Relative sensitivity to the fungicides benomyl and iprodione of Botrytis elliptica f rom Taiwan and the Northwestern U.S.A.

Abstract

Isolates of B o t rytis elliptica were tested for growth on potato dextrose agar as well as potato dextrose agar amended with discriminatory concentrations of benomyl (1μg a.i. ml- 1) or iprodione (10μg a.i. ml- 1) . Fourteen of these isolates originated from Washington or Oregon State in the USA, and the remaining 48 isolates were from Taiwan. Relative fungicide sensitivity was assessed by dividing the extent of growth after 96 h on amended media over the growth on unamended medium. There was no significant difference in growth rates on unamended PDA between isolates from Taiwan compared to those from the U.S.A.; however isolates from Taiwan showed higher relative growth, 4-fold or 2-fold greater, respectively, on benomyl or iprodione-amended media than isolates from the U.S.A. More research is needed to determine whether these Taiwan isolates showing less sensitivity to benomyl or iprodione also exhibit resistance in the field to normal fungicide application rates.