Growth and development of wild oat (Avena fatua L.)

Wild oat is an invasive and economically important weedy species in the Red River Valley of Minnesota and North Dakota. Understanding wild oat emergence, growth, development and control are needed for optimum and consistent control of wild oat. Research plots were established at Crookston, MN and Fargo, ND to evaluate the emergence, growth and development, and control of wild oat. Wild oat emergence was correlated with growing degree days (GDD) and hydrothermal time (HTT) but not calendar days. A Weibull function was fitted to cumulative wild oat emergence and GDD and HTT. These models closely fit observed wild oat emergence patterns. This model is the first to use HTT to predict wild oat emergence under field conditions. Wild oat plants that emerged early in the growing season had a greater biomass, more seed production, were taller and had more leaves, tillers, and required more time for flag leaf emergence and heading compared to wild oat plants that emerged later in the season. Even though early emerging wild oat plants are potentially more competitive, later emerging wild oat plants have the potential to produce seed and if left uncontrolled, will continue to contribute to the seed bank. Reduced rates were as profitable, or more profitable, than 1X labeled rates of the herbicides investigated. At both locations and years and with both wheat and barley, there was no a consistent relationship among wild oat herbicide or rate investigated. Visual wheat and barley injury was minimal with all herbicide applications at both locations and years. Although there were differences between visual wild oat control, biomass reduction, crop yield, and net economic return (NET) of individual herbicide applications, reduced rates did not consistently give less wild oat control or NET compared to 1X rates. In some cases the 1/2X herbicide rate resulted in a greater NET compared to the 3/4 and 1X rates. These findings will assist farmers and agricultural professionals with planning timely and more accurate control of wild oat.