Control of green mold on florida citrus fruit using bicarbonate salts

Jiuxu Zhang, Patricia Swingle

Abstract


Carbonate and bicarbonate salts have been reported to be effective for green and blue mold control of citrus fruit. Evaluation of potassium bicarbonate (PBC) for the suppression of Penicillium digitatum mycelial growth and the control of green mold was conducted in vivo using both inoculated and naturally infected orange fruits and an aqueous packingline drip system. Test data showed that PBC actively suppressed the mycelial growth of P. digitatum in vitro with an ED[sub5][sub0] of 0.08%. Using both inoculated and naturally infected 'Navel' oranges, the concentration of PBC greatly affected the efficacy for green mold control and a rate of 3.4% was demonstrated to be the best concentration to reduce green mold incidence under the test conditions. Choosing 3.4% PBC in two additional tests using 'Valencia' or 'Pineapple' oranges, PBC significantly (P =0.05) reduced green mold incidence in two tests. However, in all tests PBC at 3.4% never significantly reduced stem-end rot caused mainly by Diplodia natalensis. PBC at 3.4% achieved a similar efficacy as imazalil at 0.1% for green mold control in all 4 tests, and it also performed similarly to thiabendazole (TBZ) at 0.1% for green mold control in three tests in which TBZ was used as a standard fungicide. When PBC was compared to sodium bicarbonate (SBC) for decay control, PBC and SBC at the same concentration of 3.4% performed similarly, both effectively controlled green mold, but not stemend rot. No fruit damage was observed in any test. The information of this study suggests that bicarbonate salts such as PBC and SBC could be alternative chemicals for citrus green mold control under the current packing system in Florida.

Keywords


diplodia natalensis; penicillium digitatum; p. italicum; blue mold; potassium bicarbonate; postharvest handling; postharvest decay; sodium bicarbonate; stem-end rot

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