Utilization of Zinc Sulfate for Poa Annua Control.

Poa annua L., annual bluegrass, is one of the most problematic weeds in turfgrass. Due to variability in herbicide efficacy, an integration of cultural control practices could lead to improved weed control. Zinc is often applied due to plant nutrient deficiencies. Initial research indicates that applying zinc at rates above the required micronutrient level reduces P. annua emergence. The goal of this research was to evaluate P. annua control following zinc applications in non-overseeded bermudagrass. A field study was conducted in 2009 and 2010 at the Turfgrass Research Unit in Auburn, AL. The study was a randomized complete block design, with three replicates, conducted on a non-overseeded bermudagrass putting green. Treatments included four zinc rates (22.4, 44.8, 89.6, 179.2 kg Zn ha^-1), single and multiple applications of fenarimol (2.24 kg ai ha^-1), fenarimol + Zn (22.4 and 89.6 kg Zn ha^-1), and prodiamine (1.12 kg ai ha^-1). Initial treatments were applied in mid-September. P. annua percent control was evaluated throughout the fall and winter. Final ratings included individual plant counts. Data was transformed to percent control relative to the non-treated. Data was analyzed using Proc GLM in SAS, and means were separated using Fisher’s Protected LSD (P=0.05). Zinc applied at 179.2 kg Zn ha^-1 controlled P. annua 70-80% throughout the season. Prodiamine, which is currently not labeled for putting greens, provided 90% control. Fenarimol applications only controlled P. annua 40-50%. These data suggest that by applying zinc at rates of 89.6-179.2 kg Zn ha^-1, it is possible to reduce P. annua populations in a non-overseeded bermudagrass putting green.