|SEIYA, SAITO - Cornell University - New York|
|WILCOX, WAYNE - Cornell University - New York|
Submitted to: APS Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 3/15/2011
Publication Date: 5/1/2011
Citation: Seiya, S., Cadle Davidson, L.E., Wilcox, W. 2011. Practical resistance to fenhexamid Botrytis cinerea isolates from grapevines in New York. APS Annual Meeting. Phytopathology 101:S.
Technical Abstract: Fenhexamid is a fungicide used to control Botrytis cinerea on grapes worldwide. Resistance appears to be of a quantitative rather than qualitative nature, with minimum EC50 values that define a resistant phenotype proposed as exceeding 0.1 mg/L by some workers and 0.4 mg/L by others. However, little is known about the degree to which isolates of these sensitivities are controlled by the material when subjected to typical application rates in the field environments. In this study, a total of 388 B. cinerea isolates were collected from New York State vineyards and their sensitivity to fenhexamid was examined. Morphological, physiological and genetic characteristics of 12 strains with EC50 value greater than 0.1 mg/L were defined. Four isolates whose EC50 value of fenhexamid is 0.033, 0.105, 0.318 and 1.626 were used for in vitro inoculation tests to gauge whether they show practical resistance. Inoculation tests using grape berries showed that pre-inoculation spray with the field rate of 1.2 mg/L controlled B. cinerea more than post-inoculation spray with the same rate, regardless of EC50 value of four isolates tested.