Posted 20 September 2011. PMN Crop News.
Producers Should Check Grain Sorghum for Stalk Rot
Source: Kansas State University Press Release. www.ag.ksu.edu
Manhattan, Kansas (September 9, 2011)--A lot of attention has been given to stalk rot and other lodging problems in corn this year. But producers should keep in mind that stalk rot can be an even bigger problem in grain sorghum due to a generally thinner stalk, said Doug Jardine, K-State Research and Extension plant pathologist.
The best estimates are that at least 5 percent of the sorghum crop is lost each year to stalk rot, he said.
“The incidence of stalk rot in individual fields may reach 90 to 100 percent with yield losses of 50 percent. The most obvious losses occur when plants lodge. More important may be the yield losses that go unnoticed,” Jardine said.
These losses are caused by reduced head size, poor filling of grain, and early head lodging as plants mature early, he explained.
In grain sorghum, the two most common types of stalk rot are charcoal rot and Fusarium stalk rot, he said. Although caused by many different organisms, the symptoms of the various stalk rots are somewhat similar, he said.
“Symptoms generally appear several weeks after pollination when the plant appears to prematurely ripen. The leaves become dry, taking on a grayish-green appearance similar to frost injury. The stalk usually dies a few weeks later,” Jardine said.
Producers can check their sorghum for stalk rots by squeezing the lower stem with their thumb and fingers.
“If the stalks crush easily, they are probably infected with one of the stalk rot organisms and may lodge at any time. Check 100 plants across the field to determine the percentage of affected plants. If the percentage of stalk-rot-infected plants is high, sorghum should be harvested as soon as possible, even if it hasn’t dried down adequately in the field,” the K-State plant pathologist said.
“If the stalks are firm, the plants will probably be able to stand just fine in the field for several more weeks if necessary,” he added.
Stalk rot is a stress-related disease, he said.
“When the carbohydrates used to fill grain become unavailable due to nutrient shortage, drought stress, leaf loss from insects, hail, disease or reduced sunlight, the plant is forced to use nitrogen and carbohydrate reserves stored in the stalk to complete grain fill. This loss of nitrogen and carbohydrate reserves weakens stalk tissues and results in increased stalk rot susceptibility,” Jardine said.