48th TWC, Tob. Work. Conf., 2018, abstr. 43

Performance of fungicides and varietal resistance for the management of Black Shank in the southern Maryland region

BEALE B.
University of Maryland, Leonardtown MD USA

A field trial was conducted for two years during the 2015 and 2016 growing season in a field with high levels of black shank (Phytophthora parasiticia). The 2015 study examined the effect of Ridomil Gold (mefenoxam) and Presidio (fluopicolide) treatment regimens on black shank incidence across a susceptible (KY 14xL8LC) and a resistant variety (KT 209LC). The 2016 trial examined the effect of Orondis (oxathiapiprolin + mefenoxam), Presidio and Ridomil Gold treatment regimens on black shank incidence across a susceptible (KY 14xL8LC) and a resistant variety (HB4488PLC). Fungicides were applied as a simulated transplant water (TPW) treatment and/or at first cultivation (1st C) and/or at layby (LBY). Trials were replicated five times in 2015 and four times in 2016 using a randomized complete block designed. Results of the susceptible variety 2015 trial indicated any treatment containing Presidio in TPW provided significantly better control than treatments with Ridomil or the untreated control (UTC). There were no infected plants in the 2015 trial in the resistant variety. In 2016, the Presidio TPW treatments were removed and Orondis included. Results of the susceptible variety 2016 trial indicated treatments with Orondis (TPW only) or Orondis (TPW) + Presidio (LBY) provided better control than other treatments. The treatment of Presidio applied at second cultivation was no better than the UTC. As in 2015, there were no infected plants in the 2016 trial in the resistant variety. In summary, selection of cultivars with resistance to Race 1 is critical for fields with heavy black shank pressure. Treatments with Orondis in the transplant water performed the best in reducing the total percentage of plants affected and well as delaying the onset of symptoms. (Reprinted with permission)