemy of Wheat and Barley: Fusarium Head Blight,” by Marcia McMullen and others, Plant Disease, December 2012, Volume 96, Number 12.
It is a good piece of work and it answered one burning question: What are the environmental variables that “juice up” FHB? About weather and FHB risk they said the best model used “the duration of hours that relative humidity was greater than 90 per cent when temperatures were between 15 and 30 C for the 10 days after anthesis.”
That led me to check out Environment Canada weather data for the Saskatoon airport site to review each day, hour by hour, and count up the number of hours that met the criteria. We now have nine years of data, and a quick look at the data (Table 1 below) shows FHB was an even-numbered-year disease in our area for many years.
With nine years of continuous data, it is clear the criteria as established by decades of work in the United States fits our situation very well. The years 2011 and 2013 were clearly not favourable for FHB development. The year 2015 was intermediate with more risk than 2011 or 2013, however July 2015 saw many days in the grain-growing area with thick smoke from the northern forest fires. The smoke might have been a factor in reducing FHB severity by decreasing NH3 in the atmosphere. Very old literature implicated atmospheric NH3 with plant diseases and smoke might absorb the NH3.
Since 1998, my crop rotation has been wheat, peas, wheat, canola. Wheat was planted on the even years and all went well until 2010 when we had 20 inches of rain and the first appearance of FHB. The Manitoba disease had quickly arrived. The first site of those pinkish-orange heads was frightening. Truth be known it was likely here all along. It just needed the right weather conditions to gear it up.
For me, a switch to FHB moderately-resistant varieties plus application of fungicides were fair band-aids, but they were not a solution to the FHB problem in wheat.
Clearly wheat every other year is too much wheat. By 2016, I switched to barley and managed to grow 83 bushels per acre that went malt — but just under the wire for deoxynivalenol (DON).
In recent years, FHB risk maps have been available in-season and online for Manitoba and Saskatchewan. They provide daily maps of the weather conditions conducive to FHB infection if your wheat is at the vulnerable stage. That information can help prevent unnecessary fungicide applications.
Time for some new ideas
A wheat, peas, wheat, canola rotation has a cereal, oilseed and nitrogen-fixing pulse crop. It all looked good until FHB came along — too much wheat.
Peas were a great rotation option for adding nitrogen, until aphanomyces root rot came along. Recent information suggests that peas even every four years is still not long enough. Some are suggesting we need a six- to eight-year break to control that disease. Plant disease experts expect aphanomyces has been here all along. All it took was us to provide suitable hosts and it did its thing. Plant breeding will help but is not a cure.
Canola is the big money-maker on most farms. Along came clubroot, which was a game changer on some farms. It is not yet a problem on many farms but is spreading. The heartland of clubroot is the areas of Edmonton and Red Deer, Alta.
At the Plant Health Summit, it was my pleasure to listen to Dan Orchard from the Canola Council of Canada and Curtis Henkelmann, who farms in the Edmonton area. They gave a seamless tag-team talk that flowed smoothly and left us with a lot of information. A three-year break seems to be the key for that problem. Rotation has to be accompanied by variety selection, constant field scouting, vigilance in equipment moving and sanitation, and attention to small clubroot patches that may appear. They did leave us with a positive message, albeit not an easy one.
It seems we have painted ourselves into a corner with some existing rotations and we need to think outside the box.
Where livestock are a part of the equation, a three- to five-year break with a forage crop can fill the bill. On many farms that would require a partnership between cowboys and stubble jumpers. As I have said before that is already happening in a few places.
Intercropping with two crops in the same field area is beginning. Lana Shaw from the Southeast Research Farm has been working on this for the past few years with much interesting data. The Rosengren farm at Midale and Axten farm at Minton, Sask., have been leaders.
Two crops at the same time can be challenging for herbicide and fungicide choices but if it works there may be a reduced need for those inputs. There are many variations on the theme, but peas and canola and flax and chickpeas have worked for some farmers.
Peas and canola (peaola) was a common practice in several areas in the 1970s and 1980s when peas were first coming on. The big driver then was the canola held up the peas so they could be harvested. Early pea varieties quickly ended up flat on the ground about harvest time.
Bill Cooper (first president of the then Saskatchewan Canola Growers Association) told me how they did it. The peas were planted as normal and then canola was broadcast and harrowed in. The mixture was harvested and hauled straight to the elevator, which separated the two and paid for each crop.
Perhaps we need to broaden our thinking. It’s not likely we are going to broadcast a canola seed that we pay $600 per bushel for. Perhaps we need to go back to some of the old varieties. With seed at $10–$12 per bushel, we could afford to put on enough seed to get a stand at a very low seed cost. At the U of S, we grew 65 bushels per acre of Tower Canola in 1978 in small-plot irrigation work. Anytime we can get away with less glyphosate the better. Tower was the first canola variety (i.e. rapeseed) with low erucic acid and low glucosinolate became canola.
Maybe we need to start thinking outside the box.
Do not get me wrong — fungicides do have a place but they are not a magic bullet in many situations. I had a pea crop saved by a timely application of Priaxor. We had the check strip to prove it. Peas stayed nice and white and were swathed at the speed of canola until the check strip came along. The check strip peas were brown and a nightmare to swath.
However, for many of our disease problems fungicides are a useful band-aid, but in the long run I think we need to look at more options.
Cycles cycles cycles
Our industry goes through cycles — many of them dictated by the weather. Many of our disease problems are linked to weather and wet weather is the big culprit. Maybe by the time we get our new rotations worked out Mother Nature will have turned off the tap and all these problems will go away by themselves.
A quick look at Table 1 shows that FHB hours have been way down in our area for the past three years. Long dry spells were common. Let us hope the dry cycle does not get well established. Drought will be a problem that will make disease look like a walk in the park. Is anyone long enough in the tooth to remember 2001/02, 1987/88, 1960/61?