| Abstract: | Recent changes in the antioxidant regulations in the UK and the need to evaluate the effectiveness of scald control chemicals in the presence of other post-harvest chemicals led to a comparative study of the effects of diphenylamine (DPA) and ethoxyquin on scald development in Bramley's Seedling apples. A range of concentrations (1000–4000 mg litre?1 a.i.) of DPA completely controlled scald on Bramley apples kept in controlled atmosphere storage for 241 days; ethoxyquin at equivalent rates was less effective. Only partial control of scald was achieved with 500 mg litre?1 a.i. DPA. None of the treatments injured the fruit. Control of scald by 2000 mg litre?1 a.i. DPA or ethoxyquin was not impaired by adding thiophanate-methyl (l g litre?1 a.i.) or calcium chloride (10 g litre?1) although the measure of control was reduced when both fungicide and calcium chloride were added. Calcium chloride caused lenticel injury which was aggravated by adding ethoxyquin but reduced by incorporating DPA. The concentrations of ethoxyquin and DPA residues on the fruit immediately after treatment were within the limits required by UK legislation (see reference 1) of 3 mg kg?1 and 10 mg kg?1, respectively, even where 4000 mg litre?1 had been applied. An initial residue concentration of 2.3 mg kg?1 DPA was associated with complete control of scald. Residue levels, particularly of DPA, declined rapidly during the first month of storage. |
