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Frost injury symptoms can include necrotic splotching to overall grayish-blackening of leaf tissue. Plants appear wilted and, if completely frozen, leaflets dry and drop off and plants cease growth.
Because soybean vegetative tissue can tolerate temperature down to 27F for several hours without harm, examine damaged plants carefully though dissection. When all above ground tissue, including terminal and axillary buds, are damaged (tissue turns brown), replanting is required. Oftentimes, only upper leaves, but not the growing point, are damaged and growth will resume. Regrowth from axillary buds may occur if the terminal bud is killed. Late in the season, a killing frost prior to plant maturity can reduce yield and quality through reduced seed size and/or green seed. Especially in the southern U.S. or with varieties in the North containing southern gemplasm, several consecutive nights with temperatures below 50F can result in lower yields due to reduced metabolic activity. Symptoms may include bronzing or blackening of leaves and smaller seed. |