Evaluation of Polyhexamethylene Biguanide for Control of Postharvest Diseases of Florida Citrus

G. Eldon Brown, M. Chambers


Polyhexamethylene biguanide (PHMB) is a water-soluble disinfectant, preservative, and sanitizer. Aqueous applications to citrus fruit (1000-4000 ppm) provided significant control of stem-end rot (SER) caused by Diplodia natalensis, sour rot caused by Geotrichum citri-aurantii, and green mold caused by Penicillium digitatum. Control of SER was not as effective as control obtained with thiabendazole (TBZ), but control of sour rot was significantly better than control with sodium orthophenylphenate (SOPP). Efficacy against green mold was similar to the efficacy of TBZ and imazalil. Though efficacy against SER was nominal, applications before degreening followed after degreening with TBZ were as effective as applications of TBZ before and after degreening. PHMB at 250-500 ppm eradicated G. citri-aurantii from simulated bin drencher suspensions as effectively as chlorine at 50 ppm. PHMB may function as the sole ingredient in bin drenchers and eliminate the need for chlorine, as long as fruit receive an application of TBZ on the packing line to achieve optimum control of stem-end rot.  

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