herbicide resistance

For many landscapers, the arrival of the busy Spring season is a chance to achieve improvements and efficiencies over last year’s practices. In a turfgrass context, it could mean mapping better routes to visit a group of properties, or outlining the top five reasons for customer call-backs last year. Each January, our team in the University of Tennessee Plant Sciences Department meets to discuss what we learned in the previous season working with turfgrass managers on weed control issues. Essentially, the items brought forward are those that rose to the top in the midst of hundreds of different research trials, thousands of treatments, and many different weed species. This article provides an outline of what we learned in 2019 in the hopes that it will be useful in 2020. Climate Curveballs Abnormalities in climate are becoming more common and 2019 was no exception. For example, it only took the first 12 weeks of 2019 for rainfall accumulation in Knoxville, TN to equal 50% of the entire yearly average. This affected winter annual weed management programs, particularly in warm-season lawns, and made the process of initiating spring preemergence (PRE) herbicide programs difficult. Additionally, the summer stress period that many cool-season lawns face each season was longer than ever before in 2019. Air temperature in our area during September, a month many consider to be the beginning of Autumn, was no different than June, July, or August last year. The 90-day period of Summer stress that cool-season lawns typically endure was extended ...