Use of Phosphite Salts in Laboratory and Semicommercial Tests to Control Citrus Postharvest Decay

Cerioni, L., Rapisarda, V. A., Doctor, J., Filckert, S., Ruiz, T., Fassel, R., and Smilanick, J. L. 2013. Use of phosphite salts in laboratory and semicommercial tests to control citrus postharvest decay. Plant Dis. 97:201-212. Potassium phosphite (ICP) concentrations that inhibited the germination of 50% of Penicillium digitatum conidia were 229, 334, 360, 469, 498, or 580 mg/liter at pH 3, 4, 5, 6, 7, or 8, respectively. Increasing phosphate content in media reduced phosphite toxicity. To control green or blue mold, fruit were inoculated with P digitatum or P. italicum, then immersed 24 h later in KP, calcium phosphite (CaP), sodium carbonate, sodium bicarbonate, or potassium sorbate for 1 min at 20 Oiler for each at 25 or 50 degrees C. Mold incidence was lowest after potassium sorbate, CaP, or ICP treatments at 50 degrees C. CaP was often more effective than ICP but left a white residue on fruit. KP was significantly more effective when fruit were stored at 10 or 15 C after, treatment compared with 20 degrees C. Acceptable levels of control were achieved only when KP was used in heated solutions or with fungicides. ICP was compatible with imazalil (IMZ) and other fungicides and improved their effectiveness. ICP increased thiabendazole or IMZ residues slightly. Phosphite residues did not change during storage for 3 weeks, except they declined when ICP was applied with IMZ. KP caused no visible injuries or alteration in the rate of color change of citrus fruit in air or ethylene at 5 mu l/liter.