ETHYLENE GAS BURN OF WASHINGTON NAVEL ORANGES - A FORM OF ANTHRACNOSE INDUCED BY DEGREENING AND CONTROLLED BY BRUSHING OR APPLYING FUNGICIDES

The effect of several postharvest treatments on rind damage to Washington navel oranges during ethylene degreening was assessed. Application of hot benomyl dips (500 mg/L) or washing the fruit on revolving brushes prevented rind damage for all fruit colours and ethylene concentrations (0-2000-mu-L/L) tested. Application of either of the fungicides benomyl (unheated) or prochloraz also reduced rind damage. Imazalil had less effect, while guazatine only slightly reduced rind damage. Rind damage was attributed to the development of anthracnose when dormancy of latent infections of Colletotrichum gloeosporioides was broken. It is recommended that when susceptible oranges are degreened, they are treated with benomyl, preferably at 50-degrees-C, or washed over revolving brushes. Ethylene concentrations should also be kept as low as practicable to reduce the risk of rind damage.