WHAT TO DO ABOUT PURPLE NUTSEDGE (NUTGRASS)
1. Get the Correct Information
After 38 years, our owner (a Pest Control Advisor) has never heard of a single person who has had success with digging and screening the nuts from the soil. Don’t try it; it does not work. In fact picking nutgrass increases the viability of the other dormant tubers (i.e. nutlets) in the soil.
The vast majority of nutgrass in Kern County is purple nutsedge, not yellow. More than 90% of the nutgrass does not come from seed, which makes mower contamination nearly impossible. Nutgrass spreads rapidly, producing between 4 and 12 million tubers per acre. In fact, a single tuber can form 1,900 plants and 6,900 other tubers after just one season.*
2. PROPER HERBICIDE APPLICATION
High Yield Nutgrass Killer™ and Prosedge™ contain an herbicide that will control purple nutsedge. It must be applied with a non-ionic surfactant. Additives such as dish soap will not work. In fact, they can decrease the effectiveness of the product. Once you mix High Yield™ or ProSedge™, it must be used within 12-24 hours. You must shake the solution for 2 minutes before spraying. You must also shake every few minutes to keep the herbicide from settling.
Spraying glyphosate (RoundUp™) on nutgrass will only kill surrounding vegetation, eliminating any competition, and potentially making the problem worse.
3. BE AWARE OF POSSIBLE CONTAMINATION
A University of Santa Barbara study showed that when nutgrass was put in a compost heap for two weeks, with high enough temperatures to kill all other weeds, that the tubers were still able to grow even after this extreme “cooking” process. This means that nutgrass is in contaminated nursery stock soil, steer manure, organic materials, and even bagged soil or sand. Because of this, it is very important to use the proper materials. Also know that tilling, renovating, or power raking a lawn can cause small infestations to become more problematic.
* Biology and Management of Nutsedge, Jodie S. Holt, Dept. of Botany and Plant Sciences, University of California, Riverside, CA 92521.