Baseline sensitivity of Cercospora zeae-maydis to quinone outside inhibitor fungicides

C. A. Bradley, D. K. Pedersen

Research output: Contribution to journalArticlepeer-review

28 Scopus citations


Cercospora zeae-maydis, the causal agent of gray leaf spot on corn (Zea mays), can cause severe yield loss in the United States. Quinone outside inhibitor (QoI) fungicides are effective tools that can be used to manage gray leaf spot, and their use has increased in corn production in the United States. In total, 61 C. zeae-maydis isolates collected from fields in which QoI fungicides had never been applied were tested in vitro using azoxystrobin-, pyraclostrobin-, or trifloxystrobin-amended medium to determine the effective fungicide concentration at which 50% of the conidial germination was inhibited (EC50). The effect of salicylhydroxamic acid (SHAM) also was evaluated for seven isolates to determine whether C. zeae-maydis is capable of using alternative respiration in azoxystrobin-amended medium. All seven C. zeae-maydis isolates tested had significantly greater (P < 0.02) EC 50 values when SHAM was not included in medium amended with azoxystrobin, indicating that C. zeae-maydis has the potential to utilize alternative respiration to overcome QoI fungicide inhibition in vitro. Baseline EC50 values of azoxystrobin ranged from 0.003 to 0.031 μg/ml, with mean and median values of 0.018 and 0.019 ug/ml, respectively. Baseline EC 50 values of pyraclostrobin ranged from 0.0003 to 0.0025 μg/ml, with mean and median values of 0.0010 and 0.0010 μg/ml, respectively. Baseline EC50 values of trifloxystrobin ranged from 0.0004 to 0.0034 μg/ml, with mean and median values of 0.0023 and 0.0024 μg/ml, respectively. These baseline sensitivity values will be used in a fungicide resistance monitoring program to determine whether shifts in sensitivity to QoI fungicides are occurring in C. zeae-maydis populations.

Original languageEnglish
Pages (from-to)189-194
Number of pages6
JournalPlant Disease
Issue number2
StatePublished - Feb 2011

ASJC Scopus subject areas

  • Agronomy and Crop Science
  • Plant Science


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