Early September Frost – What is Going to Happen to My Soybeans?

September 5, 2017  – Pinawa, Winnipeg, Whiteshell and Steinbach overnight forecasts, Environment Canada is stating there is a risk of frost. 

Whether or not there is yield loss in soybeans depends on two factors.  One is how cold it gets and how hard it freezes.  We won’t know the story on that until tomorrow.  The other factor is the growth stage the soybeans are at and that is determined by examining the pods on the plant.  It is all about the pods, so don’t get distracted by the condition of the leaves.  The more advanced/mature the soybeans pods are, the less the potential yield loss.

Manitoba Pulse and Soybean Growers has a maturity guide on their website that will provide you with excellent pictures and descriptions of the growth stages we are now seeing in our fields.  Use it as your guide in determining where your beans are at.  Click on the link below to access:

http://www.manitobapulse.ca/wp-content/uploads/2015/08/Soybean-MATURITY-GUIDE_Apr-2017_WR.pdf

In terms of yield loss, use the following as a guide:

  •  Frost during the R5 stage can reduce yield by 50%-70%.
  •  Frost at the R6 stage can reduce yield by 20%-30%.
  •  Frost at the R7 stage can reduce yield by only about 5%.
  •  At the R8 stage no yield reductions are expected. Dupont Pioneer has also put together a factsheet on frost damaged soybeans that is helpful  https://www.pioneer.com/home/site/us/agronomy/library/frost-damaged-soybeans/.

You will always find some variation around predictions of yield losses due to frost in soybeans.  This is to be expected.  There is no absolutely right answer.  No crop is uniformly at one growth stage and every frost event is unique in how it plays out.  The information above is merely meant to serve as a guide.

Let’s hope we stay well above zero!!

Submitted by: Terry Buss, Beausejour Farm Production Extension Specialist – Crops, MB Ag and Dennis Lange, Pulse Crop Specialist, MB Ag.

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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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Are Herbicides Still Effective After a Fall Frost?

Fall is a great time to control perennials such as Canada thistle, perennial sow thistle and dandelion. As temperatures cool, nutrients move from the leaves down into the roots and if a herbicide can be taken up and translocated with those nutrients, it can equal better control. Glyphosate and/or the group 4s are examples of herbicides that provide effective fall control of perennials.

A frost event though, can kill some weeds or can damage leaf tissue which will reduce herbicide uptake and reduce the level of weed control. Within the next few days after the frost, you need to assess the target weeds in the areas that you want to obtain control – are the weeds still growing?  How much leaf tissue has been damaged?

Light frost: A light frost (0 to -3°C) can actually improve weed control by increasing herbicide translocation to the root.  However, duration of the frost also plays a role.  Check your weeds for frost damage if you plan on a herbicide application after a light frost.  Herbicides can only be taken up and translocated by weeds that are healthy and actively growing.

If you do spray – spray in the afternoon when temperatures are warm and sunny, as this will help with herbicide uptake.   You’re looking for daytime temperatures of ~8 to 10°C for at least 2 hours. Use rates appropriate to the stage and time of year – fall applications of glyphosate are recommended at a higher rate than when controlling weeds pre-harvest.

Hard frost: Depending on the damage, a hard frost (≤ -5°C) can put an end to (effective) post-harvest weed control. However, if the plant leaves are still shiny green with minimal leaf tissue damage (i.e. not blackened/brown or brittle) or if less than 40% of the plant has more serious leaf tissue damage (i.e. blackened/brown or brittle) there may still be a window to make a herbicide application. Wait at least 48 hours before assessing frost damage after a hard frost.

If you do spray – read the ‘If you spray’ paragraph above, it still applies.  You need those daytime temperatures to hit ~8 to 10°C for at least 2 hours. In addition, consider your coverage – higher water volumes may improve uptake in more heavily damaged weeds.

One last thing – look at the forecast for the next week following the application.  If daytime temperatures are below 8°C and/or if night-time temperatures are forecasted to continually be below freezing, it may be too late to make the application to get the economic control you are looking for.

Submitted by: Jeanette Gaultier, Provincial Weed Specialist, Manitoba Agriculture

Visit Manitoba Agriculture Crops webpage for more current topics: www.gov.mb.ca/agriculture/crops/seasonal-reports/current-crop-topics.html#agronomy; or the Manitoba Agriculture Weeds webpage for more information on fall control of dandelion and quackgrass: www.gov.mb.ca/agriculture/crops/weeds/.

 

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ANNUAL OR WINTER ANNUAL?

Fall is the most effective time to manage certain weed species. The recommendations seem clear-cut:  winter annuals = fall herbicide application/tillage; annuals = no fall management.  But figuring out the life cycle of the weeds in your field this fall is the catch……

Bromes, cleavers, chickweed, night-flowering catchfly, narrow-leaved hawk’s-beard, shepherd’s-purse and stinkweed are all facultative winter annuals, meaning that they can germinate in either the fall or the spring depending on environmental conditions.  These weeds are often best managed in the fall, if populations warrant it.  In general, waiting until about this time of year maximizes fall-germinating flushes of winter annuals.  If using a herbicide, consider weed stage and the weather forecast, prior to application.

The problem is, given the right conditions – like the long falls and mild winters we’ve had the last few years –several of our annual weed species can also successfully overwinter:

Biennial wormwood – Despite its name, biennial wormwood behaves like an annual in agricultural fields.  When scouting, estimate the average growth stage of biennial wormwood populations in a field.  If the majority of the plants have already set seed, a fall herbicide application won’t help.  An application may be worthwhile only if there is a large flush of biennial wormwood that haven’t set seed and are less than ~3 inches tall.  Herbicide tank-mixes containing glyphosate + group 4 are more effective than glyphosate + group 2 on this weed.

Round-leaved mallow (RLM) – This annual weed can act as either a winter annual or a short-lived perennial, although it is more sensitive to freezing than our common winter annuals.  Mild winters in 2015 & 2016 provided the right conditions for RLM to overwinter, allowing it to become (even more) problematic in certain fields over the last few growing seasons.  Long range forecasters are predicting a harsh winter across the prairies this year, which should control RLM.  However, if you have little faith in forecasts and decide to apply a herbicide, glyphosate mixed with either Distinct or DyVel DSp has activity on this weed.

IMG_20150915_081215

Round-leaved mallow post-harvest


Stork’s bill –
Like biennial wormwood, stork’s bill tends to be predominantly an annual in Manitoba.  If this is a problem weed for you, scout affected fields to determine average weed stage.  Again, if most of your stork’s bill has set seed you’re better off working on a plan for next year.  Stork’s bill, especially larger plants, is relatively tolerant of many herbicides.  If you decide to apply a herbicide because of stork’s bill this fall, glyphosate + group 2 or glyphosate + group 2 + group 4 on weeds up to the 4 to 6 leaf stage is probably your best bet.

Submitted by: Jeanette Gaultier, Provincial Weed Specialist, Manitoba Agriculture

Information on more weeds and their life cycles is available at: www.gov.mb.ca/agriculture/crops/weeds/
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Minimum Air Temperatures – September 13/14, 2016

From Manitoba Agriculture’s AgWeather Program, a map showing minimum air temperatures reached September 13/14:

Picture1

In addition, the Crop Weather Report is a weekly summary of temperature (max., min., avg) and total rainfall along with seasonal accumulations of degree days, corn heat units and rainfall (actuals and % of normal) are provided for about 50 locations in the five regions.

Following are links to weather maps in pdf format for the time period of May 1st to September 11th:

The above maps will be updated every Monday during the growing season. They are available on the Manitoba Agriculture weather web site at http://www.gov.mb.ca/agriculture/weather/index.html .

For more information or to subscribe to the weekly Crop and Weather reports send your request to [email protected].

Follow Manitoba Agriculture on Twitter at @MBGovAg to get these seasonal reports and more.

 

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It’s That Time of Year – Talking Fall Frosts in Manitoba

UPDATED FROM ARCHIVED CROP CHATTER POST MADE AUGUST 15, 2013

As we enter in the later parts of the growing season, fall frost enters the minds of most people involved in the grain industry.  As everyone knows, frost can have an impact on a crop’s quality and yield.  There were a few areas reporting a light frost event the morning of September 14th.

The extent of frost damage to a crop will depend on several factors. The species, stage, and hardening of the crop, the soil type and soil moisture, the actual air temperature, the duration of freezing, and the rapidity with which freezing takes place are all important. A drop in air temperature of short duration will cause less damage than a prolonged periodthe same low temperature. When the air temperature drops to 0°C, cereal and other crops may not sustain damage. Rather, damage or total loss is more common when minimum temperatures drop below -2°C, often referred to as a killing frost.

Given its sporadic nature, long-range forecasting of frost is nearly impossible. Rather, the climate record of an area is used to determine probable dates of frost based on long-term temperature records. While this will not provide an actual frost date in a particular year, it will present the likelihood that frost may occur on a certain date. This can be a valuable planning tool.

The Manitoba Ag-Weather Program released updated FIRST FALL FROST MAPS in 2014 which are made from the new township gridded normal from a wider dataset of 1950-2010:

For additional information, please visit Manitoba Agriculture’s AgWeather Program at http://www.gov.mb.ca/agriculture/weather/agricultural-climate-of-mb.html.

Submitted by:  Pam de  Rocquigny, Provincial Cereal Crops Specialist, Manitoba Agriculture

Manitoba Agriculture on Twitter: @MBGovAg
Manitoba Agriculture on YouTube: www.youtube.com/ManitobaAgriculture
Manitoba Agriculture website: www.manitoba.ca/agriculture

 

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Frost Prior to Physiological Maturity in Corn

When frost occurs in the early fall before corn has reached physiological maturity (black layer), there is always concern about impact to yields and quality. The stage of crop, minimum temperature reached, relative humidity and duration of cool temperatures all contribute to the impact frost will have on the crop. Generally speaking, a light frost is considered below 0 but above -2°C, where a heavy frost is -2°C and greater.

In corn, grain yield and quality losses become less of a concern the closer the corn is to physiological maturity.

At R5, or the dent stage, crop impacted by either a light or heavy frost will be harvestable but there will be an impact to yield and quality (see Table 1). Within R5, kernels are often staged according to the progression of the milk line, i.e. ¼, ½, ¾. At ½ milk line (R5.5), moisture content of kernels is 35-40% and days to maturity is approximately 13-18 days away.

The stage R6, or physiological maturity, is reached when the milk line disappears and the starch line has reached the base of the kernel. Kernels have reached maximum dry matter accumulation and kernel moisture can range between 30 to 35% (but does vary by hybrid and environment). The formation of the black layer serves as a visual cue that the plant is mature.  At this stage, frost will have minimal impact to yield or quality.

Table 1: Relationship between corn growth stages and calendar days to maturity, yield loss, and other kernel characteristics

Days to Maturity Grain Corn

Source: NDSU Crop & Pest Report – August 8, 2013

A killing frost (-2°C) any time prior to physiological maturity (R6) will kill the entire plant which will stop kernel development. However, if the frost is not a killing frost and the leaves/stalks and husks are still green afterwards, grain filling will continue until maturity.

Picture2

Frost symptoms are water soaked leaves that eventually turn brown. Because it is difficult to distinguish living from dead tissue immediately after a frost event, the assessment should be delayed for a few days after a frost. (Photo by P. de Rocquigny)

Even though the leaves may be impacted, the plants will continue to scavenge nutrients from the remaining plant material to help complete growth and maturity.  However, the crop will still need the necessary heat units to aid in maturity.  If the necessary heat units aren’t received, a premature black layer may form, ending further grain fill, potentially impacting yield but more likely quality.

Submitted by: Pam de Rocquigny, Provincial Cereal Crops Specialist, Manitoba Agriculture

Manitoba Agriculture on Twitter: @MBGovAg
Manitoba Agriculture on YouTube: www.youtube.com/ManitobaAgriculture
Manitoba Agriculture website: www.manitoba.ca/agriculture

 

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Minimum Temperatures Reached September 12th

A PRELIMINARY map was created using data from MAFRD’s Ag-Weather Program that shows the Minimum Temperatures reached on September 12th.

Tmin20140912

More frost events were recorded Monday, September 15th.

More detailed weather information and the potential impact to crops will be available in Issue #20 of the Manitoba Crop Report at:  http://www.gov.mb.ca/agriculture/crops/seasonal-reports/crop-report-archive/index.html

More information on the Manitoba Ag-Weather Program can be found at http://tgs.gov.mb.ca/climate/Default.aspx

Submitted by: Pam de Rocquigny, Provincial Cereal Crops Specialist & Mike Wroblewski, Ag Meteorologist, MAFRD

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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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The Dreaded “F” Word – FROST

Given its sporadic nature, long-range forecasting of frost is nearly impossible. Rather, the climate record of an area is used to determine probable dates of frost based on long-term temperature records. While this will not provide an actual frost date in a particular year, it will present the likelihood that frost may occur on a certain date.

The “Date of First Fall Frost” maps at 50%, 25%, and 10% risk show the likelihood that frost will occur on or before the dates shown within the maps. A frost would be expected to occur 1 in 2 years at the 50% risk date, 1 in 4 years at the 25% risk date, and 1 in 10 years at the 10% risk date.

The extent of frost damage to a crop will depend on several factors. The crop type, stage, and hardening of the crop, the soil type and soil moisture, the actual air temperature, the duration of freezing, and the rapidity with which freezing takes place are all important. A drop in air temperature of short duration will cause less damage than a prolonged period at the same low temperature. When the air temperature drops to 0°C, cereal and other crops may not sustain damage. Rather, damage or total loss is more common when minimum temperatures drop below -2°C, often referred to as a killing frost.

For more information on Manitoba’s Agricultural Climate, please visit our website at  http://www.gov.mb.ca/agriculture/weather/agricultural-climate-of-mb.html

Submitted by: Pam de Rocquigny, Provincial Cereal Crops Specialist, Manitoba Agriculture

Information from the article “Risk of Fall Frost” by Andy Nadler, 2010

 

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