Identification of antagonists for controlling foliar fungal pathogens of citrus

Bang-Jau You, Huiqin Chen, Kuang-Ren Chung


Four saprophytic fungi producing unknown toxic compounds were identified from citrus groves and were evaluated for control of two citrus foliar fungal diseases, Alternaria brown spot and melanose. The toxic compounds secreted in cultures were antagonistic to pathogens as they reduced the growth of citrus fungal pathogens considerably and induced stubby, swollen and fragmented hyphae. The inhibition was unaffected or slightly increased by heating to 95C for 15 minutes. Production of the toxic compounds by antagonists was markedly influenced by the composition of the media. Preliminary tests revealed that the saprophytic fungi reduced disease incidence of Alternaria brown spot on tangerine and melanose on grapefruit. The toxic compounds produced by the saprophytic fungi may be useful in developing effective bio-fungicides and providing an alternative for disease management for citrus growers in Florida.


Alternaria alternata; Diaporthe citri; antagonism; biocontrols; phyllospheres

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Proc. Fla. State Hort. Soc.     ISSN 0886-7283