Studies were made on the effects of inherited factors, (scions and rootstocks) and field factors, (districts and climates) on the 'typiness' of Red Delicious apples produced in fruit growing districts of the eastern and western coasts of Australia. 'Typey' fruit is that which has pronounced calyx lobes and which attracts premium prices at market. Richared, Royal Red and Starkrimson cultivars were far more 'typey' than the common Red Delicious, whereas Hi-Early and Royden Red were inferior in this respect. Rootstocks had little effect on 'typiness'. The districts of Orange and Batlow in New South Wales produced the most 'typey' fruit. The extent to which 'typiness' was developed in the fruit was related to mean air temperature in the period of seven days following full bloom.

The new growth regulator 2-chloroethanephosphonic acid (Ethrel)3 was applied to apple and peach branches or young trees at several stages of development from prebloom to harvest. Application at 1000 to 2000 ppm during the prebloom to early postbloom stages on several apple cultivars virtually eliminated all fruit with little or no phytotoxicity. Peach foliage and shoots were more sensitive to the chemical. Vegetative growth was checked and flower bud formation promoted in some cases. From one week after bloom to 4 weeks after bloom, fruit set could be reduced but it was not possible to eliminate the fruit in all cases without phytotoxicity. Application from then until a few weeks before maturity had little effect on abscission. Fruit abscission at maturity was promoted with application of Ethrel.

Results of experiments over two seasons at two locations in New South Wales and one in Western Australia have shown that 'typiness' of Red Delicious apples can be improved by the use of blossom applications of the plant growth regulators gibberellin (GA4/7) and N6benzyladenine (BA). Benzyladenine was the more effective of the two materials tested, and stimulated both an increase in the length : diameter ratio (L/D) of the fruit and development of the calyx lobes. The gibberellins were less consistent in their effect. Sprays combining both GA,/, and BA in equal proportions provided little additional benefit to that obtained with BA alone at the equivalent strength.

Trials were conducted in three successive years to test the response of Granny Smith, Jonathan, and Delicious apple varieties to Alar (succinic acid 2, 2-dimethyl hydrazide) applied at various times and concentrations. The results confirmed overseas reports of reduced shoot growth, increased fruit set, reduced fruit size, reduced pre-harvest drop, and, in some cases, increased blossoming the following spring. The Jonathan variety was less responsive to the growth retardant than Delicious, which was, in turn, less responsive than Granny Smith.

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