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-l 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-' a.i. DPA. None of the treatments injured the fruit. Control of scald by 2000 mg litre-' a.i. DPA or ethoxyquin was not impaired by adding thiophanate-methyl (I g litre-l a.i.) or calcium chloride (10 g litre-l) 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 I ) of 3 mg kg-1 and 10 mg kg-*, respectively, even where 4000 mg litre-l 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.

SUMMARYIn two apple orchard trials, single high volume sprays of 25–50 mg permethrin/ litre greatly reduced numbers of the phytosend predatory mite Typhlodromus pyri whether the spray was timed pre‐bloom at growth stages from ‘bud‐burst’ to ‘late green cluster’ or post‐bloom in June. At ‘bud‐burst’T. pyri were partially protected in hibernating sites on the bark, but the lethal effect of the spray was only delayed; no appreciable selectivity could be obtained by this early timing. Bioassays showed that the persistent toxicity of permethrin residues on bark or on leaves declined to a low level within 20 days, and was related to the decline in residue levels determined by G.C. analyses. Residues were detectable for 3 months or longer. Resurgence of spider mites, Panonychus ulmi, occurred within 2 months after all spray timings, and effective predation by T. pyri was only fully re‐establised after several months. In one trial, apple rust mite, Aculus schlechtendali also increased when T. pyri was reduced by spraying. Tydeid mites were killed by permethrin.

Trials in 1975 and 1976 showed that deposit levels of the fungicide binapacryl, on the leaves of bush trees of Cox's Orange Pippin (Cox) after mist blower spraying, varied inversely with tree spread. Deposit levels were measured on young mildew‐susceptible leaves from a well‐sprayed zone around the periphery of the tree canopy at a height of 1.5 m. Low deposit levels in large, dense trees were associated with poor mildew control. Leaves from the smallest trees had deposit levels considerably greater than those found for larger trees (in another nearby orchard) which had adequate mildew control. Fungicide deposit levels on leaves from up to five different zones of trees of three different sizes (the largest trees were of the variety Bramley's Seedling) were measured in 1977. The smallest trees had significantly higher deposit levels than the larger trees in the lower centre and lower outside zones of the trees, whereas both orchards of Cox had the same (commercially acceptable) level of mildew infection at the end of the season. Leaves from zones less accessible to spray had lowerdeposit levels than those nearer the sprayer.

The biological effectiveness of deposits of binapacryl applied by a single high pressure nozzle was compared with similar deposits applied by twin low‐pressure nozzles. Equal foliar deposit densities were obtained from the two systems but the single nozzles gave marginally better control of apple powdery mildew and fruittree red spider mite.

The mildew fungicide triforine is incompatible with calcium chloride used to reduce the incidence of bitter pit in apples. Two commercial non-ionic surfactants delayed sedimentation in spray mixtures containing both triforine and calcium chloride. The biological efficiency of triforine, alone or with calcium chloride plus surfactant, was tested in an orchard trial which included binapacryl, alone or with calcium chloride, as 'standard' treatment. Triforine (weekly or fortnightly) controlled mildew on Cox's Orange Pippin and Golden Delicious better than binapacryl, and the addition of calcium chloride did not affect adversely the control by either fungicide. The added calcium chloride had little effect on the deposition and persistence of the fungicides. The inclusion of calcium chloride in spray programmes slightly improved the yields (both cultivars) and russet grade (Cox only) associated with each fungicide. Calcium chloride sprays, whether mixed or alternated, increased the calcium levels in postharvest fruit for both varieties, and decreased the incidence of bitter pit for Cox after storage for 53 months. No adverse effect was associated with the inclusion of the surfactants in tank mixtures containing either fungicide.