By Peter Thomison, Corn production specialist
Ohio State University

Strong winds and heavy rains associated with severe thunderstorms can lodge or knock corn plants over, especially if the nodal root system is not fully developed. The persistent rains we've experienced across much of Ohio since planting may also result in shallow root systems that are more vulnerable to wind lodging. Root lodging can be directly related to severe feeding by rootworm larvae.

However, Bt rootworm resistance alone will not prevent root lodging. Hybrids differ in their ability to resist root lodging. Moreover, a hybrid may exhibit outstanding stalk lodging resistance but may be very susceptible to root lodging. Hot, dry weather conditions and soil compaction may inhibit nodal root formation and predispose plants to wind injury.

Strong winds can pull corn roots part way out of the soil. The problem is more pronounced when soil are saturated by heavy rains accompanying winds. If root lodging occurs before grain fill, plants usually recover at least partly by "kneeing up." This response results in the characteristic gooseneck bend in the lower stalk with brace roots providing above ground support. If this stalk bending takes place before pollination, there may be little effect on yield. When lodging occurs later in the season, some yield decrease due to partial loss of root activity and reduced light interception may occur. If root lodging occurs shortly before or during pollen shed and pollination, it may interfere with effective fertilization thereby reducing kernel set. Several university studies have been performed to assess the impact of wind lodging on corn growth and grain yield.

Iowa State University researchers forced V10 corn to "root lodge" at a 45-degree angle in plots with and without rootworms. Grain yield of root-lodged corn without rootworms yielded 11-percent and 40-percent less than the control in the two years of the study, while root-lodged corn with rootworms yielded 12-percent and 28-percent of the control. Years were a major factor affecting the yield response.

The ISU researchers concluded that "root lodging was more detrimental to biomass accumulation and grain yield than corn rootworm injury caused by larval feeding." In another ISU study that evaluated natural root lodging, root lodged plants intercepted 28-percent less light than plants that were not root lodged.

In a University of Wisconsin study, root lodging was simulated by saturating soil with water and manually pushing corn plants over at the base, perpendicular to row direction. Wind damage was simulated at various vegetative stages through silking (V10 to R1). Compared to hand-harvested grain yields of control plants, grain yield decreased by 2% to 6%, 5% to 15% and 13% to 31% when the lodging occurred at early (V10-V12), mid (V13-V15) and late (V17-R1) stages, respectively.

SOURCE: Ohio State University.