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A hard freeze in May isn’t ideal when 38 percent of soybeans (seven percent emerged) and 67 percent of corn (24 percent emerged) are in the ground, but that’s what a number of growers experienced earlier this week. From as far south as Missouri and Kentucky to the Midwest and Northeast, a late-season cold snap moved temperatures below freezing. We’ve had a number of questions this week regarding freeze damage on newly planted and newly emerged corn and soybeans. Here’s what we’re telling growers to look for and how to tell if there’s cause for concern.

Corn
In most cases, corn may only have cosmetic damage. Although it may look bad, it should still fare the cold temps just fine. Because the growing point in corn remains below ground, it is still protected by soil temps that are likely still above 28 degrees Fahrenheit. However, if the temperatures reach this point and remain that way for several hours, the growing point can be injured or even killed.

The same timeframe applies with a caveat for corn (five to seven days) with warmer temperatures. Corn requires growing degree units or heat units to grow. Colder than normal temperatures that result in negative or a loss of heat units will delay the normal growth and development process.

A quick reference on growing degree days is to take the daily high temperature, add it to the daily low temperature and then divide the sum by two. Then, subtract 50. For example, if today’s forecasted high is 53 degrees Fahrenheit and the forecasted low is 50 degrees F, this will result in 1.5 growing degree days (53 + 50 = 103 / 2 = 51.5 - 50 = 1.5). A corn plant’s normal processes won’t function until you reach 10 growing degree units. Therefore, it may take longer than five to seven days to see new growth if this trend were to continue.

Soybeans
Deciding how to proceed following a long duration cold snap on soybeans can be tricky. Not all cold temperatures are created equally. For instance, a spell of lethal cold temperatures will be more damaging than a brief frost of a few hours. Making informed decisions will have the greatest impact on yield and profitability.

Lethal cold temperatures for soybeans are defined as 28 degrees F, but merely reaching that temperature does not guarantee death of tissue. The ground can act as a heating barrier if days prior to the freeze were warm. Residue such as cover crops and ice can also act as insulators to protect the seed.

It’s important to remember that visible leaf tissue damage on soybeans does not guarantee plant death. Tissue will often turn a dark greenish black after exposure to lethal cold temperatures. However, if the axillary buds are unaffected, the plant may continue to grow without suffering permanent damage or yield loss.

Newly emerged soybeans are most susceptible because the exposed tissue from ground level to cotyledons represents the only live-growing tissue and growing points of the young plant. Damage from the soil surface to the cotyledons will likely permanently damage the young soybean plant.

Time is your friend in making these decisions. If the weather remains cool, plant growth and development will be slow, and it may take five to seven days to assess the true nature of the damage, if any. If after five to seven days there is no new emerging tissue, intervention and replant will be necessary to maintain productivity. If there is new tissue growth in five to seven days following a freeze with remaining cool temperatures, the soybean plant has survived and no intervention will be necessary. However, caution should be exercised. A freeze is a traumatic event for plant tissue and allowing adequate time for recovery is warranted. Allow the growth of two to three true leaflets prior to applying herbicides.

Regardless of what some people say, applying a fungicide, insecticide or any growth-promoting products is not helpful to frost damaged corn or soybeans. If you have questions related to your crops and the recent freeze, contact your local Stine sales agronomist. 

Growers know that planting season comes with many variables: timing, changing weather patterns, varying soil conditions, equipment failures, insects and more. In uncertain environments, seed treatments give control back to the growers so they can better protect their seed during its most vulnerable time — from germination to emergence.

More and more farmers are planting earlier in the season since soybeans respond well to early planting — if soil conditions and weather  patterns are optimal — and because they want to achieve maximum yield. Researchers from Nebraska determined that soybean yield declines about 1/4 to 5/8 bushel per acre for each day planting is delayed after May 1. While recommended planting dates for soybeans may vary from region to region, one thing is certain — growers are and will continue to plant early.

Growers who are planting soybeans early need to proceed with caution. Late spring temperature swings can leave soil cold and wet. As growers know, wet or water-logged fields leave seed and seedlings vulnerable to molds and infection from Phytophthora, Pythium, Rhizoctonia or Fusarium. Cool soil also delays germination, providing insects with more time to wreak havoc on seed and seedlings.

One way growers can ensure they’re maximizing the performance of their seed is by using fungicide and insecticide seed treatments. Researchers in Wisconsin found that seed treatments containing combinations of fungicide, insecticide and nematicide increased plant stands up to 10 percent. Over an eight-year period, fungicide seed treatments showed an average yield increase of 2.5 bushels per acre, according to Kansas State University Research and Extension.

Soybean growers have taken notice. In fact, the soybean industry estimates that up to 70 percent of seed planted in 2014 was treated. In 2008, only about 30 percent of seed was treated and even less — 8 percent of seed — was treated in 1996.

If you haven’t planted soybeans yet, there’s still time for seed treatments. Consider these scenarios to determine if seed treatments are right for your field. 

• Planting early. When spring weather conditions are cool and wet, fungicide seed treatments are an effective tool to stave off fungus and other infections. Insecticide treatments also help protect seeds and seedlings that are slow to grow in cool temperatures.
• Poorly drained or no-tilled fields. If your fields have a pattern of damping off and are more susceptible to root rot, seed treatments are a must. According to The Ohio State University Extension, farmers with poorly drained or no-till fields are most likely to see added benefits from using fungicide seed treatments.
• Replanting. Lack of stand establishment during germination is a sign of seedling disease. If you need to replant your fields, seed treatment is insurance for a good stand. Some farmers are valuing seed treatments as just as important as seeding rate, according to the University of Wisconsin-Madison Extension.

Stine has seed treatments that combine fungicides, insecticides and nematicides. Our selection of treatments will protect your seeds, seedlings and — ultimately — your bottom line. Learn more about Stine seed treatments at StineSeed.com.

Weather is an obvious factor when determining the right time to start planting. Even after you get seed in the ground, growers have to be cautious of the potential effects cold temperatures have on their crop, especially its viability after a certain growing point. Here are a few things to consider before planting early.

Newly Planted corn
Corn imbibes 50 percent of the water necessary for germination within three hours of planting, assuming there is adequate soil moisture for this to happen. This is the most susceptible time for newly planted corn because imbibing cold moisture can severely disrupt the germination process and cause serious issues in the developing embryo.

Typically, within three days after planting, no more moisture is being taken up by the seed and the germination process is well underway. At this point, injury can occur but is rarely fatal and rarely causes effects on yield. The exception would be if temperatures drop below 28 degrees Fahrenheit at the growing point. I recommend checking this temperature in the morning, prior to the sun hitting the soil. Remember, at the VE–V5 stages, the growing point will be three-fourths to one inch below the soil surface.

Emerged Corn
Corn that is emerged and at the VE–V5 growing point remains protected below the soil surface where there is an insulating factor against cold temps. The liquids within the corn plant act as an antifreeze and keep the tissue from freezing at the 28 degrees Fahrenheit mark. For temps below this, it is possible to see some frost damage on the leaf margins and tissue. However, this is rarely fatal or affects yield. The exception again would be the growing point and the temperature at the growing point.

Newly Planted Soybeans
Unlike corn, soybeans are not subject to imbibitional chilling. This does not mean that soybeans are immune to cold weather and rain; it simply means that they will not suffer germination and growth and development issues if they are subjected to cold temperatures and moisture. Soybeans are the ideal candidate for planting in questionable weather patterns.

Emerged Soybeans
Emerged soybeans can be injured by temperatures below 32 degrees Fahrenheit. However, the factors involved in determining the extent of the damage are row width, duration of cold temperatures and growth stage of emerged soybeans.

Narrow-row, drilled soybeans tend to hold in more ground warmth if soil temperatures have risen above 40 degrees Fahrenheit. This thicker canopy has the ability to hold in the radiant heat of the sun. However, as most soybeans either lie dormant waiting for moisture and temperature to germinate or will just have emerged, this benefit is not likely. Temperatures between 28–32 degrees Fahrenheit for short periods of time will not have a deleterious effect on young soybean plants; however, long periods in this temp range will have killing effects on emerged plants.

A little rain (or snow) that coats the plant or ground will also act as an insulator. Much like citrus growers who water lightly before a freeze and let the ice “insulate” the fruits or blossoms, the moisture can act in the same way.

Where do growers go from here? Patience is key! While soil conditions are better than we have seen in some areas in more than a year, an early rush to plant is not always warranted. Careful consideration should be given to the risk as well as the reward of early planting. For more information, contact your local Stine representative or your Stine regional agronomist for help.