Effect of Greensnap Injury on Corn Yield Potential

• Greensnap occurs mainly in the western to central corn growing area where thunderstorms with high winds are more prevalent.
• Rapidly growing corn in late vegetative stages to tasseling is most vulnerable to greensnap.
• The effect of greensnap on yield potential depends on how many stalks were snapped and where on the stalk the breakage occurred.

Greensnap Injury and Corn Growth

Greensnap, also known as brittle stalk or brittlesnap injury, occurs when strong winds cause corn stalks to snap at a node. This weather-related occurrence typically happens when internodes are rapidly elongating, making corn plants particularly vulnerable to damage.

There are usually two windows of potential greensnap injury, growth stages V5 to V8 and V10 to R2 (Figure 1). Growth regulator herbicides can increase the potential risk of greensnap during the V5 to V8 window when the growing point is just emerging from the soil line. The corn plant is going through the most rapid rate of growth from growth stages V10 to R2. In a period of 17 to 21 days corn grows from around 4 feet to its mature height of 7 to 10 feet. During this rapid stage of growth, leaf surface area increases logarithmically. This rapid growth and increase in surface area coincides with the period of greatest potential risk of severe thunderstorms in July and early August. Typically, greensnap injury is observed at the primary ear node or the node above or below the primary ear node. Wind speeds above 80 miles per hour can result in breakage at nodes above or below these typical sites. Once a node has stopped expanding, cell walls are strengthened by the deposition of lignin that prevents breakage at that node. Straight line wind events after R1 or R2 may result in stalks kinking over or even breaking between nodes, but not actual greensnap stalk breakage, which occurs at a node.

Assessing Injury

The factors with the largest impact on greensnap damage in a particular field are the timing and severity of the wind relative to corn growth stage. Damaging thunderstorms that occur in early morning hours typically cause the most damage during the V10 to R2 growth stage. At the base of every node is a region called a meristem, which is an area of rapidly dividing cells. Stalk growth occurs as turgor pressure from water in the stalk expands the size of these newly divided cells. Corn plants are most brittle when turgor pressure is the greatest in early morning hours, when plants have taken up water overnight and are not under the heat stress of higher daytime temperatures.

Damaging winds often occur in the first minutes of a severe thunderstorm before soils are softened by rain. Fields with strong, deep root systems in dry, firm soil may have more greensnap injury than fields with shallow root systems. Weaker root systems tend to lodge under similar wind conditions. Greensnap injury typically occurs at the node still undergoing rapid expansion but is not yet strengthened by lignin and other structural materials in the cell walls. Neighboring fields may break at different levels or different nodes because product maturity, planting date, and other management factors can result in different nodes being vulnerable for a specific field when a wind event occurs.

The effect of greensnap on yield depends on the number of plants snapped in a field and where the breakage occurs on the stalk.² In many cases, yield loss for a greensnap event is directly related to the number of plants snapped. For example, if 10% of the plants are broken at a lower node or near the base of the plant, a grower can expect a 10% yield reduction.³ Depending on the timing of the greensnap event, any adjacent, uninjured corn plants may have already determined maximum production of the ear and may not have the ability to compensate for reduced plant competition. Stalks that break above the ear will usually continue to grow and produce an ear; however, yield reductions may occur if nearby plants shade the broken plant.² When the stalk breaks at a node below the primary ear, an ear may form at a lower node, but this ear may not receive enough pollen to produce many kernels.² A study conducted at North Dakota State University from 2015 through 2017 assessed the effects of greensnap injury to corn (Table 1). The study evaluated corn yield loss resulting from three levels of simulated injury (25, 50, and 75%) during different stages of corn growth (V12, V15, V18). Overall, results showed that yield losses increased with a higher percentage of plants damaged and when injury occurred at a later growth stage.

Additional Considerations

Straight line winds during a severe thunderstorm are highly variable and unpredictable. This variability is easier to see when assessing damage to trees, grain bins, buildings, or telephone poles. Variability can also occur in corn fields where straight-line winds result in narrow zones of destruction with highly variable patterns in fields. A frustrating aspect of assessing wind damage is that it is often the highest yield potential fields that have the highest level of crop injury. A University of Nebraska study found that there was a direct correlation to higher rates of nitrogen and increased severity of greensnap damage.¹ Crop management necessary for high yield potential contributes to rapid growth, which in turn can influence the level of wind injury. Yield loss for pinched stalks or root-lodged plants can be more difficult to estimate, as the plant may be able to reorient to a vertical position and produce an ear.

Managing the Risk

Planting corn products with different maturities and spreading out planting dates can help widen the window of corn growth and development for a specific storm event. When considering the risk of greensnap injury, keep these additional points in mind:

• Factors that favor early-season corn growth such as high nitrogen, phosphorus, and potassium fertilizer rates, tillage, and high organic matter can increase greensnap susceptibility.
• Follow the pesticide labels for timing, tank-mix partners and additives for all post-emergence applications.
• Crop insurance can help protect financial risk from weather-related crop injury. Notify your crop insurance provider of any damage following a storm event to determine if compensation is available.

Sources

¹ Elmore, R.W., Hoffmeister Jr., G., Klein, R., and Marx, D.B. 2003. Corn greensnap from extreme wind is influenced by several factors. Crop Management. Vol. 2, Issue 1. https://acsess.onlinelibrary.wiley.com/doi/abs/10.1094/CM-2003-1212-01-RS.

² Thomison, P. 2017. Wind damage in corn - “green snap” and root lodging. Ohio State University Extension. https://agcrops.osu.edu/newsletter/corn-newsletter/2017-21/wind-damage-corn-%E2%80%9Cgreen-snap%E2%80%9D-and-root-lodging.

³ Licht, M. 2020. Greensnap. Iowa State University. https://crops.extension.iastate.edu/encyclopedia/greensnap.

⁴ Ransom, J. 2018. Green snap in corn. North Dakota State University. https://www.ag.ndsu.edu/cpr/plant-science/green-snap-in-corn-07-05-18.

Web sources verified 6/2/25. 1214_244102