Effectiveness of pH and Butylated Hydroxyanisole (BHA) on Fungicidal Activity of Certain Fungicides for Controlling Green and Blue Mold Diseases on Orange Fruits

Abstract

Green and blue molds caused by Penicillium digitatum and P. italicum, respectively, are the major postharvest cause of orange fruit decay, resulting in economic losses in the citrus industry. Four fungicides (i.e. boscalid, kresoxim-methyl, boscalid+kresoxim-methyl and cyprodinil+ fludioxonil) and the antioxidant butylated hydroxyanisole (BHA) were evaluated separately and in mixtures against P. digitatum and P. italicum causing green and blue mold diseases of navel orange fruits, respectively. The in vitro studies showed that higher (8-11) and lower (3-5) pH values reduced the growth of P. digitatum and P. italicum. Also, the results showed that the premixed fungicide formulations were more efficient in inhibiting the mycelial growth of fungi than individual forms. Both fungi tolerated high concentrations of BHA. The potency of fungicides and BHA against fungi growth was interestingly increased at pH 3 and 9. Also, the fungitoxic activities of fungicides were increased by adding BHA to fungicide-amended medium. The in vivo studies illustrated that all the separated fungicide treatments, particularly the mixtures of them, effectively controlled the diseases, while the separate BHA treatments slightly reduced the incidence of diseases. Also, the addition of BHA to the fungicides greatly increased their efficiencies against the incidence of diseases. Moreover, the potency of fungicide and BHA was considerably increased at pH values of 3 and 9.