Effectiveness of organic and reduced risk herbicides on lawns and playing fields. A. Senesac*¹, J. Kao-Kniffin²; ¹Long Island Horticultural Research & Extension Center, Riverhead, NY, ²Cornell University, Ithaca, NY.

 

Starting in 2011, schools and daycare centers in New York State were banned from using conventional pesticides on playing fields, lawns, and playgrounds. The NYS Child Safe Playing Fields Law, enacted to minimize pesticide exposure to children, restricts the use of pesticides to minimal risk ingredients that include clove oil, lemongrass oil, cinnamon oil, and other compounds listed under FIFRA 25(b). Many of the allowable pesticides are approved as organic products through the Organic Materials Review Institute (OMRI), yet few of the products have been tested for efficacy in turfgrass settings. The trial was conducted in weedy Kentucky bluegrass plots infested with Taraxacum officinale, Trifolium repens, Plantago lanceolata, Glechoma hederacea, and Artemisia vulgaris. Three of the treatments were organic herbicides (GreenMatch EX, Weed Zap, and Burnout II) that are allowable for use in schools and daycare centers. Two treatments were reduced risk herbicides (Fiesta and Ecosense Weed B Gone) that require one-time application approval from the local school board, NYS Department of Health, or NYS Department of Environmental Conservation. And one treatment was a thermal propane-fueled torch. Treatments were applied in June and July, biomass of harvested plants was measured, and percent cover of turfgrass and select weeds was evaluated. The fresh weight data collected two weeks after the first application indicated that broadleaf weeds were significantly reduced by most of the treatments. Grass weeds were reduced somewhat but not as significantly. However, after the second application, Fiesta, Ecosense, and BurnOut II were the only spray treatments that caused significant reductions in broadleaf weed fresh weight. More research is needed to determine if combining some of the better products would result in additive levels of control. A follow up study was conducted in the greenhouse with seedling tall fescue, Ambrosia artemisiifolia, and Glechoma hederacea.  Treatments included Adios, Avenger, Fiesta, Weed Zap, Burnout II, and GreenMatch EX.  Avenger resulted in the greatest injury to the seedling tall fescue.  Adios, Avenger, Weed Zap, Burnout II, and GreenMatch EX provided excellent control of the Ambrosia artemisiifolia. Avenger, Burnout II and GreenMatch EX provided acceptable control of Glechoma hederacea. Corresponding author: jtk57@cornell.edu