Fungi associated with banana crown rot on field-packed fruit from the Windward Islands and assessment of their sensitivity to the fungicides thiabendazole, prochloraz and imazalil

Abstract

Crown rot of bananas causes serious losses in fruit exported to the UK from the Windward Islands (WI). A survey was undertaken to investigate whether the recent move to field packing, and the change from fungicide dipping to applying a fungicide-coated ‘crown pad’ directly to the crown, have affected the complex of fungal species that cause the disease. Isolations were made from rotted banana crowns from the WI over two years. In general, those fungi isolated were those previously reported to cause crown rot. The most common were Colletotrichum spp., Fusarium spp. and Botryodiplodia theobromae. The sensitivity of fungal isolates to the currently used fungicide, thiabendazole (TBZ) and also to imazalil and prochloraz was tested in vitro. Most of the fungi isolated showed expected levels of sensitivity to TBZ, but some isolates of Colletotrichum appear to have developed tolerance to this fungicide. In addition, fungi known to be relatively insensitive to TBZ, e.g. Nigrospora spp. and Penicillium spp., were isolated from diseased crowns at higher frequencies than expected. All the fungi tested, including those insensitive to TBZ, were sensitive to prochloraz and imazalil; these fungicides might therefore be considered as alternatives to TBZ for incorporation into crown pads.