Connect with Local Experts
If you feel like the only thing predictable about the weather is its unpredictability, you’re not alone. From time immemorial, growers have had to navigate uncertain weather conditions in crop production to protect and optimize their yield. So, what happens when the unexpected occurs and your corn crop gets bitten by a killing frost, pummeled by hail, flooded by excessive rainfall, or baked in a summer drought? Learn when your crop is most at risk for weather damage and discover what to expect if your crop encounters frost, flood, hail, wind, or drought damage.
📸: BASF employee/Featuring frost on corn leaf.
The highest risk of frost damage in corn typically occurs in April and October. While spring frost can impact seedlings' health, fall frost damage can result in yield reduction.
Spring freezes can damage early-emerging corn seedlings when air temperatures drop near the mid-30s F or below. Damage is more likely in low areas of the field due to cold, dense air. Soil types can vary in how they respond to frost damage, with peat or sandy soils posing the highest risk.
Additionally, fields with significant surface residue cover or row-cultivated fields that have undergone recent cultivation are at greater risk for more severe frost damage. If the coleoptile and the top of the shoot freezes, emergence may be halted and seedlings may leaf out underground.
Thankfully, frost damage that occurs prior to V5 typically has limited long-term impact on yield because the growing point is still sheltered below the surface of the soil. However, even prior to V5, temperatures that drop near or below 28 F may penetrate the soil, potentially causing long-term damage to the growing point. Seedlings take longer to recover from frost damage if temperatures remain low following the initial frost. Recovery time may be slowed if daytime high temperatures linger around 40 F to 50 F.
📸: @Ratikova via Canva/Featuring an image of fall frost on corn.
Corn-killing freezes occur when temperatures drop to 32 F for at least four hours, or to 28 F for a mere few minutes. Lethal cold temperatures halt photosynthesis, subsequently stopping the metabolic processes that allow for any dry matter accumulation beyond the killing frost.
Fall frost damage causes a delay in the grain reaching desirable harvest moisture content due to kernels reaching black layer or physiological maturity, but yield losses are generally insignificant if frost occurs when grain moisture is below 35%.¹
Frost that hits corn prior to maturity may result in smaller, misshapen kernels that are more susceptible to breakage, impacting critical post-harvest grain drying, handling and storage. Fall frost damage can lead to chaffy, poorly filled ears with subsequent lower test weight. When uninterrupted by a killing frost, the natural maturation process creates a hard, protective coat over each kernel. Early death due to frost makes this coat weaker and prone to breakage, resulting in potential dockage for broken kernels during harvest.²
Symptoms are typically apparent one to two days after the frost event. However, premature assessments of frost damage can easily misconstrue the amount of damage and loss, so patience is a virtue here: Wait three to five days after a frost to get the most accurate assessment of the damage to your crop.
Symptoms of spring frost damage to corn seedlings include:
To diagnose the severity of spring frost damage to corn seedlings, dig up plants, splitting the stems to look at the growing point and plant tissue right above it.
If you find tell-tale signs of frost damage in the growing point of the tissue within 0.5" above the growing point, recovery is unlikely.
Symptoms of fall frost damage to corn include:
📸: @Ihor Martsenyuk via Canva/Featuring snow covered corn crop in unharvested corn field.
The likelihood of frost-damaged corn recovering depends on when the freeze occurred. At early growth stages, energy reserves in the seed and leaf give young corn plants the greatest chance of recovering from a freeze. Frost damage that occurs before V5 is generally unlikely to have significant yield impact. If frost hits after V5, the chances of recovery are dependent on the amount of leaf area that is damaged. It isn’t necessarily a matter of whether corn will recover from late-season frost damage, it’s a question of how severely the frost damage will affect grain quality.
Typically, it’s best to let spring frost-damaged corn seedlings recover on their own, as any form of intervention could actually worsen the damage. If the weather cooperates, corn seedlings can bounce back, developing new leaves in as few as three or four days after the frost event. Depending on the severity of the damage, replanting may be a consideration. Iowa State University research indicated that at 55% to 70% defoliation due to frost, leaving the field to recover on its own was most economical. In cases where frost damage exceeded 70% defoliation, replanting was the best choice.³
Fall frosts can reduce storage life unless care is taken to gently dry, handle and aerate damaged corn that did not mature naturally. Frost-damaged corn will still dry down, but the process will take longer than usual. Since a killing frost prematurely terminates the normal growth and development process, frost-damaged corn typically has increased kernel moisture, which delays the drying period and harvest time. Keep in mind the apparent grain moisture level may be deceiving since the outer part of the kernel dries faster than the interior of the kernel.
Read more about frost damage on Grow Smart® Live:
📸:@Daren Mueller, Iowa State University, Bugwood.org/Featuring a photo of a flooded corn field.
The type and extent of damage caused by excessive rainfall and flooding largely depends on what growth stage the corn is in when the deluge hits.
The typical timeframe for excessive rainfall and flooding is May and June. Submerged or saturated field conditions have the greatest impact on corn from pretasseling (VT) to silking (R1), the most critical stages of corn development.⁴
Flooded corn may experience any or all of the following:
For example, surviving plants may show yellowing, indicating a lack of nitrogen (N) or sulfur (S).
📸:@BASF internal photo/Featuring a photo N loss in corn after high rainfall.
📸:@BASF internal photo/Featuring a photo N loss in corn after high rainfall.
Regardless of the growth stage of the crop, the level of nitrogen leaching and decreased nutrient availability due to flooding may create a critical nitrogen deficiency later in the growing season.
Root damage caused by submersion can also hinder nutrient uptake, potentially requiring sidedress of nutrient applications.
When assessing flood damage in corn, wait about five days after flood waters recede to get the most accurate assessment. Pull up a few plants and inspect the growing point.
If the growing point is soft and dark, this means the plant is dying. If it is still cream colored, the corn will likely recover with minimal yield reduction if optimal growing conditions are maintained for the rest of the season.
Corn survival rates after flooding increase dramatically if the growing point is not completely submerged (as with older corn) or if it is submerged for less than 48 hours.⁶
Additionally, temperature impacts survival rates. If temperatures are greater than 77 F, plants may not survive as long as 24 hours of flooding.
If flooding occurs prior to emergence and soil surface crusting is present, using a rotary hoe across the field to breakup the crust layer or cultivating between rows can help corn roots access necessary water and oxygen, prompting seedling emergence.
Additional nitrogen may be needed in corn fields that have survived flooding and the associated nutrient leaching and nitrogen losses that may have occurred.
You can use a pre-sidedress soil nitrate test (PSNT) to evaluate if supplemental nitrogen is needed.
Read more about the effects of flooding on Grow Smart® Live:
📸: @ProdavacSlika via iSstock/Featuring an image of hailstones in a corn field.
Hail can be a financially devastating adversary to corn growers, with hail storms between June and September resulting in yield losses of approximately $52 million annually.⁷
Corn yield can be impacted by hail damage in the following ways:
About half of all hail storms hit the Midwest between March and May. Thankfully, these early-season storms do not typically have a significant impact on yield since they occur either before planting or when corn seedlings are too small to be damaged. And if damage does occur, fields can often be replanted without incurring too much of a yield penalty. However, approximately one-third of all hailstorms happen between June and September, when the effects of defoliation can have a severe impact on yield. In the late vegetative stages and the all-important tasseling phase, hail can be severely damaging. If the tassel breaks off due to hail, no grain will be able to form on the ear.
The primary symptoms of hail damage in corn include:
Plant regrowth may take three to five days to begin, so it’s recommended to wait that long before scouting for and estimating hail damage and recovery potential. Keep in mind that at first, hail damage may look more severe than it is, so waiting is key to get the most accurate assessment.
When you scout, split stalks and assess the growing point, and look for discoloration or signs of soft rot. If your plants show superficial signs of stalk bruising, again split them open to determine the severity of the bruising.
The severity of whorl damage can be more difficult to determine right away. Sometimes new leaves can emerge through a damaged, tightly bound whorl after about a week of growth. Other times, leaves become so tightly bound in the whorl that they cannot emerge and the plant is lost. Assessing whorl damage is a waiting game — it is nearly impossible to gauge the final plant population in the first few days after hail.
Also examine corn ears and calculate the percent of damaged kernels. This is typically calculated by selecting ears from 10 consecutive corn plants and counting the number of damaged kernels on all the ears. Add up the total number of kernels on all 10 ears, and determine the percent of total kernels damaged to find the percent of loss due to direct ear damage.⁸
📸: @P.F. Byrne, Bugwood.org/Featuring a photo of wind-flattened corn.
Yield loss from corn wind damage is not typically caused by the damage itself, but by the inability to harvest the damaged corn. Corn plants are resilient and can often right themselves enough to continue through the maturation process. Understanding how wind damage affects corn and learning when and how to identify damage can provide you with the best plan to recover from corn wind damage.
A combination of saturated soils and strong winds can result in lodging, when corn plants lean and pull up their shallow roots. Typically, these root-lodged plants are able to stand back up, albeit with goose-necked stalks. Yield reductions are minimal when wind damage occurs at V10 to V12 stages, but yield impacts increase when corn is damaged at the V13 to V15 stages, and the highest risk of significant yield reduction is reached when wind damage occurs at the V17 stage or later.
Light lodging due to wind damage may result in 5% loss, while severe lodging could bring up to 30% loss (in severe lodging, plants can domino onto each other, blocking out access to sunlight). Lodged corn also is more susceptible to disease.
Stalk breakage, a condition known as greensnap, can also occur as a result of strong winds. Your corn is most likely to encounter greensnap during rapid vegetative growth between the V10 stage and tassel emergence, when stalks are brittle. This is the deadliest kind of wind damage. The percentage of stalks broken and the location of the breaks indicate the amount of yield loss. If plants are broken or snapped below the ear, they are total losses. Plants with stalks broken above the ear can produce grain.
Secondary concerns related to corn wind damage include:
📸: BASF employee/Featuring wind damaged young corn crops.
Scouting drones work well to get an initial assessment of wind damage across the field. It is recommended to wait 5 to 10 days to see how the crop can stand back up and start recovering. You can determine how to manage wind-damaged corn by analyzing the extent of the damage.
Flattened corn fields can survive with minimal yield reduction if wind damage occurs early enough for plants to right themselves and place silking ears in proper position prior to pollination. If stalks are just bent, but not broken, water and nutrient uptake can still occur (albeit at a slower rate). However, wind damage in later vegetative growth stages is more likely to cause unrecoverable lodging since stalks are more brittle and less likely to reorient themselves, negatively impacting pollination and yield.
If grain is mature, lodged corn that doesn't right itself should be harvested first with reduced combine speed and gathering snouts as close to the ground as practicality allows. Work against the grain of the leaning stalks, which is most effective to help lift the plants up instead of flattening them further.
Read more about how to handle wind-damaged corn on Grow Smart® Live:
Corn is most susceptible to severe yield reduction when drought conditions occur during V13 to silking, but overall yield potential can be reduced regardless of when heat and drought stress occurs. The level of yield loss varies based on the time and length of the drought stress.
📸: @marnag via Canva/Featuring drought stressed corn.
Yield reductions are dependent on the growth stage and severity of the drought conditions:
In the early vegetative growth stages, leaf rolling is one of the primary symptoms of drought stress in corn. If drought conditions persist for several days, you may notice reductions in leaf elongation and plant height.
In later growth stages, the following symptoms may occur:
Drought stress in corn directly affects the final number of kernels in a myriad of ways, including:
📸: BASF employee/Featuring 7 DAT Right Treated with Priaxor® fungicide before Heat index of 90-100 degrees during June 9-11 (Treated June 8).
Learn how to optimize your corn yield this year:
Experts are available to help you make your decisions. Reach out to your seed retailer, a nearby extension office agent, or a seed company professional like your regional BASF representative.
Always read and follow label directions. Priaxor and Grow Smart are registered trademarks of BASF. © 2024 BASF Corporation. All Rights Reserved.
Stay informed with the latest & Most Important News
Your email address
I consent to receive newsletter via email. For further information, please review our Privacy Policy
Corn
Last
454.5
Change
+0.5
Time
January 9, 2025
