Influence of fungicide selection and application timing on take-all root rot management under field and greenhouse conditions

Take-all root rot (TARR) is a detrimental disease of ultradwarf bermudagrass (Cynodon dactylon x Cynodon transvaalensis; UDB) putting greens frequently diagnosed where warm-season grasses are grown. Since this disease is largely aggregated and variable under field conditions, field research is difficult and often yields inconsistent results. Multiple pathogens have only recently been associated with this disease, so practical management solutions such as fungicide efficacy and fungicide application timing have not been thoroughly investigated. Therefore, the objectives of this research were to determine the influence of fungicide selection and fungicide application timing on take-all root rot management under field and greenhouse conditions. In general, fungicides from the quinone outside inhibitor and/or demethylation inhibitor chemical classes provided the greatest reduction in take-all root rot severity. Fungicide applications that were made when soil temperatures were between 77-86 degrees F provided the greatest disease suppression. The in vivo greenhouse method developed in this research proved to be an efficient and consistent method to evaluate management practices such as fungicide efficacy on take-all root rot. This research improves our understanding of fungicide efficacy and fungicide application timing for take-all root rot management on ultradwarf bermudagrass. Fungicides from the QoI and/or DMI chemical class provided the greatest reduction in take-all root rot severity. Apply fungicides when the 5-day average soil temperature at a 2-inch depth is approximately 80 degrees F for TARR management. The in vivo screening method developed here is an efficient way to evaluate TARR management parameters.