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POSTERS: Chemical control

Impact of metalaxyl, ethaboxam, and mefenoxam on in-vitro growth rate of Pythium isolates from Pennsylvania.
Ananda Bandara - The Pennsylvania State University. Paul Esker- The Pennsylvania State University, Dilooshi K. Weerasooriya- The Pennsylvania State University, Brandon Wilt- The Pennsylvania State University

Pythium species are among the most important soil borne pathogens that can limit the yields of many economically important crops. Fungicide seed treatments are widely used to control these pathogens. Selection of appropriate fungicides with proper concentration is pivotal for efficient control. The goal of this study was to determine the efficacy of selected fungicide active ingredients on in-vitro growth of Pythium isolates obtained from Pennsylvania. One hundred and fifty-three putative Pythium isolates were recovered from soil samples collected from 7 counties using selective medium P5ARP. Each isolate was grown in PDA amended with 0, 10, 100, and 1000 ppm concentrations of Metalaxyl, Ethaboxam and Mefanoxam. Colony diameter was measured at different time points to compute the colony growth rate. Analysis of variance showed significant isolate × concentration interaction for all tested fungicides. Among tested isolates, 70.6%, 88.2% and 64.7% were insensitive (non-significant growth rate difference compared to counterpart control = 0 ppm) to Metalaxyl, Ethaboxam and Mefanoxam respectively. 13.1%, 4.6% and 9.8% of the isolates were respectively sensitive to Metalaxyl, Ethaboxam and Mefanoxam only at 1000 ppm. Findings showed that the majority of the tested isolates were unaffected by the different fungicide active ingredients even at higher concentrations and that they cannot be used as an efficient means (i.e. seed treatments) of preventing yield losses.