Assessing Sclerotinia Risk in Canola

Early May 2014 seeded canola is now flowering, and later May seeded crops are not too far behind. With the widespread rainfall in Manitoba over the Canada Day weekend, soils are moist to saturated and temperatures are favorable for sclerotinia infection and development.

MAFRI currently does not produce sclerotinia risk maps like we do for Fusarium Head Blight, as we do not have a proven and consistent model to forecast sclerotinia risk.   Alternatively, there is a newly posted risk assessment calculator for sclerotinia spray decisions and economic imapct available at http://www.gov.mb.ca/agriculture/business-and-economics/financial-management/farm-software-and-worksheets.html

We have the inoculum as we grow multiple sclerotinia susceptible crop (canola, soybean, sunflower, dry bean, etc.), but risk and disease development is dependent on a combination of inoculum as well as day/night temperature, precipitation, crop canopy and soil moisture.

 Scout and monitor your fields, disease development risk increases (and need for fungicide) if you have the following conditions:

  • Ground is damp to wet and,
  • Canopy is moderately closed to closed (i.e. you cannot see the ground through the leaves), and
  • Canopy is still damp to wet when walking through the field at 10am (i.e. your pants are wet), and
  • Field is at 20 – 50% flowering 

 

Flowers open  = % flowering?

Find the main stem on the canola plant to assess flowering

  • 10% flowering = 10 open flowers 
  • 20% flowering = 14-16 open flowers 
  • 30% flowering = 20 open flowers, some small pods 
  • 50% flowering = >20 open flowers, small pods and a few well formed

Conditions can change throughout flowering.  If the canopy is wet now at 6 leaf stage, but your plant stand is thinner and the canopy is open and dry at 20% flower you may not feel that you need to spray, but if you are at 10% flowering now, the canopy is thick and the ground is wet, you may want spray.

The MAFRD Guide to Field Protection for Disease Control can be found at http://www.gov.mb.ca/agriculture/crops/weeds/guide-to-crop-protection.html

 Prepared by:  Anastasia Kubinec – MAFRI Oilseed Crop Specialist  

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Manitoba Sclerotinia Risk Assessment Update

MAFRI currently does not produce sclerotinia risk maps like we do for Fusarium Head Blight, as we do not have a proven and consistent model to forecast sclerotinia risk. 

Since Manitoba producers grow multiple sclerotinia susceptible crop (canola, soybean, sunflower, dry bean, etc.), the inoculum is present in the environment, but risk and disease development is dependent on a combination of inoculum as well as day/night temperature, precipitation, crop canopy and soil moisture, which can vary from field to field.

 Scout and monitor your fields, you may be at greater risk and require a fungicide application if you have the following conditions:

 Canola:

  • Ground is damp to wet and,
  • Canopy is moderately closed to closed (i.e. you cannot see the ground through the leaves), and
  • Canopy is still damp to wet when walking through the field at 10am (i.e. your pants are wet), and
  • Field is at 20 – 50% flowering (you are wanting to cover the petal so when it falls into a humid canopy, it won’t be a viable food source for the sclerotinia to start on).

 Conditions can change throughout flowering.  If the canopy is somewhat open and dry at 20% flower you may not feel that you need to spray, but if there is a rainfall event and the canopy is wet at 30 – 40% flower, you may want spray then.

 Dry Bean:

  • Ground is damp to wet and,
  • Canopy is moderately closed and is continuing to close, and
  • 50 – 80% of the Field has started to flower (at least one open flower per plant)
  • Dry bean may require a second application at full flower, depending on the precipitation, temperature and canopy moisture

 Sunflower (for Sclerotinia Head Rot only) :

  • Ground has been damp to wet for the past week, and
  • Plants are at R5 (sunflower face is open with ray petals out, but pollination has not yet started)

Spraying for sclerotinia in soybean is not being considered at this time as flowering has not yet occurred. Damage and economic loss in soybean has only occured in one growing season on record. Sclerotinia development can occur under extreme wet and cool conditions, or the crop is significantly lodged and further information will be posted if these conditions do occur later on in the 2013 growing season. 

Canola Council of Canada July 3, 2013 New Release – Moisture Raises Sclerotinia Stem Rot Risk  http://canolacouncil.org/news/moisture-raises-sclerotinia-stem-rot-risk/                                                    

NSDU Sclerotinia Risk Map http://www.ag.ndsu.edu/sclerotinia/.  Please note this is based on temperature and precipitation only and is not based on individual field conditions

 

Prepared by:  Anastasia Kubinec – MAFRI Oilseed Crop Specialist  and  Holly Derksen – MAFRI Field Crop Pathologist

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