What’s Causing the Bleached Heads in My Wheat Crop?

Based on archived post from September 2014

In 2012 and 2014 bleached, white heads showed up in wheat, barley, and oat fields across Manitoba.  It appears the bleached heads are making a reappearance in 2015.

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White heads caused by root rot. (Image: Kansas State University)

There are a number of things that could be the cause:

  1. Insect damage – One of the tests to see if a white head is potentially wheat stem maggot is to try to pull the head out of the stem. If the head pulls out easily, it could be because a larva of wheat stem maggot has severed the stem, resulting in the head turning white. Larvae may be present above the top node.  See Manitoba Agriculture’s website for more information on wheat stem maggot:  http://www.gov.mb.ca/agriculture/crops/insects/wheat-stem-maggot.html
  2. Root rot – infected plants will generally pull free from the soil without much resistance. In years where the plants are under stress due to either lack of moisture or excess moisture, a loss of root tissue from root rots will have a much larger impact.
  3. Fusarium head blight – if seed is produced they are smaller, chalky, and can be shrivelled. Pink or orange mycelium may be visible at the base of the glumes.
  4. Aster yellows – infected plants show white heads, but green stems and seemingly healthy root systems.
  5. Environmental stress – high temperatures, bright sunlight, and hot winds can results in white, empty heads.

Additional information can be found in the July 27, 2012 issue of Manitoba Agriculture’s Manitoba Insect & Disease Report available at: http://www.gov.mb.ca/agriculture/crops/miu/2012/2012-07-27/report.pdf

Submitted by: Pam de Rocquigny, Provincial Cereal Crops Specialist, Manitoba Agriculture

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Understanding the Saskatchewan and Manitoba FHB Risk Maps

Written & Submitted on July 22, 2015 by: Faye Dokken-Bouchard (Plant Disease) and Mitchell Japp (Cereal Crops), Provincial Specialists, Saskatchewan & Pam de Rocquigny, Provincial Cereal Crops Specialist, Manitoba

For the first time in 2015, FHB risk maps are available in both Saskatchewan and Manitoba. At a glance, on a given day the maps may appear to indicate a different risk for growers in each province, which can be concerning for farms along the Manitoba-Saskatchewan border. However, closer examination will reveal minor differences in the models and maps useful for considering FHB risk.

In Saskatchewan, maps are created with models (depending on spring or winter wheat) using temperature and/or relative humidity in the previous 5 days, plus 2 days forecast. While in Manitoba, maps are created with a model that uses the hours of precipitation and the hours with temperatures between 15°C and 30°C during the previous 7 days. Each province then has its own categorization based on slightly different threshold values – low, moderate, high (and extreme in Manitoba) – based on the output from their respective models.

Models are also constantly validated and fine-tuned for the region where it is relevant. The model that is best for the Fusarium population and conditions in individual provinces in western Canada, or even across the border in the USA, might not be the same. However, crop scientists and pathologists continue to work together to determine how FHB risk maps can be most valuable to all farmers, including those along the border! Producers along the border may have a potential advantage in assessing risk, by using both maps and interpreting which one is most relevant for their farm. And keep in mind risk maps may not perfectly represent a producer’s individual field(s).

Regardless of the model used, no FHB risk map can be taken as a stand-alone tool to make management decisions about FHB as it only takes into account environment. The existence of disease requires 3 factors: the interaction of a susceptible host, a virulent pathogen, and an environment favourable for disease development. So although a risk map in Saskatchewan or Manitoba may show High risk due to environment, disease risk may be low if the wheat crop is not at the proper stage for infection.

We strongly encourage referring to additional information and consultation with local extension specialists and agrologists to determine if fungicide applications are needed to suppress FHB in your area.

If you have any questions on the FHB Risk maps or FHB management, please contact Manitoba Agriculture or the Saskatchewan Ministry of Agriculture.

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Remember the DISEASE TRIANGLE when using MAFRD’s FHB Risk Maps

Previously published June 2, 2014, updated June 24, 2015

MAFRD is providing daily maps on the risk of Fusarium Head Blight (FHB) infection.  The maps are available daily on MAFRD’s website at http://www.gov.mb.ca/agriculture/crops/seasonal-reports/fusarium-head-blight-report.html. The risk map produced June 24th (see below) shows how the risk for the development of  fusarium head blight has increased over the past few days based on temperature and moisture.

2015-06-24-fhb

The changes over the past week signal to producers to continually scout their fields for local conditions as their crop progresses.  But remember the disease triangle – the existence of a disease requires three factors: the interaction of a susceptible host, a virulent pathogen, and an environment favorable for disease development. Therefore, although the most current risk map shows high risk levels due to environment in some areas of the province, disease is prevented if the winter/spring wheat is not at the proper stage for infection.

Submitted by:  Pam de Rocquigny, Provincial Cereal Crops Specialist, MAFRD

 

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2015 Fusarium Head Blight Risk Maps On-Line!

The Fusarium Head Blight Risk Map webpage will be available at http://www.gov.mb.ca/agriculture/crops/seasonal-reports/fusarium-head-blight-report.html
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This website will be updated daily Monday to Friday with the current risk maps.
Please refer to the risk maps to help decide risk to your crop, based on heading and flowering stage of your crops.  Remember the disease triangle – the existence of a disease requires three factors: the interaction of a susceptible host, a virulent pathogen, and an environment favorable for disease development. Therefore, although a risk map may show High to Extreme risk levels due to environment, disease risk may be low if the wheat crop is not at the proper stage for infection.
Depending on the weather, wheat can move through the following stages of development below in as little as five days to more than a week.  So if a fungicide for FHB suppression is planned, scout your fields daily to ensure proper timing.
Wheat Development Stages
Submitted by:  Pam de Rocquigny, Provincial Cereal Crops Specialist, MAFRD & Holly Derksen, Plant Crop Pathologist, MAFRD
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Winter Wheat Varieties Response to Fusarium Head Blight in 2014

In 2014, winter wheat was impacted by fusarium head blight impacting both yield and quality. The FHB Index in 2014, as measured by the annual FHB Winter Wheat Survey, was 11.6%, higher than the 10-year average of 3.4% (see CropChatter post for complete report on survey at  http://cropchatter.com/results-of-the-2014-fhb-winter-wheat-field-survey/).

High levels of infection were also recorded at the five Manitoba Crop Variety Evaluation Trials (MCVET).  This provided an opportunity to evaluate how winter wheat varieties being tested post-registration by MCVET respond to fusarium head blight under non-misted conditions (natural infection) by measuring severity in-field, and assessing harvested samples for fusarium damaged kernels (FDK) and deoxynivalenol (DON) accumulation.

Composite samples of ten registered winter wheat varieties were collected from the three replicates at five MCVET sites: Arborg, Beausejour, Carberry, Isabella and Winnipeg.  BioVision Seed Labs in Winnipeg, Manitoba conducted the analysis. The level of FDK (%) was measured as per the Official Grain Grading Guide of the Canadian Grain Commission. The accumulation of DON (ppm) was measured using the ELISA test method.

The variety Emerson, rated as Resistant (R), had lower levels of FDK and DON compared to the other varieties (see Figure 1) and consistently had lower visual symptoms or severity as expressed by the FHB Index (data not shown).  Some varieties rated as Susceptible (S) consistently showed higher FHB severity, FDK and DON levels across all sites. However, data also shows there is variability of performance within the five resistance categories of Resistant (R) to Susceptible (S).

Figure 1: Average Levels of Fusarium Damaged Kernel (FDK) and Deoxynivalenol (DON) by Variety at Five MCVET Sites in 2014

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To reduce the risk of fusarium head blight, producers should select varieties with improved resistance as the study indicates varieties with improved resistance generally had lower severity, FDK and DON levels. However, caution must be used with one year of data, as presented in this study. Using data derived over two or more growing seasons over multiple sites is always recommended to provide the best indicator of variety performance.

If interested in more information, please contact [email protected].

Submitted by:  Pam de Rocquigny, Provincial Cereal Crops Specialist

Special thanks to the Manitoba Crop Variety Evaluation Team (MCVET) for providing funding and in-kind support.

 

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Results of the 2014 FHB Spring Wheat Field Survey

Forty-seven spring wheat fields in Manitoba were surveyed by MAFRD staff to visually assess the incidence and severity of fusarium head blight (FHB).  Fusarium head blight in each field was assessed by sampling 100 plants when most crops were at the growth stage of ZGS 73 – 85. In each field, the percentage of infected spikes (disease incidence) and the mean spike proportion infected (SPI) were determined. The FHB Index (overall severity) was calculated as (% incidence x % SPI / 100).

RESULTS:

Symptoms of FHB were observed in 35 out of the 47 fields. The average % disease incidence was 5.9% (range 0 – 28.0%), SPI was 16.8% (range 0 – 55.0%) and the resulting average FHB Index was 1.0% (range 0 – 7.4%). Table 1 further illustrates the average FHB Index in the four regions of Central, Eastern/Interlake, Southwest and Northwest, and the number of fields surveyed per region.

2014 FHB Index in Spring Wheat by Agricultural Region

The 2014 FHB Index of 1.0% was lower than the 10-year (2003-2012) average of 2.9% (see Table 2) and similar to the previous few years. No survey was conducted in 2013 but levels were considered low.

Average FHB Index in Manitoba Spring Wheat (2003-2012)

Although favourable conditions for inoculum development and infection of the winter wheat crop existed in 2014, a transition to warmer, drier weather conditions when spring wheat was at anthesis, combined with foliar fungicide application in majority of fields surveyed (83%), likely contributed to the reduced FHB severity and little to no yield or quality loss in spring wheat.

Samples of infected heads were also collected and sent to AAFC Morden for further analysis of Fusarium species responsible for infection.

Submitted by:  Pam de Rocquigny, Provincial Cereal Crops Specialist

MAFRD Staff who conducted surveys: Ingrid Kristjanson, Dennis Lange, Earl Bargen, Derek Chomokovski, Rejean Picard, Amir Farooq, Lionel Kaskiw, Elmer Kaskiw, Marnie McCracken, Stephanie Jersak & Pam de Rocquigny.

A special THANK YOU to those producers who allow MAFRD to survey their winter wheat fields!

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Results of the 2014 FHB Winter Wheat Field Survey

Thirty-nine winter wheat fields in Manitoba were surveyed by MAFRD staff to visually assess the incidence and severity of fusarium head blight (FHB).

Fusarium head blight in each field was assessed by non-destructive sampling of 100 plants when most crops were at the growth stage of ZGS 73 – 85. In each field, the percentage of infected spikes (disease incidence) and the mean spike proportion infected (SPI) were determined. The FHB Index (overall severity) was calculated as (% incidence x % SPI / 100).

RESULTS:

Symptoms of FHB were observed in all 39 fields. The average % disease incidence was 32.9% (range 1.0 – 92.0%), SPI was 33.8% (range 9.1 – 93.1%) and the resulting average FHB Index was 11.6% (range 0.1 – 47.6%). Table 1 further illustrates the average FHB Index in the three regions of Central, Eastern/Interlake and Southwest, and the number of fields surveyed per region.

2014 FHB Index by Agricultural Region

The 2014 FHB Index of 11.6% was higher than the 10-year (2004-2013) average of 3.4% (see Table 2), and the third highest in the same time period.

Average FHB Index Rating 10 years

High levels of FHB symptoms were measured in 2014 due to a number of factors, including favourable conditions for inoculum development and subsequent infection of the crop, variable crop staging resulting in difficulty timing a fungicide application for suppression of FHB, and the large number of acres grown to varieties that are rated susceptible (S) to FHB.

Samples of infected heads were also collected and sent to AAFC for further analysis of Fusarium species responsible for infection.  Results will be available in the fall/early winter.

Submitted by:  Pam de Rocquigny, Provincial Cereal Crops Specialist

MAFRD Staff who conducted surveys: Ingrid Kristjanson, Dennis Lange, Earl Bargen, Derek Chomokovski, Rejean Picard, Amir Farooq, Lionel Kaskiw, Elmer Kaskiw, and Pam de Rocquigny.

A special THANK YOU to those producers who allow MAFRD to survey their winter wheat fields!

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Manitoba Insect & Disease Update – July 28 to August 1, 2014

A Manitoba Insect and Disease Update for the week of July 28-August 1, 2014 has been posted at: http://www.gov.mb.ca/agriculture/crops/seasonal-reports/insect-report-archive/insect-update-2014-08-01.html

Highlights include:

Pathology:

  • Fusarium head blight risk for wheat is moderate to low in different areas of Manitoba. Most of the wheat crops have finished flowering and thus at low risk. By end of the month, Fusarium head blight risk maps may not be needed.
Entomology:
  • Grasshoppers continue to be a concern in some fields.
  • Canola growers should be checking canola for Lygus bugs. Lygus can potentially be of concern when they feed on the pods of canola if levels are high, although feeding to flowering crops is not likely to be economical as canola has a very good ability to compensate for damage to flowers, especially when soil moisture is good. So far Lygus levels appear to be below economic levels in canola, with a few exceptions in the Eastern part of Manitoba.

Note: For those monitoring traps for bertha armyworm, the traps can be removed after you do your counts this week. We have enough weeks of data to know what the regional risks are. Overall trap counts in Manitoba were quite low this year. A map of the cumulative counts, as of July 28th, is posted in the update, and risk maps are also posted at the following MAFRD website (the July 28th map will be posted tomorrow): http://www.gov.mb.ca/agriculture/crops/insects/bertha-armyworm-forecast.html

Submitted by: John Gavloski, Entomologist & Vikram Bisht, Pathologist, MAFRD

Managing Fusarium Head Blight At Harvest

Winter wheat harvest 2014 will start shortly in Manitoba.  Field surveys being conducted by MAFRD staff are indicating higher than normal levels of fusarium head blight (FHB) in many winter wheat fields.

Unfortunately at this late stage of the growing season where harvest is right around the corner, there are no easy answers in managing FHB that is present. However, before harvest (and before a preharvest treatment is applied if one is planned), farmers and agronomists should head out to the fields for some final scouting to determine what, if any, harvest and storage strategies can be used to minimize the impact of fusarium damaged kernels. Careful harvesting, drying and storage strategies are the farmer’s best way to try and maximize grain quality and marketability.

The key at harvest is to try and prevent infected kernels from going into storage. Here are a few suggestions:

  • Thoroughly scout each field noting if there are any differences in infection levels between fields or if there are patterns within fields that are more affected by FHB, such as low areas or fungicide application misses.
  • Use higher fan speeds to try and blow infected kernels out the back. Research at Ridgetown found there was a tenfold decrease in Fusarium-damaged kernels in the grain sample when fan speeds were operated to deliver maximum air blast. However, the downside to this strategy is higher fan speeds can result in healthy kernels going out the back as well. And infected kernels blown out the back can provide a source of inoculum in future years.
  • Reduce combine travel speed as the slower speed allows for increased separation of the grain by allowing the increased air blast time to separate the good kernels from the infected kernels.
  • After harvest, gravity table grain separation may be effective in removing light-weight, damaged kernels. The increased marketability of the cleaned grain may pay for the cost of the clean-out process.

For additional information on harvest, drying and storage, as well as seed and feed considerations, visit MAFRD’s website at http://www.gov.mb.ca/agriculture/crops/plant-diseases/managing-fusarium-head-blight-harvest.html

Submitted by:  Pam de Rocquigny, Provincial Cereal Crops Specialist

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With FHB, Resistance does not equal immunity!

In fall of 2014, the first winter wheat variety to be rated Resistant (R) to Fusarium Head Blight (FHB) will be available to producers – a variety named Emerson.

However, it is imperative that farmers know that resistance or an R rating does not equal immunity. In fact, plants don’t have immune systems and therefore can’t be immune to any disease. Depending on the level of disease pressure, varieties that are rated as resistant will be infected to some degree. If disease pressure is high (i.e. high inoculum levels, conducive environmental conditions for a long period of time), yield loss due to FHB can still occur in R-rated varieties.

In Table 1, FHB reaction data collected in the cooperative registration system is provided illustrating how Emerson performed relative to other winter wheat check varieties and supplementary checks. Emerson showed a consistent improved reaction to FHB comparative to the resistant supplementary checks, hence the R rating. But as the table also illustrates, the R rating does not equal immunity as FHB was still measurable in each of the three years.

Table 1: Fusarium head blight (FHB) reaction of Emerson, the check cultivars and supplementary checks, Western Winter Wheat Cooperative Registration trials (2008-2010).

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z Visual rating index = % incidence x % severity / 100.
y Disease response category: R = resistant, MR = moderately resistant, I = intermediate, MS = moderately susceptible, S = susceptible.
x Supplementary checks were chosen to assist in the differentiation of resistance levels based on long term data collection.

Field surveys are being conducted in winter wheat and in the MCVET winter wheat trials to measure level of FHB infection.  To date, all fields and all varieties have symptoms of FHB in 2014.

Use Multiple Management Practices!

This is why it is still important to use more than one management practice. Extensive research over the past 20 years have shown that using multiple management options, including crop rotation, fungicide application, tillage, and variety selection, is the best way to mitigate the risk of FHB. But unfortunately, FHB infection will always be highly influenced by environment. Under high levels of the disease, all varieties will sustain damage.

Submitted by: Pam de Rocquigny, Provincial Cereal Crops Specialist, Manitoba Agriculture

Source:  Graf, R. J., Beres, B. L., Laroche, A., Gaudet, D. A., Eudes, F., Pandeya, R. S., Badea, A. and Randhawa, H. S. 2013. Emerson hard red winter wheat. Can. J. Plant Sci. 93: 741-748.
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