|
Channel Field Check Up
KAYLISSA HALTER
ROBINSON, ILL.
Southern Illinois, along with much of the Midwest, received tremendous rainfall the past month creating the perfect environment for disease development. Proper diagnosis of soybean diseases is essential because management options vary among diseases. However, common soybean diseases can share some similar characteristics and often be confused with one another.
Sudden Death Syndrome
Sudden death syndrome (SDS) is caused by the fungus Fusarium virguliforme. It tends to occur in high-yielding soybean crops after bloom. The potential yield losses can vary due to timing of disease development. SDS is most severe on soybeans planted early in cool, wet soils that are then hit by midsummer rains that saturate the soil. Some management practices can help reduce the risk of SDS damage, but will not prevent the disease. Check with your Channel seedsman or local agronomist for recommendations on how to manage SDS.
Stem Canker
Stem canker is caused by Diaporthe phaseolorum var. caulivora in the northern U.S. and D. phaseolorum var. meridionalis in the southern U.S. Visual symptoms may occur in late vegetative to early reproductive stages, and begin as small reddish-brown lesions at the base of branches or petioles. The lesions elongate and turn dark brown to black, become sunken and often girdle the stems. Lesions typically occur around the fourth or fifth node or in the region of the second and third trifoliate leaves. Yield losses from stem canker can be as high as 50 to 80 percent. The fungus overwinters in residue, soil or infected seed and infects soybean plants when wet weather and warm temperatures combine.
Several methods can help to manage the risk of stem canker:
• Bury infected crop residue after harvest when possible
• Rotate with another crop for one to two years
• Plant resistant soybean products
• Fungicides on seed can prevent introduction of the fungus, but cannot control existing field infections
Brown Stem Rot
Brown stem rot (BSR) is caused by two genotypes of Phialophora gregata (syn. Cadophora gregata). It can be difficult to recognize before pod set due to lack of early external symptoms. When symptoms do appear, they may be expressed in two ways: only internal vascular browning or vascular browning with leaf chlorosis and necrosis. The fungus that causes BSR survives in crop debris and soil to a depth of 1 foot. Infection occurs early in the growing season through main and lateral roots and moves into the lower stem, then upward through vascular channels. Foliar fungicides do not have an effect on BSR. Some management practices are:
• Grow soybeans in the same field only once every three or four years
• Plant resistant soybean products
• Because the risk tends to be higher with a soil pH of less than 6.5, maintain soil pH at 7.3 ∆
KAYLISSA HALTER: Channel Agronomist
|
|