Evaluation of brief potassium sorbate dips to control postharvest penicillium decay on major citrus species and cultivars

Several commercially important citrus species and cultivars were artificially inoculated with Penicillium digitatum or Penicillium italicum, immersed 24 h later for 5, 15, 30, or 60 s in water (control) or aqueous solutions of 3% (w/v) potassium sorbate (PS) at 20, 53, 58, 62, 65, or 68 °C, rinsed with tap water, and incubated at 20 °C for 7 d. The most effective treatments were PS applications at 62 °C for 30 or 60 s, which reduced both penicillium molds by up to 20, 25, 50, 80, or 95% on 'Clemenules' and 'Nadorcott' mandarins, 'Fino' lemons, 'Ortanique' mandarins, and 'Valencia' oranges, respectively. After 60-d storage at 5 °C, green mold and blue mold on 'Valencia' oranges treated with PS at 62 °C for 60 s were reduced by 96 and 83%, respectively. Treatments applied to nonwounded fruit before inoculation did not induce disease resistance. In semicommercial trials with 'Valencia' oranges, treatments with heated PS alone, PS combined with the fungicide imazalil (IZ), and IZ alone were all equally effective. On 'Marisol' clementine mandarins, the combination PS + IZ at room temperature allowed a significant reduction of the IZ doses needed for effective control of green mold.