Efficacy of preplant treatments of gladiolus corms with combinations of acibenzolar-S-methyl and biological or chemical fungicides for suppression of fusarium corm rot [Fusarium oxysporum f. sp. gladioli

Abstract

In 2003-2005, corms of gladiolus (Gladiolus ×hortulanus) susceptible to Fusarium oxysporum f. sp. gladioli were soaked for 30 min in Actigard® 50WP (50% in wettable powder; acibenzolar-S-methyl (ASM)), with or without biological or chemical fungicides, to determine if any treatment or combination of treatments provided season-long suppression of fusarium corm rot in the fields in Hamden, Connecticut, United States. Corms treated with ASM produced 48% more marketable flower spikes than untreated corms, and the value of the area under the disease progress curve (AUDPC) was reduced by 12%. However, this reduction was not significant. The chemical fungicides Medallion® 50WP (fludioxonil) and Terraguard™ 50WP (triflumizole) reduced the AUDPC by 27% and 23%, respectively, and almost doubled the number of marketable flower spikes. None of the biological fungicides (Actinovate™ SP (water-soluble powder), Companion®, MycoStop®, and PlantShield™), nor the chemical fungicide 3336™ 50WP, were effective in reducing the AUDPC or increasing the number of spikes. No interactions were noted between ASM and the fungicides, except when ASM was combined with Heritage™ 50WP (azoxystrobin). ASM and Heritage 50WP used separately were not effective in reducing the AUDPC but, when combined, they provided season-long suppression of corm rot. Continued research on ASM may lead to an effective new strategy for reducing corm rot on gladiolus and related ornamentals.