Southwest Michigan field crop update – May 14, 2020

Eric Anderson<eander32@msu.edu> and Lyndon Kelley<kelleyl@msu.edu>, Michigan State University Extension - May 14, 2020

Cold weather appears to be behind us with warmer temperatures predicted for the rest of May. Now is the time to scout and determine the extent of injury that may have occurred during the recent freeze event.

Figure 1. Overnight low temperatures at select MSU Enviroweather stations in south central and southwest Michigan. Aside from a few “cold domes” around Kalamazoo County, most areas saw lows from 24-30 F, but most locations were below the critical 28 F for several hours.

Weather update

We have some good news and some bad news. Most people opt for the bad news first, so here we go. Temperatures during the deep freeze that lasted a full four days set us back at least 5 degrees Fahrenheit in soil temperatures, several more days in accumulated heat units, and brought overnight temperatures last Saturday, May 9, that were low enough for several hours to cause concerns about crop injury. In Figure 1, we can see that air temperatures in several areas in and near Kalamazoo County reached all the way down to 20 F on Saturday morning. Since 28 F is generally considered the temperature where injury can occur in many crops, this was not good news. See the “Crop update” section below for pictures of impacts to several crops.

Figure 2. Mean temperature departure from normal for May 6-12 (left) and minimum temperature on Saturday, May 9. This cold event was definitely one to remember. Graphics courtesy of Jeff Andresen.

Figure 3. Growing degree days compared with normal from March 1 through May 13. As predicted, we have been dropping further and further behind and are now a solid two-plus weeks behind in heat units.

Figure 4. High and low soil temperatures (2-inch depth) and average air temperature (yellow is projected) according to the MSU Enviroweather station at Mendon. We only lost about 5 F in soil temperatures during the deep freeze, but we should see minimum soil temperatures well over 50 F by next week.

Now for the good news. Looking back over the past couple of weeks, precipitation was roughly 50% of normal, which freed many up to get a considerable amount of field prep and planting done. We now have a “week off” with rainfall predictions as high as 3 inches from now through Monday, May 18. Spring temperatures are also approaching with daily highs in the 70s next week and—wait for it—even approaching 80 F by late next week. These conditions will be prime for getting the crops that were planted out of the ground quickly.

Predictions for the end of May are also calling for warmer than normal conditions, and although the June outlook won’t come out until the end of next week, MSU Extension’s agricultural meteorologist Jeff Andresen says they should be pointing toward warmer and wetter than normal weather.

Figure 5. Precipitation over the past 14 days, reported on May 14 in inches (left) and as a percentage of normal (right). Dry conditions resulted in a lot of field preparation and planting being done in the southwest.

Figure 6. The 10-day forecast for Centreville, Michigan, as of May 14. Do I see an 80-degree prediction here?

Figure 7. Precipitation forecast for May 14-21. All of this is predicted to fall by Monday morning, May 18.

Figure 8. The 8-14 day outlook from May 21-27 for temperature (left) and precipitation (right). The 6-10 day outlook predicts even higher chances for warmer-than-normal temperatures and leaning toward wetter than normal.

Crop update

Corn and soybean

As noted above, the two newsworthy topics are the planting progress achieved during the drier weather these past two weeks and the potential crop injury associated with the freezing temperatures of this past week. As of May 10, 37% of the corn crop in Michigan was planted, a full 25% more than the previous week and 11% more than the five-year average. Only 3% of that had emerged, which is a good thing with regards to avoiding freezing air temperatures.

Similar progress was made in soybean with 35% planted (23% ahead of average) and 2% emerged. What did emerge ahead of the freeze last Saturday looks like it sustained significant injury. Fortunately, most of what has emerged this week looks like it has sustained less severe injury, if any. MSU Extension soybean educator Mike Staton says we’ll need to scout after beans emerge to look for signs of imbibitional chilling that may have occurred for those crops that were planted right before (or during) the deep freeze.

Figure 9. Planting progress in Michigan as of May 10 according to the USDA Crop Progress report. Thanks to the dry weather last week, we are ahead of the five-year average with both crops.

Figure 10. Corn that emerged prior to last Saturday. Scouting this field over the coming week will show to what extent any freeze injury occurred. Photos by Lyndon Kelley, MSU Extension.

Figure 11. Soybean in early April that had emerged prior to the freezing temperatures last Saturday. Photos by Lyndon Kelley, MSU Extension.

Figure 12. Soybeans that had just emerged prior to the freeze event on May 9. The unifoliate leaves were scorched on some plants (left) but remained healthy on others (right). Although certain varieties normally have a purple hypocotyl (middle), it appears beans in this field may have suffered freezing injury. Scouting in the coming week will determine the extent of any injury. Photos by Eric Anderson, MSU Extension.

Wheat/small grains

Most wheat in the region is at jointing in Feeke’s 6 (first node visible), 7 (second node visible) or 8 (flag leaf emerged). According to the most recent USDA Crop Progress report, 59% of Michigan wheat was rated excellent or good and another 32% as fair. Figure 13, taken from the bulletin “Spring Freeze Injury to Kansas Wheat” by Kansas State Extension, shows that the more advanced the wheat, the more susceptible it is to freeze injury. According to Table 1 from the same source, wheat at jointing is susceptible to injury at 24 F, which was measured at many locations in the region last weekend.

On the MSU Extension Field Crops Team’s Virtual Breakfast this week, wheat specialist Dennis Pennington talked about how to scout and assess freeze injury. Dennis also wrote an article and produced a YouTube video describing further how to scout and identify freeze injury in wheat.

Figure 13. Temperatures that cause freeze injury to winter wheat at different growth stages. This graph is taken from “Spring Freeze Injury to Kansas Wheat” by Kansas State Extension, so the timeline on the x-axis does not exactly align with ours.

Table 1. Symptoms and yield effect from freeze injury to winter wheat at different growth stages. This table is taken from Spring Freeze Injury to Kansas Wheat by Kansas State Extension.
Growth stage	Approximate injurious temperature (2 hours)	Primary symptoms	Yield effect
Tillering	12 F (-11 C)	Leaf chlorosis; burning of leaf tips; silage order; blue cast to fields.	Slight to moderate
Jointing	24 F (-4 C)	Death of growing point; leaf yellowing or burning; lesions, splitting or bending of lower stem; odor.	Moderate to severe
Boot	28 F (-2 C)	Floret sterility; spike trapped in boot; damage to lower stem; leaf discoloration; odor.	Moderate to severe

Figure 14. Wheat stem at Feeke’s 7 showing two nodes (circles). Slice the stem just above the uppermost node (arrow) to expose the growing point.

Figure 15. A healthy (left) and injured (right) wheat growing point. To find the growing point, slice the stem lengthwise just above the uppermost node. If it is yellow/green and turgid (firm), it is healthy, but if it has turned white or brownish, is flaccid (limp) and possibly has a foul “silage” smell, it has been injured. Photos from “Spring Freeze Injury to Kansas Wheat” by Kansas State Extension.

Figure 16. Growing point of wheat (left and center) and the head of barley in the boot (right) taken from fields in St. Joseph County. Photos by Eric Anderson, MSU Extension.

Figure 17. Wheat field in St. Joseph County. Some leaf scorching was observed although the overall health of the crop looked good. Scouting in the coming week will help determine the extent of injury to the growing point. Photos by Eric Anderson, MSU Extension.

Figure 18. Barley at Feeke’s 9-10 with the head in or nearly in the boot. Purpling of the stem and leaves could be due to nutrient deficiencies (e.g., phosphorus) or a buildup of anthocyanin pigment due to plant stress, but it is not itself a good indicator of injury. Split open the stem or flag leaf sheath to reveal the head and note color, firmness, odor, etc. Photos by Eric Anderson, MSU Extension.

Potato

Cold soil temperatures have affected potato development and emergence this spring. The following observations are provided thanks to Karl Ritchie, lead agronomist with Walther Farms. “A handful of potatoes had emerged last Friday before the frost burnt them back. We expect emergence by the end of this week. It has been a cold slow spring for potato emergence. The crop is taking an extra two weeks to emerge compared to normal, but we had good planting weather and got the crop planted about one week ahead of schedule. Bottom line, about one week behind.”

Alfalfa

Established stands are 6-12 inches tall with slower growth this season due to cold temperatures. Established alfalfa stands can be damaged at temperatures of 25-27 F or lower with injury affecting leaves, buds and growing points according to Steve Barnhart at Iowa State University. As can be seen in Figure 19, it is possible for only parts of plants to be injured while adjacent plants appear unaffected. For alfalfa seedlings at the second trifoliate leaf stage (and older), “seedlings become more susceptible to cold injury and may be killed by four or more hours at 26 F or lower temperatures,” according to Barnhart.

Figure 20. Alfalfa seeding that had emerged prior to Saturday, May 9. Photos by Lyndon Kelley, MSU Extension.

This article was published by Michigan State University Extension. For more information, visit https://extension.msu.edu. To have a digest of information delivered straight to your email inbox, visit https://extension.msu.edu/newsletters. To contact an expert in your area, visit https://extension.msu.edu/experts, or call 888-MSUE4MI (888-678-3464).