Poster: Biology & Disease Mgmt: Chemical Control
Fungicide sensitivity of Pythium species from the North Central Region of the United States
R. MATTHIESEN (1), A. Robertson (1), M. Chilvers (2) (1) Iowa State University, U.S.A.; (2) Michigan State University, U.S.A.
Pre- and post-emergence damping-off of soybean in the North Central Region (NCR) can be caused by several Pythium spp. Various fungicide seed treatments are used to manage damping-off. Little is known about the effect of temperature on fungicide sensitivity of Pythium spp. in the NCR. The goal of this study was to assess fungicide sensitivity of Pythium spp. from the NCR to metalaxyl, ethaboxam, and azoxystrobin by assessing mycelial inhibition in vitro at two temperatures. Isolates of four Pythium spp. (P. lutarium, P. oopapillum, P. sylvaticum, and P. torulosum) from the Midwest, collected through the USDA funded Oomycete Extension Network, were assessed for fungicide sensitivity using five concentrations (0, 0.1, 1.0, 10, and 100 μg a.i./ml) at 13°C and 23°C in an agar medium plate assay. All species from all states, except AR, were more sensitive (>50% mycelia inhibition) to metalaxyl and ethaboxam than to azoxystrobin. At 13°C isolates of P. oopapillum from all states, except AR, were less sensitive to all fungicides compared to 23°C. Isolates of P. sylvaticum from IA, ND, NE, SD, and WI were less sensitive to all fungicides at 23°C compared to 13°C. At 13°C isolates of P. torulosum from IA, IN, ND, NE, and WI were less sensitive to all fungicides tested compared to 23°C. An improved understanding of fungicide sensitivity of Pythium spp. could improve our ability to develop and implement effective fungicide seed treatments in the NCR.