EFFECT OF A NOVEL POTASSIUM BICARBONATE-BASED FORMULATION AGAINST PENICILLIUM DECAY OF ORANGES

The efficacy of the novel potassium bicarbonate formulation Karma (Certis Europe) for controlling Penicillium decay of orange fruit was tested. In vitro trials were carried out by amending potato dextrose agar (PDA) medium with different Karma concentrations, thereby revealing a complete inhibition of Penicillium digitatum, P. italicum, and P. ulaiense growth at 0.3, 0.3, and 0.2% (w/v), respectively. In vivo trials using dipping and spraying application strategies were conducted on Valencia late and Tarocco, two sweet orange cultivars with different degrees of susceptibility to Penicillium rot. Fruit treated with unformulated potassium bicarbonate (PB) or water served as controls. When applied by dipping, Karma and PB at 3% significantly reduced the incidence of Penicillium decay of cv. Valencia late oranges, i.e. by 79 and 31%, respectively. On the other hand, when applied by spraying, 6% Karma and PB were needed to completely inhibit decay incidence. On cv. Tarocco oranges, Karma and PB applied at 3% by dipping reduced the percentage of Penicillium decay, by a significant 87 and 68%, respectively. However, when applied by spraying at 6%, no difference was observed between the two treatments. Overall, Karma performed better than PB in controlling Penicillium rots and dipping proved to be the best application strategy.