Use of phosphite salts in laboratory and semi-commercial tests to control citrus postharvest decay

CERIONI LUCIANA; RAPISARDA, VIVIANA A; DOCTOR J.; FIKKERT S.; T. RUIZ; R. FASSEL; SMILANICK JOSEPH L.

PLANT DISEASE

AMER PHYTOPATHOLOGICAL SOC

Año: 2013 vol. 97 p. 201 - 212

0191-2917

Potassium phosphite (KP) 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 hr later in KP, calcium phosphite (CaP), sodium carbonate, sodium bicarbonate, or potassium sorbate for 1 min in 20 g/liter of each at 25 or 50oC. Mold incidence was lowest after potassium sorbate, CaP, or KP treatments at 50oC. CaP was often more effective than KP, but left a white residue on fruit. KP was significantly more effective when fruit were stored at 10 or 15oC after treatment compared to 20oC. Acceptable levels of control were achieved only when KP was used in heated solutions or with fungicides. KP was compatible with imazalil (IMZ) and other fungicides and improved their effectiveness. KP increased TBZ or IMZ residues slightly. Phosphite residues did not change during storage for 3 weeks, except they declined when KP was applied with IMZ. KP caused no visible injuries or alteration in the rate of color change of citrus fruit in air or 5 µl/liter ethylene.