Spring is arriving and leaving soon, much quicker than last year. Proper timing of pre-emergence herbicides is critical to successfully suppressing summer annual grasses like goosegrass, foxtail and crabgrass. These grasses need the proper soil temperature and soil moisture to germinate and establish. Eighty percent of the germination will occur when the 0-2 inch depth soil temperature is consistently reaching 60-70 degrees F. Pre-emergence herbicides need to be applied before the soils reach this optimum range. The herbicide that we have found to be most useful is called Pendulum. This herbicide has a yellow color to it that will stain white shoes and pants. We will begin spraying this on the rough this week. We will continue the application throughout the next two weeks as we will use the timing of rain or irrigation to water it into the soil.
A tool that we use to help determine when it is the best time to spray is Growing Degree Days. Growing Degree Day (GDD) is a method to track the heat units that have accumulated and are needed for plant growth and development. A website that we use to track GDD is gddtracker.net created by Dr. Ron Calhoun. Using this website and data from our weather station we know that soon will be the optimum time to apply our pre-emergent herbicide and get the most effectiveness from it. The target range for this model attempts to predict when the 0-2 inch depth soil temperatures consistently reach 50-55 degrees F and therefore provided adequate time for the pre-emergence herbicide to be incorporated before germination occurs. If we decided to apply it any sooner to accommodate golf there would lose some of it’s efficacy in suppressing weeds.
Please advise all staff, members, and guests of the applications being made and the risk of staining clothing and shoes while in the rough. If there are any questions or concerns regarding this procedure please reference this email. Thank you.