CORESTA Meeting, Agronomy/Phytopathology, 2023, Cancun, APPOST 03

Flutriafol residues in non-traditional Burley tobacco

North Carolina State University, Department of Crop & Soil Sciences, Raleigh, NC, U.S.A.

Flutriafol is a fungicide that is not currently labelled for tobacco production, which may offer suppression of common foliar leaf spot diseases such as target spot (Rhizoctonia solani) and frogeye leaf spot (Cercospora nicotianae). In spite of such promise for disease suppression, the cured leaf residues resulting from flutriafol application in Burley tobacco have not been reported. Field trials that serve to quantify agrochemical residues for two experimental fungicides applied to field grown Burley tobacco were conducted in North Carolina from 2019 through 2021. Across these growing seasons, Burley tobacco treated with flutriafol (Topguard® at 1.02 L/ha/application; 128 g ai/ha/application) or a premix combination of azoxystrobin + flutriafol (Topguard® EQ at 0.58 L/ha; 173 g azoxystobin + 128 g flutriafol/ha/application) was evaluated in one growing environment within each season. Both agrochemicals were applied twice, once at layby (36-49 days after transplanting) and again 30 days before harvest. Residue results varied across growing seasons. In 2019, flutriafol residues from Topguard® were highest in lower stalk samples (9.73 mg/kg) but declined in middle and upper stalk samples (5.75 and 4.85 mg/kg, respectively). In contrast, flutriafol residues were similar between lower and middle stalk samples in 2020 (1.63 and 1.50 mg/kg, respectively) and 2021 (1.40 and 1.17 mg/kg, respectively). Within the same two seasons, flutriafol residues were lowest in upper stalk samples (1.13 and 0.53 mg/kg, respectively). When Topguard® EQ was applied, flutriafol residues were similar across all stalk positions in 2019 but generally demonstrated a reduction from lower to upper stalk positions in 2020 and 2021. Azoxystrobin residues were similar across stalk positions and were consistently less than 2.5 mg/kg. Our results provide cured leaf residue guidance relative to these fungicides, should they be approved for application in the commercial production of Burley tobacco.