Submitted to: North Central Weed Science Society US Proceedings
Publication Type: Abstract only
Publication Acceptance Date: 12/18/2001
Publication Date: N/A
Citation: Interpretive Summary:
Technical Abstract: Plant growth regulator (PGR) herbicides are widely used in corn production. However, soybeans are very sensitive to these herbicides. Symptoms resembling growth regulator injury are commonly reported during the growing season; there are various ways that a soybean crop can come in contact with a PGR herbicide. Often, it is difficult to trace abnormal foliar symptoms to a PGR herbicide exposure; other stresses such as soybean viruses can cause similar symptoms. There are no diagnostic tools available to determine if symptoms are due to PGR herbicide exposure or some other source. Field studies were conducted to characterize the effects of PGR herbicides on soybeans. Laboratory experiments are underway to develop a diagnostic assay to identify or rule out PGR herbicides as the causal agent of abnormal foliar symptoms. These experiments include various PGR and other herbicides. The herbicides were applied at two very low rates that might be unintentionally applied to soybeans. They were applied at early vegetative (V2), late vegetative (V6) and early reproductive (R2) stages. The herbicides caused varying levels of injury to soybeans, affecting plant height, leaf area and date of maturity. Only the most severe injury resulted in reduced yield. Soybeans are more sensitive to dicamba than clopyralid, and more sensitive to clopyralid than 2,4-D. There were differences in foliar symptoms among the PGR herbicides that may aid in identifying them as the cause of injury.