Green Snap Injury

INSIGHTS

• Green snap is the breakage of corn stalk nodes.
• The growth stage when damaging wind events occur plays a significant role in potential green snap damage.
• Green snap injury in corn has the potential to significantly reduce yield potential.

Introduction

Green snap, otherwise known as brittle snap, is the breakage (snap) of corn stalk nodes resulting from excessive winds (Figure 1). Most susceptible during these weather fronts, are corn plants that are in rapid canopy growth stages prior to pollination.

Green snap occurs yearly, but only a few acres are affected in most years. It is predominantly seen in the Western and Northern Corn Belts when rapid corn growth is mixed with high wind speeds. Green snap can be seen at the lower nodes (close to the soil surface) and nodes at or above the ear. During accelerated growth, stalk internodes elongate rapidly, and the node and internode tissue are packed with water. Cell walls have not matured, and very little structural lignin has formed, resulting in water-packed cell walls that are quite fragile. It is at this stage that the corn plant is susceptible to high winds and breakage at the nodal “plates”. 

Timing and Growth Stages

The two most common times when green snap risk increases are when the growing point is at or just above the soil line (V5 to V8) and the two weeks period prior to pollination (V12 to R1). The two specific time periods are when plants are normally going through a rapid growth phase in which internode plant cells are rapidly elongating, making them extremely vulnerable to breaking when under pressure. Due to the sensitivity at these specific timings, damage is often associated with wind events from storms.

Green Snap at V5-V8

• More susceptible after a period of favorable precipitation and temperatures that encourage good growth followed by a wind event.
• Snapped plants will not recover as breakage occurs below the active growing point.
• Tillers may develop following green snap but will not yield a productive plant.
• Yield impact will vary depending on the number of plants that were not snapped.
• Unaffected plants will partially compensate for lost plants when snapping occurs early due to the reduced plant competition.

Green Snap at V12 Through Tasseling

• Plant undergoes most rapid growth at 2-4 inches per day with rapidly expanding leaves and height, making the plant more susceptible to wind events.
• Plants are prone to snapping at ear node and nodes just below or above it.
• Ear shoots may develop after snapping, although grain production is not likely or will be greatly reduced due to the lack of leaf surface area for photosynthesis.
• Snapping at this time can cause more severe yield loss due to being too late to compensate for reduced plant stand. Yield loss is dependent on the severity of plants broken.
• When maximum plant height is achieved upon tassel emergence, internode cell elongation stops, reducing susceptibility to future snapping.

Yield Loss Associated with Green Snap

• Yield loss associated with green snap is based on where the breakage took place on the plant along with the number of plants affected. The loss of harvestable ears per acre is the primary cause of yield loss associated with green snap. Research has differed in yield loss potential from green snap over time. The University of Nebraska-Lincoln concluded that yield loss decreases approximately 1% for every 1% in stalk breakage (1:1 ratio).¹ However, several subsequent research studies, by university and internal Golden Harvest agronomy research, have suggested that the yield loss from stalk breakage is generally much less severe with modern corn hybrids² (Table 1).

Golden Harvest Hybrid Research

Golden Harvest® corn hybrids are routinely screened for sensitivity to green snap. Trials are conducted every year using helicopters to apply high winds to hybrids at two specific growth stages (Figure 2). Snapped plants are counted to calculate percent green snap and aid in discarding susceptible genetics prior to commercialization. Using this type of measurable characteristic also helps to identify stronger genetics and predict how hybrids will perform in areas highly prone to green snap.

Even the most tolerant hybrids are still somewhat susceptible to green snap when well-timed wind events occur at the most susceptible growth stages.

Multiple Factors Influence Severity of Snapping

Multiple factors are involved in influencing the potential severity of green snap damage. It may be difficult to understand why some fields or hybrids were affected and others where not. Environmental or management conditions that optimize for high yield potential are also favorable for causing green snap. Subtle changes in management practices, such as a planting date that slightly delayed growth, can result in differences within the same hybrid that otherwise grew under the same conditions. The following list includes some of the most common factors that contribute to green snap severity differences:

• Time of day the wind event occurred – plants are most turgid in the morning hours from overnight moisture uptake
• Severity of wind speed, gusts and direction
• Stage and rate of growth – most susceptible during rapid internode elongation
• Hybrids can vary in length of time they are sensitive to green snap in a growing season
• Herbicide – growth regulators increase susceptibility
• Higher nitrogen (N) rates may speed up plant growth
• Planting date
• Favorable growing conditions (temperature and soil moisture)
• Plant size affecting wind resistance
  • Leaf area
  • Leaf orientation
  • Row direction

References:

¹ Elmore, R. and R. Ferguson. 1999. Mid-season stalk breakage in corn: hybrid and environmental factors. Journal Series No. 12188. J. Prod. Ag. 12:293-299.

² Elmore, R. 2011. Wind and corn. ICM News. Iowa State University. https://crops.extension.iastate.edu/cropnews/2011/07/wind-and-corn