Fighting Fusarium Head Blight

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Fusarium head blight damage in wheat. (Photo: Kelly Turkington)

Cereal growers in Alberta have a new weapon in the fight against fusarium head blight (FHB). It’s an online risk assessment tool that helps farmers and agronomists decide whether to apply fungicides based on the likelihood of the disease turning up in their area.

Brian Kennedy, grower relations and extension manager for the Alberta Wheat Commission (AWC), says the tool was launched in the summer of 2017 following requests from wheat producers in the province.

“They had been seeing fusarium risk maps from Manitoba and Saskatchewan … and they asked us to develop something,” he says.

The tool was developed for the AWC by numerous partners, including Ralph Wright and Pavel Pytlak from Alberta Climate Information Services, plant pathologist Michael Harding and crop specialist Neil Whatley from Alberta Agriculture and Forestry, and Agriculture and Agri-Food Canada plant disease researcher Kelly Turkington.

“We’ve been lucky [in that] we’ve had a couple of years with lower fusarium head blight, but because this is a weather-related disease, growers need to be aware of it and manage their risk by following best management practices every year,” says Turkington.

“This was really to get something out and available to producers, so they can start looking at gauging the potential risk of fusarium head blight based on weather conditions.”

Turkington says while FHB is a relatively new disease in some areas of the province, the disease risk is more widespread in Alberta than it was a decade ago.

“The pathogen has become more frequently found not only in southern Alberta, where it causes production issues and downgrading and so on, but also outside of that region,” he says.

“We’re at a point now that in a number of areas in Alberta, producers are not so much concerned about introducing the pathogen as they are about effectively managing it so that the impact on yield and especially grade and also mycotoxin contamination is mitigated as best possible.”

Weather Station Data

The FHB risk assessment tool works by pulling data from weather stations across Alberta to provide a localized risk warning gauge. This data consists of nearly 130,000 hourly weather observations that Alberta Climate Information Services collects every day from over 370 stations provincewide.

“We think it’s a great use of the data that the weather stations are collecting,” says Kennedy.

The disease severity is calculated on a Manitoba FHB risk assessment model that’s based on air temperature, relative humidity and rainfall over the previous seven days. The Alberta tool is active between June 1 and August 15 each summer, the time when a wheat crop is most susceptible to FHB infection and corresponding losses, both in terms of yield and quality.

The tool, which is designed to be viewed on mobile devices, can be found at agriculture.alberta.ca/acis/fusarium-risk-tool.jsp. The website also includes best management practices for controlling fusarium head blight.

To access the FHB risk gauge, users click on a red pin in the top left corner which opens up a map of Alberta with all of the weather stations marked with a green dot. They can then zoom in and click on the green dot closest to their field, which then brings up the risk gauge for that location.

“A farmer can look at the weather station closest to their field and keep an eye on that, and when they see that it is high risk and their crop is in the floret stage when it’s liable to be infected, then they can make a decision on whether or not to apply a fungicide,” says Kennedy.

Turkington says for some producers, “having this additional piece of information provides some peace of mind.”

Kennedy points out that wheat farmers who apply fungicides regularly to guard against FHB infection can save money with the tool by not having to spray as often. By only spraying when the FHB risk is highest, he says, “this also mitigates the risk of resistance building up in the fungus.”

Kennedy says he has heard good things about the FHB risk assessment system from growers across the province. “They see it as a useful tool.”

Kennedy cautions that weather isn’t the only consideration when assessing FHB risk. Farmers need to be aware of other risk factors such as:

  • The stage of the crop
  • The level of fusarium infestation in their area
  • The susceptibility of the variety seeded
  • If the seed was infected with fusarium
  • If a seed treatment was used
  • The history of the crop rotation in the field
  • Past stubble and straw management practices

New Features

Kennedy says the system’s developers chose a mobile friendly website rather than an app as a platform for the tool to make it easier to use.

“The advantage for users is they don’t have to install something on their mobile device. We tend to get a lot of apps on our devices that are always updating or sending us reminders, which leads to a lot of them being deleted. So, if this is added to their favourites on their browser on their phone, they can look at it at any time without having to install any software,” he says.

Kennedy notes that a number of new features were added to the tool this past growing season, including pest management recommendations and risk assessment maps for alfalfa weevil, bertha armyworm and wheat midge.

Data related to growing degree days and corn heat units was also added in 2018, and there are discussions about adding more features in 2019, Kennedy says.

According to Turkington, the hope is to update the model for weather predictions in the risk calculations for fusarium head blight.

“The models are continually being refined,” he says. “If you look at some of the recent risk maps in the United States, they’re starting to focus now on mean relative humidity over the previous 14-day period, but it was felt we could start with the model version currently being used in Manitoba, at least in the initial phases of the project and then update as needed.”

Kennedy says more work needs to be done across the entire Prairie region to ground-proof the disease risk assessment models for Western Canada, and that it’ll take a couple of years of scientific study to incorporate weather forecasts into the Alberta FHB tool.

Frost and Nitrate Accumulation

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Many parts of the province have already experienced some frost. Barry Yaremcio, beef and forage specialist at the Alberta Ag-Info Centre, looks at nitrate accumulation in crops and how to manage it.

Nitrate accumulation can become a problem when crops experience light frosts of -1 C to -2 C for even only a few hours during the night. “These conditions damage the leaves of the plants but not the roots. Over the next three of four days, the roots continue to send nutrients up the plant. The damaged plant is unable to use those nutrients, resulting in nitrate accumulation,” explains Yaremcio.

“When we get a heavy frost of -5 to -6 C for six or seven hours, the internal working system of the plant is completely destroyed and it can no longer move water or nutrients. A killing frost means that the plants are dead and therefore nitrates won’t accumulate,” says Yaremcio. “Light frosts that are experienced for only a few hours damage the plant but not the internal bundles that move water and nutrients up the stem. The injured leaves can’t use the nutrients effectively, and that is when there is the greatest chance of nitrate accumulating.”

Annual crops are the most susceptible to nitrate accumulation – oats being the worst – but also barley and wheat. Immature salvage canola crops cut for silage or greenfeed also have a tendency for nitrate accumulation.

“Alfalfa is a legume and the nodules attached to the roots tend to hoard the nitrogen and only release as much as the plants require,” says Yaremcio. “Nitrate accumulation is extremely rare in alfalfa.”

Application of nitrogen fertilizer or manure also has a significant influence on the susceptibility of the crops. High amounts of nitrogen fertilizer or manure increase the risk of nitrate accumulation.

“If fields have been used for swath grazing, winter feeding areas, have had high manure applications or high amounts of fertilizers applied in the spring, those fields are more susceptible to accumulate nitrate in the plants,” says Yaremcio. “If no fertilizer has been applied, or if it is an old grass field, those fields are not typically a problem.”

After a frost, the timing for cutting the field is a key factor in managing nitrogen accumulation. “If producers can get out in the field the day after the frost and cut it as quickly as they can, there should not be a problem,” says Yaremcio. “Nitrate levels increase and peak on the third or fourth day after a frost.”

If there is time for the plants to recover, and there is no additional frost to kill the plants, nitrate levels will decline and return to normal 14 days after the frost.

“It is either get out there within one or two days after the frost and cut very quickly, or wait 10 to 14 days before cutting the field,” says Yaremcio.

For more information, contact the Alberta Ag-Info Centre at 310-FARM (3276).

Source: Alberta Agriculture and Forestry

Frost Hits Canola. Do I Swath?

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This is the question for many canola growers Sept. 4 as frost (in some areas heavy and long-lasting) hit parts of Alberta over night.

Start with these steps:
—Check standing canola the morning after a frost.
—Before taking any action, wait 4-6 hours after frost to allow the full extent of frost damage to become evident. The crop may look undamaged in the morning but by the afternoon wilting, desiccation and pod splitting may begin. This crop may need to be swathed to preserve yield, but keep in mind that high green counts are likely.
—Light to moderate frost damage may take longer to show up. If no damage is evident after the first day and you decide to leave the crop to mature more fully, scout again after 2-3 days to reassess.
—If most or all seed is mature and you planned to swath the day after a frost anyway, then don’t bother waiting 4-6 hours. Just start swathing.

Responses for heavy or light frost

Heavy frost… below -2°C: Assess the damage in early afternoon. Check pods for a white, wilted appearance. Pod shatter and pod drop could begin within a day, especially with warm sunny afternoons. If pods are desiccating rapidly, swathing right away will preserve as much yield as possible.

For canola with high seed moisture, frost in excess of -5°C is generally lethal, resulting in non-viable seed. At such low temperatures, ice crystals physically disrupt structures such as membranes and enzymes. Pods of immature canola crops frozen at lethal temperatures have been observed to turn black, whereas mild frost turns pods white or white-speckled.

Light frost… above -2°C: Hold off swathing. Check in the afternoon for wilting to make sure frost damage was not heavier than expected. You may see some speckling on the stem and pods, but this is of little concern as long as the plant is still alive. If no wilting, leave the crop standing and check daily.

What to look for during daily monitoring:

—If the majority of the seeds remain green and immature, delay swathing to allow for further seed maturity.
—If the pods are severely damaged and are beginning to desiccate, swath during periods of dew or high humidity to reduce the amount of pod shelling and pod drop.


Frost and quality. A killing frost will reduce quality, but that can’t be helped — whether you swath today or wait. Immature seeds (moisture content higher than 20%) will be damaged. Seeds with less than 20% moisture will normally escape damage. Green seed is the major downgrade that results from frost.

Source: Canola Watch

Nitrate Accumulation in Hailed Out Crops

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Hail storms travelling across the province this time of year are definitely not unusual. Subsequent damage to annual and perennial crops can be minimal or complete destruction depending on their severity. Barry Yaremcio, beef and forage specialist at the Alberta Ag-Info Centre, explains what to consider when salvaging damaged cereal, oilseed, or hay crops after a hail event to avoid problems with nitrate accumulation.

“Nitrate accumulation occurs in a plant when it is injured and is not able to convert nitrate to protein efficiently after a hail storm,” explains Yaremcio. “In non-legume crops, water and nutrients are pushed into the plant from the root system as quickly after the storm as was provided prior to the hail event. Nitrate accumulates in the top leaves and concentrations peak roughly four days after the injury. If the plants recover and new growth is observed, nitrate levels can return to normal 12 to 14 days after the injury.”

Soil fertility – in particular the nitrogen content in the soil – and stage of crop development are critical factors as to whether there will be a nitrate problem in the plants. “Crops such as canola and wheat have high amounts of nitrogen fertilizer applied. If the crop is thin and not overly productive, there could be significant amounts on soil nitrogen remaining in the soil into July. A crop that is thick with high yield potential would use up the available nitrogen much earlier in the growing season. With less nitrogen left in the soil, there is less available to be transported into the plant,” says Yaremcio.

Yaremcio adds that hay crops tend to have lower fertility than annual crops. “The risk of a hay stand having high nitrate concerns is much lower. Alfalfa and legume crops have nodules in the root system that regulates nitrate transport into the plants. The nodules only allow as much nitrogen into the plant as is needed, therefore it is extremely rare to have nitrate accumulation in legume forages. Nodules on the roots of legume crops only allow as much nitrogen up into the plant as is required. There is no risk of nitrate accumulation in alfalfa or clovers.”

Forage test labs can test for nitrates. Says Yaremcio, “If the sample is taken the fourth day after the storm, the results will indicate the “worst case” situation. Talk to the lab and request a rush analysis, then the results could be available one to two days after the sample is received.”

Yaremcio explains that ensiling the crop will not reduce nitrate levels if the product is put up properly. “Adequate amounts of packing, sealing with plastic as soon as possible, and allowing the silage to ferment for three to four weeks produces a stable product. Silage that is poorly made can reduce nitrate levels, but the quality of the silage is greatly diminished. To get a representative sample when the silage is being made, take one handful of silage out of each load as the trucks bring it in. Put the handful into a plastic pail with a lid. At the end of the day, mix up the sample and collect a half bread bag full, squeeze out the air and freeze the sample. Send the sample in for analysis on a Monday or Tuesday so it gets to the lab without being in transport over the weekend.”

Find more information about nitrate poisoning and feeding nitrate feeds to livestock. “Nitrate in a forage or silage can be managed so that there are no problems or difficulties encountered during the feeding program,” adds Yaremcio. “Talk to your feed sales person or company nutritionist, nutritional consultant, or contact the Ag-Info Centre talk to a livestock specialist.”

Source: Agriculture and Forestry