Reducing Topramezone Injury to Bermudagrass Utilizing Micronutrients

Abstract

Bermudagrass (Cynodon dactylon L. Pers.) is one of the most common turfgrass species planted throughout the United States on golf courses, home lawns, and sports fields. Bermudagrass is able to tolerate a wide variety of environmental conditions; however, weeds can rapidly invade turfgrass areas weakened due to drought, disease, insect infestation, or mechanical damage. Grassy weeds such as goosegrass (Eleusine indica L. Gaertn.) and crabgrass (Digitaria spp.) often fill these voids and control can be problematic once established. Post-emergent control options of goosegrass and other grassy weeds continue to decline due to regulatory pressure and herbicide resistance. Previous research demonstrates that topramezone offers excellent control of goosegrass, crabgrass, and other weed species, and potentially could be a viable control option; however, injury to bermudagrass may be unacceptable. Topramezone safening research on bermudagrass is lacking. Multiple greenhouse, field, and growth chamber studies were performed from 2015 to 2020 in Auburn, AL. The objectives of these studies were to 1) evaluate various additives to determine whether bermudagrass bleaching injury was reduced; 2) determine whether iron application timings or different formulations of iron had an overall reduction effect; 3) assess other micronutrients for bleaching symptomology reduction; and 4) evaluate the effect that seasonal daylength and temperature have on chlorophyll and carotenoid production following topramezone application to bermudagrass. Data indicated that bermudagrass treated with a combination of topramezone and iron sulfate, chelated iron (DTPA), or zinc sulfate produced greatest reduction of bleaching symptomology out of all of additives tested. Furthermore, topramezone combinations that included nitrogen (N), whether alone or in combination with a nutrient product, often increased overall observed bleaching of bermudagrass. The addition of chelated iron, iron sulfate, or zinc sulfate safened the application of topramezone on bermudagrass. These findings should be communicated with turfgrass managers to help alleviate their concerns with use of this product, while also offering another mode of action to combat herbicide resistance.