Hot days (28-30°C and up) and warm nights (16°C and up) from bud to mid-flowering stages can have a significant effect on canola yield.
Cool nights offer some recovery from hot days. Warm nights do not provide a recovery period, and more flowers are aborted, producing blanks along the stem. Even with a few days of heat, it can take a week for hormone balance and regular pod formation to return. Recently opened flowers with shortened stamens that don’t protrude above the petals can be a sign of heat damage. With the current heat spell, when checking canola fields for sclerotinia timing, you could also look for heat damaged flowers.
![](https://www.canolacouncil.org/wp-content/uploads/2020/10/Heat-effect-on-flower-clusters.png)
When heatwaves and flowering coincide, boron is often touted as a remedy, but this touting rarely, if ever, comes from people who’ve done or read the research. When Alberta Agriculture oilseed specialist Murray Hartman ran his meta-analysis of boron studies, results showed no relationship between boron response and temperature. In short, analysis showed no boron response – even when temperatures were hot at flowering.
The Canola Council of Canada boron trials as part of the Ultimate Canola Challenge in 2013-15 found no consistent yield benefit from boron treatment, including in those plots with very high yield results. Read results.
Low cost does not justify boron. Farmers hear of many $5/ac treatments that fall into the low risk/low reward category. They become high risk/low reward if growers start to apply numerous “low cost” treatments per year. If growers want to test boron or any of these other treatments for themselves, try a few test strips (testing one treatment at a time). Put test strips in uniform parts of the field and follow protocols.
Further reading:
Murray Hartman Agronomy Update presentation
Ontario boron study report