Ammonia fumigation for reducing green mould wastage in oranges during ethylene degreening

Abstract

The addition of ammonia to experimental cabinets reduced the development of green mould (Penicillium digitatum) wastage in oranges during ethylene degreening. The treatment consisted of introducing ammonia at a concentration of 6000 p.p.m. (v/v) three times every 24 hours throughout the three or four day degreening period. Ammonia gave excellent control of green mould wastage in wound inoculated oranges in preliminary laboratory tests. In an extensive experiment with Valencia oranges, surface inoculated with spores of P. digitatum, ammonia reduced green mould wastage when fruit was degreened at chamber loads of 25 and 50 per cent. These loads would represent the limits likely to be encountered commercially. The ammonia treatment did not cause rind damage to treated fruit. The evaporation of concentrated ammonium hydroxide solution is a practical and convenient method of adding ammonia to the degreening chamber.