title: Sensitivity of Venturia inaequalis to trifloxystrobin.
abstract: The sensitivity of Venturia inaequalis to trifloxystrobin was monitored by both in vitro (spore germination) and in vivo tests (on apple seedlings). There was good correlation between the in vitro and in vivo results. Baseline sensitivity was established with 95 bulk isolates from Europe between 1995 and 1998 which showed a narrow sensitivity range-factor of up to 17 between the least and most sensitive isolates. Monitoring of populations originating from trifloxystrobin-treated and untreated orchards between 1995 and 1999 showed only sensitive isolates and no performance deficiencies were reported. Data also show that trifloxystrobin is not cross-resistant to anilinopyrimidines and triazoles, but is cross-resistant to kresoxim-methyl, another strobilurin which also inhibits the cytochrome bc1 enzyme complex at the Qo-site in the respiration chain of fungal mitochondria (QoI inhibitors). Under experimental conditions from a specific trial site in Switzerland, where trifloxystrobin has been tested since 1994, isolates containing conidia resistant to Qo inhibitors were detected in 1997 and 1999. However no obvious performance deficiencies were reported. Nevertheless these results demonstrate a risk for the development of practical resistance in V inaequalis to Qo inhibitors and therefore a need to apply resistance management principles strictly.
authors.affiliation: Syngenta Crop Protection Münchwilen AG, Research Biology, 4332 Stein, Switzerland. ruth_b.kueng_faerber@syngenta.com
authors.forename: Ruth B Küng
authors.initials: RB
authors.lastname: Färber
authors.forename: Khoon Min
authors.initials: KM
authors.lastname: Chin
authors.forename: Neil
authors.initials: N
authors.lastname: Leadbitter
mesh_terms: D000085:Acetates / Q000633:toxicity*; D001203:Ascomycota / Q000187:drug effects* / Q000254:growth & development; D019069:Cell Respiration / Q000187:drug effects; D025141:Drug Resistance, Fungal; D014450:Electron Transport Complex III / Q000187:drug effects; D005060:Europe; D005659:Fungicides, Industrial / Q000008:administration & dosage / Q000633:toxicity*; D007097:Imines / Q000633:toxicity*; D027845:Malus / Q000382:microbiology; D008689:Methacrylates; D008826:Microbial Sensitivity Tests; D008928:Mitochondria / Q000187:drug effects; D010935:Plant Diseases / Q000382:microbiology; D013170:Spores / Q000187:drug effects / Q000254:growth & development; D000073739:Strobilurins; D014230:Triazoles / Q000633:toxicity
chemical_list: D000085:Acetates; D005659:Fungicides, Industrial; D007097:Imines; D008689:Methacrylates; D000073739:Strobilurins; D014230:Triazoles; D014450:Electron Transport Complex III; C467051:trifloxystrobin