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Title: INFLUENCE OF HERBICIDES ON RHIZOCTONIA ROOT AND HYPOCOTYL ROT OF SOYBEAN

Author
item BRADLEY, CARL - UNIV OF ILLINOIS
item HARTMAN, GLEN
item WAX, LOYD
item PEDERSEN, WAYNE - UNIV OF ILLINOIS

Submitted to: Crop Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/14/2002
Publication Date: N/A
Citation: N/A

Interpretive Summary: Rhizoctonia root and hypocotyl rot is a common disease of soybean that causes major problems in some areas of soybean production almost every year, varying with the weather and other conditions. Field observations by researchers and growers seemed to indicate a possible interaction between injury from herbicides and presence of this disease. We established field studies to determine how soil and foliarly applied herbicides affect the severity of Rhizoctonia root and hypocotyl rot on the growth and yield of several soybean cultivars. The work was done over a two year period at three locations in Illinois under various weather conditions. We found that in general herbicides did not significantly decrease the R. solani disease severity index (DSI) compared to the control plots. However, there were some increases in DSI compared to the control at a low frequency in some years. In greenhouse studies, the herbicides dimethenamid plus metribuzin, pendimethalin, acifluorfen, and imazethapyr caused an increase in Rhizoctonia root and hypocotyl rot severity compared to the no-herbicide control. These investigations demonstrated the potential for some herbicides to increase the severity of Rhizoctonia on soybean in some circumstances, especially where herbicides caused injury to the crop and the applications were followed by adverse weather that allowed the combined stresses to interact. These findings are important to those planning future research on herbicide x disease interactions and to those who are preparing and distributing guidelines for soybean production and protection.

Technical Abstract: Rhizoctonia root and hypocotyl rot, caused by Rhizoctonia solani, is a common disease of soybean. Field studies established to observe how preemergence and postemergence herbicides affect the severity of Rhizoctonia root and hypocotyl rot on several soybean cultivars were conducted in Champaign, Dekalb, Monmouth, and Urbana, Illinois. Herbicides did not significantly (P 0.05) decrease the R. solani disease severity index (DSI) compared to the control, but did cause some increases in DSI compared to the control at a low frequency in some years. In greenhouse studies, dimethenamid + metribuzin, pendimethalin, acifluorfen, and imazethapyr caused an increased Rhizoctonia root and hypocotyl rot severity compared to the no-herbicide control.