When to Swath After Frost

Sep 05, 2011

When to Swath After Frost

In the past few days some regions, particularly in central Alberta, have experienced some light frosts. Producers are asking if these frosts caused damage and whether they should be swathing right away or waiting to let the crop mature further. Below are some things to consider when making this decision, followed by a link to a fact sheet with more details on assessing standing fields following fall frost.  

Scout, don’t swath. Given that in most affected regions temperatures did not dip below minus 2 C, damage is likely to be minor meaning swathing prematurely may do more harm than good. However, it is important to get out there and check crops to ensure damage is not greater than expected. If plants are severely damaged the pods will often take on a white, wilted appearance. This is a sign that pods are desiccating which will quickly lead to pod shatter and pod drop, especially with warm sunny afternoons. If pods are desiccating rapidly, swathing right away will preserve as much yield as possible.

If pods do not appear to be severely damaged, then continue monitoring rather than swathing right away. You may see some speckling on the stem and pods, but much of the seed inside will continue to mature as long as the plant is still alive. If no wilting, leave the crop standing and check daily.  

What to look with daily monitoring:
—If the majority of the seeds remain turgid, delay swathing to allow for further seed maturity. Swathing assessment will be similar to an undamaged crop, but focus on the healthy seeds to monitor for firmness and seed color change. 
—If the pods begin to desiccate, swath during periods of dew or high humidity to reduce the amount of pod shelling and pod drop.  

Why wait? The amount of frost damage depends on various factors including crop stage, degree and length of frost, relative humidity, and presence of rain or dew. In many cases, a light frost will damage the outside of pods but seeds can continue to mature — increasing yield and quality — if the crop is left standing.  Click here for more information on assessing crops following fall frost.

Source: Canola Council of Canada

Video: Spring 2026 weather outlook for Wisconsin; What an early-arriving El Niño could mean

Northeast Wisconsin is a small corner of the world, but our weather is still affected by what happens across the globe.

That includes in the equatorial Pacific, where changes between El Niño and La Niña play a role in the weather here -- and boy, have there been some abrupt changes as of late.

El Niño and La Niña are the two phases of what is collectively known as the El Niño Southern Oscillation, or ENSO for short. These are the swings back and forth from unusually warm to unusually cold sea surface temperatures in the Pacific Ocean along the equator.

Since this past September, we have been in a weak La Niña, which means water temperatures near the Eastern Pacific equator have been cooler than usual. That's where we're at right now.

Even last fall, the long-term outlook suggested a return to neutral conditions by spring and potentially El Niño conditions by summer.

But there are some signs this may be happening faster than usual, which could accelerate the onset of El Niño.

Over the last few weeks, unusually strong bursts of westerly winds farther west in the Pacific -- where sea surface temperatures are warmer than average -- have been observed. There is a chance that this could accelerate the warming of those eastern Pacific waters and potentially push us into El Niño sooner than usual.

If we do enter El Nino by spring -- which we'll define as the period of March, April and May -- there are some long-term correlations with our weather here in Northeast Wisconsin.

Looking at a map of anomalously warm weather, most of the upper Great Lakes doesn't show a strong correlation, but in general, the northern tiers of the United States do tend to lean to that direction.

The stronger correlation is with precipitation. El Niño conditions in spring have historically come with a higher risk of very dry weather over that time frame, so this will definitely be a transition we'll have to watch closely as we move out of winter.