Open AccessIdentification of Resistance to Multiple Fungicides in Field Populations of Venturia inaequalis
Author(s) -
Kimberly Sue Chapman,
George W. Sundin,
Janna L. Beckerman
Publication year - 2011
Publication title -
plant disease
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.663
H-Index - 108
eISSN - 1943-7692
pISSN - 0191-2917
DOI - 10.1094/pdis-12-10-0899
Subject(s) - fungicide , venturia inaequalis , myclobutanil , biology , apple scab , horticulture , mycelium , spore , botany
Venturia inaequalis, the causal agent of apple scab, is controlled primarily by fungicides. Long-term, extensive fungicide use has led to the development of resistance to multiple fungicides. To assess fungicide resistance, isolates of V. inaequalis were collected from Indiana and Michigan orchards. Single-spore derived isolates were evaluated by mycelium growth assays with previously determined discriminatory doses on media containing dodine, kresoxim-methyl, myclobutanil, or thiophanate-methyl. Of 195 isolates tested, 5.2, 0.7, 57.0, and 92.6% of isolates were found to be resistant to dodine, kresoxim-methyl, myclobutanil, and thiophanate-methyl, respectively. This is the first report of kresoxim-methyl field resistance in these states. Isolates resistant or shifted to a single fungicide were often found to have multiple fungicide resistance. Of all isolates tested, 38% were identified as resistant or shifted to two fungicides, and 12% were resistant or shifted to all four fungicides tested. No fitness penalty was found for isolates resistant to multiple fungicides based on a statistical analysis of mycelial growth and conidial production.