Efficacy and Application Methods of Oxathiapiprolin for Management of Black Shank on Tobacco.

Black shank, caused by Phytophthora nicotianae, is responsible for serious yield and quality reduction in tobacco production. Application of effective fungicides continues to be a viable component in developing integrated disease management programs. Experiments were conducted in 2011 to 2013 to determine the efficacy and application methods of a new fungicide, Zorvec (a.i. oxathiapiprolin), for management of black shank under field conditions. Oxathiapiprolin is the first member of a new class of isoxazoline fungicide. Application of Zorvec (0.35 liter/ha) onto tobacco seedlings 1 week prior to transplanting in conjunction with directed applications of the product at 0.7 liter/ha at first cultivation and lay-by (last cultivation) reduced black shank significantly compared to the nontreated control in the experiments conducted in 2011 and 2012. Application of Zorvec at 1.4 liter/ha through transplant water followed by directed sprays at first cultivation and lay-by at 0.7 liter/ha reduced black shank significantly compared with the nontreated control in 2012 and 2013 studies. These treatments were not significantly different (P = 0.05) in disease reduction compared to mefenoxam. All treatments involving Zorvec increased tobacco yield significantly (P = 0.05) or showed a tendency to increase tobacco yield over the nontreated control in all experiments conducted in 2011 to 2013. The results indicated that the new fungicide oxathiapiprolin was effective in reduction of P. nicotianae on tobacco.