Scouting & Management of Sunflower Rust

Rust in sunflower is caused by the fungus Puccinia helianthi, which overwinters on plant stubble and produces five spore‐stages throughout the year. Early in the season, orange rust pustules appear on the upper surfaces of cotyledons of seedlings and volunteer plants, with later infections moving to the underside of the leaf (Figure 1).  The most yield-damaging stage occurs in late July to early August, when symptoms of infection show up as dusty, dark brown pustules on leaf surfaces, petioles and flower bracts (Figure 2). As the disease develops, black teliospores form, overwintering on the crop residue.

 

Figure 1: rust on leaf underside (photo: MB Ag)

 

Figure 2: Rust on leaves, stem. Wilting plants (photo: MB Ag)

Sunflower rust becomes a more severe issue in later-planted crops, or crops with weaker genetic resistance. Warm, moist weather favours rapid multiplication of rust spores, and windblown spores can travel quickly from field to field.  Early stages of sunflower rust in 2018 have been observed in the Cypress River area the week of July 3rd.

High plant populations and dense, leafy canopies allow humid conditions to remain in the crop throughout the day, compounding injury from rust spores.

Scout sunflower fields regularly to monitor the development and stage of rust infection. Watch for dense clusters of brown, powdery pustules scattered over all plant surfaces.  Orange-brown ‘dust’ on clothing after being in a sunflower field is a key indicator that rust is present, and more careful scouting is needed. Withered lower leaves are an indication that the surface is heavily infected.

Controlling rust after infection is primarily done using triazole-based and strobilurin-based fungicides. Recommended action in rust-infected crops is to use a fungicide from the triazole group after the first onset of symptoms, at the 2-3% pustule coverage on the upper four leaves at flowering (R5).  Strobilurin-based fungicides act more as a ‘protectant’, applied earlier before widespread infection occurs.

See more information on sunflower rust at https://www.gov.mb.ca/agriculture/crops/guides-and-publications/#gfcp

See Guide to Field Crop Protection for more information on fungicides registered at https://www.gov.mb.ca/agriculture/crops/guides-and-publications/#gfcp

National Sunflower Association of Canada information on Sunflower Diseases: http://www.canadasunflower.com/wp-content/uploads/2012/11/Disease.pdf

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What Would an Early September Frost Do to My Sunflowers?

September 5, 2017 – Risk of Frost in Pinawa, Winnipeg, Whiteshell and Steinbach tonight……….

Frost anytime before the sunflower crop reaches physiological maturity (R9) can cause damage. Once sunflowers reaches the R7 stage (ray petals have dropped, back of head starting to turn yellow), sunflower can withstand temperatures as low as -4° C, but temperature, duration and crop stage will influence the type and amount of damage.

A killing frost in sunflowers is considered to be -4 to -5° C for 6 or more hours, as this low temperature for the extended period is required to penetrate the thick layer in the back of the sunflower head and start the dry down process.  See attached bulletin for more details:

http://www.gov.mb.ca/agriculture/crops/production/pubs/frost-sunflowers.pdf

Visit www.canadasunflower.com for more updates on all sunflower issues

Visit Manitoba Agriculture http://www.gov.mb.ca/agriculture/crops/ for more frost information for other crop types

Submitted by Anastasia Kubinec, Manager – Crop Industry Development, Manitoba Agriculture

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When Should I Desiccate My Sunflowers?

The ‘right’ time to desiccate sunflowers is when the back of the head looks banana yellow and the bracts are brown up to and past the shoulders.  This visual combination equates to R9 or typically around 30% seed moisture.  You want to visually check out different parts of your fields, looking at the areas that you know advance faster and the ones that advance the slowest.  Try to aim that the majority of you field is at the R9 stage.

 

IMG_20150901_194531

Reasons to desiccate would be that even though seed moisture is drying down, to properly thresh out the seeds, the head material and stalk material need to be dry as well.  Desiccation speeds up time to harvest meaning seeds are off the field faster, which can mean less losses from head rot damage, stalk breakage and bird feeding.  National Sunflower Association of Canada has just released a bulletin explaining more on timing and products at http://www.canadasunflower.com/

Not so sure on the visual description?  You can hand shell out a couple of heads and test the seed moisture to see if the seed is around 30% moisture or less.  An easy method is the microwave method, which is explained in this paper http://library.ndsu.edu/repository/bitstream/handle/10365/6109/farm_45_02_03.pdf?sequence=1

 

Submitted by: Anastasia Kubinec, MAFRD Oilseed Crop Specialist

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Should I Spray my Sunflowers for Sclerotinia Headrot?

Sclerotinia in sunflowers can be frustrating and devastating, especially in the form of headrot. Headrot is very weather related. It needs rainfall to wet soils stimulate sclerotia to produce apothecia mushrooms and ascopores. Ascospores once on disk petals, need prolonged wetness to allow the infection and growth of the fungus on the petals and spread into the sunflower head tissue.

It takes approximately 14 days after a “ground soaking” rainfall for the mushrooms to appear and produce ascospores.  In 2016, most areas in Manitoba have saturated soils, making an ideal environment for apothecia emergence, which could be the start of the lifecycle to cause sclerotinia head rot in sunflowers.

Weather data can be used in combination with a risk calculator to determine if a fungicide is needed.  You can find the Manitoba Agriculture calculator here http://www.gov.mb.ca/agriculture/business-and-economics/financial-management/pubs/calculator_sclerotiniadecisiontool_sunflowers.xls

It has only been in the past couple of years that sunflower growers have had fungicide registered to control headrot.  With limited use of use, control has been not always been what was expected.  The fungicides available are protectant and work to protect plant when disease infection potential present.  If there was infection prior to application, or, if pressure remains high after application, control may be less than expected.

National Sunflower Association of Canada has put out a bulletin talking about sclerotinia headrot control in sunflowers in 2015 and can be found at http://www.canadasunflower.com/wp-content/uploads/2015/07/Sunflowers-sclerotinia-and-fungicides.pdf

 

Submitted by: Anastasia Kubinec, Manitoba Agriculture, Oilseed Crop Specialist

 

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Yields Respectable in 2014 Despite a Challenging Year

Manitoba Agricultural Services Corporation (MASC) has released an early version of the 2014 yield report with 99.8% of the Harvest Production Reports (HPRs) keyed in.  The table below summarizes the 2014 average yield by crop type based on the harvested acres, as well as comparisons to 2013 and a 5-year average (2009 to 2013).

2014 yields

In February 2015, MASC will release their annual Yield Manitoba publication and update their Manitoba Management Plus Program (MMPP) website (http://www.mmpp.com/mmpp.nsf/mmpp_index.html) where further information on yields and acres by variety will be released.  Additionally, the data will be more complete in February as all HPR’s will be keyed in.

Submitted by:  Pam de Rocquigny, Anastasia Kubinec & Dennis Lange, Crop Specialist with MAFRD

Special Thanks to Doug Wilcox, MASC, for providing the 2014 data!

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Harvest Hints for Combining Sunflowers

As the first seeded sunflowers are desiccated and are drying down, here are some helpful hints on combining from the National Sunflower Association of Canada (NSAC). 

Harvest 2014 – Special Bulletin

Sunflowers can be safely combined when the seed moisture is below 18-20%. However, allowing sunflowers to dry-down to a moisture content of 9.5 -12% reduces the need for drying on-farm.  At 12% moisture content, seed can be stored in bins with aeration. Any moisture content over 12% will require drying to avoid spoilage. Oil-type sunflowers can be dried with temperatures of 71º to 104º C (160ºF to 220ºF) but confection-type sunflower seed may scorch or wrinkle with these temperatures. Sunflower seed should be cooled before storage, since even sunflowers at 8.5% moisture can spoil if stored when warm.

For more information on sunflowers:

National Sunflower Association of Canada –  www.canadasunflower.com

MAFRD Sunflower Production and Management – http://www.gov.mb.ca/agriculture/crops/production/sunflowers.html

 

Information Contributed by Anastasia Kubinec, MAFRD Oilseed Crop Specialist

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Early September Frost Impact on Sunflowers

Frost anytime before the sunflower crop reaches physiological maturity (R9) can cause damage. Once sunflowers reaches the R7 stage (ray petals have dropped, back of head starting to turn yellow), sunflower can withstand temperatures as low as -4° C, but temperature, duration and crop stage will influence the type and amount of damage.

A killing frost in sunflowers is considered to be -4 to -5° C for 6 or more hours, as this low temperature for the extended period is required to penetrate the thick layer in the back of the sunflower head and start the dry down process.  See attached bulletin for more details

2014 Sept Frost and Sunflowers

Visit www.canadasunflower.com for more updates on all sunflower issues

Visit MAFRD http://www.gov.mb.ca/agriculture/crops/ for more frost information for other crop types

submitted by Anastasia Kubinec, MAFRD Oilseed Crop Specialist

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Sunflower Staging and Guessing Maturity

SF G&D chart

Prepared by Anastasia Kubinec, MAFRD Oilseed Crop Specialist

Sunflower planting was spread out in 2014, which means flowering and dry-down will be as well. The chart below gives and indication to the amount of time it will take the crop to reach R8 to R9. This is a guide only. Sunflower development and dry down is based on temperature. If August is all above 25C during the day and doesn’t go below 10C at night, the sunflower crop will develop much faster than this!

From August 5th to 31st, regardless of location, there is typically 275-320 Sunflower GDD accumulated in Manitoba. To get from R5.1 to R9 the crop needs 393 GDD.

Sunflower Stage Sunflower GDD (Celcius)
VE 97
V1 117
V12 333
R1 569
R2 647
R3 726
R4 805
R5.1 883
R5.5 962
R6 1040
R7 1119
R8 1197
R9 1276

 

*Sunflower GDD= (Tmax+Tmin)/2 – 6.7C

   Example            = ((25+10)/2)-6.7=10.8

For more information, contact NSAC agronomist at (204)750-2555 or MAFRD Oilseed Crop Specialist at (204) 750-2717

 

References

Standardized Growth Stages described by Schneiter and Miller. 1981. Description of Sunflower Growth Stages. Crop Science 11: 635-638

Graph Developed by MAFRD Crops Knowledge Centre

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When is the Best Time to Spray Sunflowers for Head Rot?

With the registration of fungicides for sclertotinia head rot control in sunflowers, growers have an excellent management tool for reducing the impact of an economically devastating disease.

As the products and use is new to many growers, there are a number of question on timing.

  • Sunflower staging : Target the R5.1 to R5.2 stage (10-20% disk flowers open)
  • Field staging: 50-80% of heads at R5.1 to R5.2
  • Number of applications: Depends of product. If registered and conditions good for infection a second application can be made 12-14 days after the first application

 

Expert advice from Dr. Khalid Rashid, Pathologist with AAFC Morden, who has tested the head rot fungicides and sunflower staging timing for over 10 years is that:

“The growth stage of R5.1-R5.2, until end of flowering( 3 weeks window) is the most susceptible stage.  The main factors for susceptibility are the availability of ascospores from mushroom production in adjacent fields (less are produced in the sunflower fields), and there is humidity in the air and on the sunflower heads, for ascospores to germinate and infect the heads.    Sometimes, a second application 2 weeks after the first application may further reduce the disease infections.   In some years/some fields get high late infection after the end of flowering due to a flux of ascospores production late in the season coupled with favourable humidity/rain conditions.”

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Manitoba Insect & Disease Update – Week of July 14th to 18th

A Manitoba Insect and Disease Update for the week of July 14-18, 2014 has been posted at: http://www.gov.mb.ca/agriculture/crops/seasonal-reports/insect-report-archive/insect-update-2014-07-16.html

Highlights include:

  • Flowering canola crop needs to be protected against white mold since there have been many rain events lately.
  • Phytophthora root rot of soybean has started showing up, especially in flooded fields.
  • Early lesions of sunflower rust have been found in a 2nd location.
  • Alfalfa weevil levels were quite noticeable in some alfalfa fields, but they are now starting to pupate, so levels are declining.

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

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