Greensnap versus Root Lodging in Corn

Richard Taylor, Extension Agronomy Specialist; rtaylor@udel.edu

With the possibility that the remnants of tropical storm Bill will arrive in the MidAtlantic region this weekend, there’s a chance of either high winds or some straight-line winds in thunderstorms. Many of the corn fields in Delaware have recently received sidedress nitrogen (N) and have reached the rapid growth phase in corn development. This may mean that at least some fields will be at risk for greensnap or storm induced breakage. Hybrids differ in their susceptibility to greensnap and the stage of development also influences the risk of this type of wind injury. Corn in the V10 to V12 (10 to 12 leaf collars fully emerged and visible) is most at risk. Although this problem is more often seen in MidWest corn fields where the prevalence of high winds is greater, the remnants of tropical storm Bill could easily create the same conditions for us over the coming weekend. Although not common in the MidAtlantic, we did observe greensnap last year in the 2014 Corn Hybrid Performance Trials, especially in the Marydel, Delaware location.

Greensnap can be distinguished from root lodging in that the breakage occurs at a stem node. The upper portion of the corn plant can be completely severed from the lower stem and root or can remain partially attached, although in all the cases I’ve observed in Delaware the impact on yield is almost a total loss. Plants can break anywhere along the stem although it most often occurs below the node where the ear will form. For root lodging, large sections of a field or perhaps individual plants will be pushed over by the winds but the stalks do not break. Root lodging often is associated with heavy rainfall, higher winds, and will be worse where corn root worms or cultivation has clipped some of the roots that help support the plant. If it occurs before tasseling, the plant often produces new brace or adventitious roots at the nodes close to or in contact with the soil surface and the new growth begins to turn upright again. Although root lodging can cause harvest problems, its impact on yield potential is often minimal compared with greensnap.

Growers will ask whether there’s anything they can do to prevent greensnap and unfortunately the answer is that other than choosing a hybrid that’s resistant to greensnap there’s nothing a grower can do about the situation. Since the condition only occurs on rare occasion in our region, most of the hybrids available to growers may not have greensnap ratings and even with such ratings other characteristics such as yield potential, gray leaf spot resistance, etc. are more important to our growers than greensnap resistance.

After the storms pass, growers should observe their fields for evidence of greensnap; and, if present, estimate the severity of the problem since this estimate will likely correspond to a potential loss estimate. Estimates of loss from root lodging where the plant tries to resume vertical growth vary greatly depending on how early the damage occurs and the growing conditions for the rest of the season.

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