Submitted by Anastasia Kubinec, Manitoba Agriculture
Originally posted May 8th and 30th, 2015…..re-post May 13, 2016 and now May 27, 2019.
Don’t assume because there is frost (or snow) on the ground, that your emerging crop in dead!
With the drop in temperatures in the past couple of days, there are a few things to keep in mind if the mercury dips below 0°C. The temperature is the instigator for causing frost, but whether it is -0.1°C or -4°C the damage inflicted is highly influenced on these other factors:
Short frost = < 2 hours, may not cause much damage if frost is light (above -1 to -2°C), crop type and staging is tolerant, conditions wet and crop has become acclimatized.
Short frost = < 2 hours, but hard frost (lower than -2°C), crops like canola are more sensitive to longer frost vs. cereals, damage can be variable in field and across area.
Long frost = > 2 hours, whether frost is light or hard the longer the negative temperatures the more time for damage to happen. Tolerance by crop type varies.
Other Environmental Conditions
Cloudy and wet – prior to a frost, cool temperatures slow plant growth and ‘hardens’ plants off, which will help them tolerate a frost. Also wet soil helps buffer the cold air effects on the plants, as wet soils change temperature slower than dry soils.
Sunny and dry – The combination of a dramatic drop in air temperatures when plants are actively growing then a brilliant sunny day after the frost event is where we have seen the most damage. Scouting after the frost (24 and 48 hours) is very important though to assess extent and percentage of field injury.
Field trash cover – increased trash in fields was seen to increase frost damage on very susceptible crops in the 2009 June frost
Spring Cereals – more tolerant than other crops types, can tolerant to temperatures as low as -6°C as growing point below ground until the 5 leaf stage.
Winter Wheat – can withstand very low temperatures for a short period of time (-11°C for less than 2 hours) up until the tillering stage.
Corn – smaller then V5, will recover from light frost as growing point below ground. Leaves probably will be killed, but plants will recover if the growing point ok.
Oilseeds – environmental conditions impact frost severity on susceptible canola and flax cotyledons. Resiliency increases at the 3-4 leaf stage (canola) or 2nd whorl (flax). Sunflowers are fairly tolerant up to the V4 stage.
Pulses – peas are most tolerant, then soybean, edibles bean are very susceptible even before emergence. Field pea crops are rarely lost to frost. Soybean are more sensitive, but the smaller the soybean plant the more tolerant they are – from emergence to cotyledon can withstand short light frosts.
Scouting After a Frost
Scouting should start 24 – 48 hours after the frost and continue for the 5 days following the frost event. Look for leaves wilting, looking “water-soaked” or see “frost banding”. Watch for new growth in the plant. You do not want to see plants wilted and not perking back up or pinching off on the stem near the growing point (canola, flax, soybeans). Also assess the area affected by frost, small areas or a few plants damaged are ok, as other plants emerged (or just emerging) will fill in those spaces. Large dead areas may need to be re-seeded.
If in doubt of what look for, call your local agronomists, local FPE Specialist with Manitoba Agriculture or the Crop Industry Branch.
For more specific details on what actually occurs to plants with a frost and crop specific details and symptoms to look for (and how long after a frost to do assessment) see Manitoba Agriculture’s Spring Frost Damage Bulletin.
Excellent question that we usually do not have to think about in early May!
As most grain is still cold in the bin and with the rapid increase in outside temperature, the potential for spoilage could still occur in stored canola and flax still in the bin from 2015 harvest.
If you think this might be an issues, check what is the seed moisture and the temperature is again. The 5C, 8.5% moisture canola in March had no risk of spoilage, but a 35C, 8.5% moisture canola does. Flax is susceptible to spoilage as well, if the grain gets very warm in the bin and the moisture is over 8%. If things are all good today, check in a couple of days again if the May heat wave continues and consider turning on the aeration fan and open up the bin hatch at the top of the bin to let humidity escape.
This question came in as a concern over the potential of condensation to form on the bin walls from the hot outside air hitting the cold grain in the bin. Aeration could be used as a tool with the hot, but very dry air to warm the grain slowly and move some of the potential humidity out through the top vent or hatch. Monitoring though is key and should continue until the grain is delivered to catch spoilage issues. A great resource on more about aeration and grain in storage can be found on the PAMI (Prairie Agricultural Machinery Institute) website www.pami.ca/crops/storage and at the Canadian Grains Commission https://www.grainscanada.gc.ca/storage-entrepose/ssg-de-eng.htm
Manitoba Agricultural Services Corporation (MASC) has released an early version of the 2014 yield report with 99.8% of the Harvest Production Reports (HPRs) keyed in. The table below summarizes the 2014 average yield by crop type based on the harvested acres, as well as comparisons to 2013 and a 5-year average (2009 to 2013).
In February 2015, MASC will release their annual Yield Manitoba publication and update their Manitoba Management Plus Program (MMPP) website (http://www.mmpp.com/mmpp.nsf/mmpp_index.html) where further information on yields and acres by variety will be released. Additionally, the data will be more complete in February as all HPR’s will be keyed in.
Submitted by: Pam de Rocquigny, Anastasia Kubinec & Dennis Lange, Crop Specialist with MAFRD
Special Thanks to Doug Wilcox, MASC, for providing the 2014 data!
One of our most used extension messages is seed early!
In a year that is later, this may cause some concern that seeding into the second half of May is not going to have good crop yields. Typically seeding earlier does normally translate into higher yields, but good yield potential remains when seeding throughout the month of May, provided you don’t compromise the seeding operation.
Things Other than Seeding Date That Influence Yield:
Using clean seed with high %germination
Applying the appropriate fertilizer nutrients and rates to support yield goals
Seeding for a good plant stand – taking in account TKW, %germination and seed mortality!
Seeding into a firm seedbed
Seeding into soil warm enough to result in quick germination and emergence
Timely weed control
Timely fungicide application if needed
Appropriate harvest operation timing
Table 1: Crop Yield Response to Seeding Date (2005-2013)
Soil temperature is a useful gauge for timing when crops are seeded. Table 1 shows the minimum germination temperatures for various crops. These values should be regarded as approximate since germination depends on several factors. If the soil is too cool, germination can be delayed which can result in uneven or inadequate seedling emergence.
How do I measure soil temperature?
Determine how deep you will be seeding. Then place your soil thermometer at that targetted depth. Take two measurements throughout the day: one in the morning (8am) and one in the early evening (8pm) . Average the two readings to determine the average soil temperature.
MAFRD recommends that you take readings for two to three days to establish a multiple day average, and reminds you to measure temperature in a number of locations in the field, to account for field variability. Still not sure, see soil temperature data for various locations across Manitoba is available from MAFRI’s Ag-Weather Program: http://tgs.gov.mb.ca/climate/SoilTemp.aspx. This can be used as a guideline for an area, but in-field measurements are going to tell you what is actually going on in your field!
Table 1: Minimum Germination Temperatures for Various Crops
Sources: North Dakota StateUniversity Extension Service, Alberta Agriculture & Rural Development and Canola Council of Canada
Flax can be a frustrating crop to straight-cut combine with the bolls dry and ripe and the stalks still grass green and potentially wrapping around the reel.
The use of a chemical harvest aid or dessicant will not help to ripen flax faster, but is can greatly increase ease of harvest by killing and drying out green stalk material, weeds and can be effective for use in perenial weed control. If bolls and seed are getting close to maturity, but the stalks green and maybe you have weed issues, dessication may be a very good option. If you are planning on dessicating, 75-80% of the bolls should be brown. For product choices and rates refer to the “Guide to Field Crop Protection”. Harvest of flax after application should occur when sample tests dry, typically 7 or more days after application.
If your bolls are mostly still green, please wait a little longer. As mentioned above, using a chemical harvest aid/dessicant does not speed up seed maturity. If applying too soon, it can actually reduce yields due to smaller seeds or shriveled seeds that don’t make it into the tank.
It very well could be herbicide injury or potentially environmental stress damage. Applying herbicides especially those with a broadleaf control component under very hot and humid conditions can damage flax. The growing point may be damaged even more if spraying occurred after flax is 6 inches or taller. Spraying flax when the temperature has not exceeded or is not going to exceed 28C within a 48 hour timeline around the herbicide application will help reduce the injury to flax. Also, only spraying products that are registered on flax will help reduce injury as they have been tested and approved to provide acceptable weed control without causing unacceptable crop injury.
If you are already seeing symptoms of aster yellows in flax, it is too late for any control. The infection would have occurred from aster leaf hoppers that blew in from the south and were feeding 3 or more weeks ago. There are no fungicides available to control aster yellows. In field crops, insecticides are generally considered of little value in management of this disease, as research shows a single insecticide application would have a low probability of being of much value, and multiple applications (as done in horticultural crops) would not be practical in field crops. Because damage is so visible, it is very easy to overestimate the amount of damage across a field, so assess the crop carefully before making conclusions.