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The Cropwalker - Ontario Crop Progress Update v2

This is a special edition based on Twitter polls and the individual conversations of Matt Pot of Grain Perspectives -www.grainperspectives.com and The Cropwalker Newsletter team.

Thank you to Bayer CropScience for sponsoring our work.


This is a crop progress update based upon an August 6th, 2019 Twitter roll call. Similar to the last survey, we surveyed the percentage of Ontario corn acres that have tasseled. At this point in the growing season, the questions that start to arise are; Which areas are behind in tasseling relative to norm? And, when will we get frost?

Days from tasseling to black layer

It takes about 55-65 days from silk to maturity. (there are differences among hybrids) If corn silks appeared on July 25, your crop needs to be frost-free until roughly September 25-October 5 to reach physiological maturity. If a frost hits before then, it will force a black layer (or brown layer). If in that case the corn is close to maturity, the effects on quality and yield will be minimal. (from The Cropwalker, Volume 2, Issue 30)

Luckily OMAFRA does have data on average frost free periods within Ontario. See below.

Figure 1 - Climate Zone Map of Ontario (1976-2005)
Table 1 - Average Frost (0 C) Dates by Climatic Zone in Ontario

Understanding the table; Dates listed are the average of the first date frost at 0C from 1976 to 2005. There is a 10% risk of frost 14 days prior to the date listed, 25% 7 days prior to date listed, and 50% at the date listed. The first frost at -2C usually occurs 2 weeks later than the date listed in the table.

For example; If you farm in Lambton County, there is a 10% risk of frost on September 29th, 25% risk of frost on October 6th and 50% risk of frost on October 13th. A -2C frost on average would occur on October 27th.

Source: http://www.omafra.gov.on.ca/english/crops/facts/climzoneveg.htm (Map Source: Weather Innovations Incorporated)

August 6th, 2019 Twitter Survey Response – What percentage of your corn is tasseled?

July 28th, 2019 Twitter Survey Response – What percentage of your corn is tasseled?

June 23rd, 2019 Twitter Survey Responses – In 2019, you planted X% of your 2018 corn acres?