New advances in the development of quality assurance norms for the South African avocado export industry

As part of the continuous improvement of South African export avocado quality, the storage potential of avocados from 60 orchards in the most problematic Kiepersol area was determined during the 2003/04 season. The mineral content of the fruit was measured on a monthly basis as from December 2003 to March 2004. Storage trials commenced upon reaching the 82% fruit moisture content level during April and continued on a weekly basis until moisture content levels of approximately the 62% were reached. SmartFresh TM applications were made at the commercial dosage throughout the trial as well as at a higher dosage when fruit moisture content levels dropped below 71%. In Fuerte and Pinkerton the incidence of grey pulp was found to increase in a familiar fashion as the season progressed. The incidence of the disorder was, however, higher in Fuerte than in Pinkerton. In the absence of SmartFresh™, grey pulp was already present at around 75% fruit moisture in fruit from nitrogen rich orchards, while in nitrogen poorer orchards it started to appear at around the 68% mark. When SmartFresh™ was applied at the commercially used concentration, the incidence of grey pulp only occurred where fruit moisture content was 66% or less. With the higher SmartFresh™ dosage it was possible to stretch the grey pulp-free period to when the fruit reached 64% moisture. In Hass, very little to no grey pulp occurred in orchards where the pulp nitrogen was within specifi cation. In a single Hass orchard where the nitrogen was considerably higher than the recommendation at the January cut-off point, the incidence of grey pulp was high at the beginning of the season while it disappeared towards the end of the season. This pattern is completely opposite to the norm. However, we have observed similar trends in the past and it would seem to have been brought about by heavy rains approximately 2 months prior to harvest. In so far as black cold damage was concerned, Fuerte and Pinkerton displayed classical incidence patterns. In both cultivars, black cold damage was a problem at the beginning of the harvest window and not the end. However, several Hass orchards showed an uncharacteristic pattern in that black cold damage developed towards the end of the harvest window. The lesions did, nevertheless, seem to differ morphologically from the early season lesions. Early season lesions were typically larger and coalesced while late season lesions were smaller and did not readily coalesce. We are presently of the opinion that the late season black cold damage was also brought about by the climatic conditions responsible for the uncharacteristic early season grey pulp observed in the one Hass orchard. In general, the quality of Edranol fruit was poor, while that of Ryan was excellent. This year’s results further appeared to confi rm last year’s notion that an association exists between the large-lesion, classical, early season, black cold damage symptoms and the iron content of the fruit. However, in the case of the smaller end-of-season lesions, iron would seem to play less of a role while calcium defi ciency on the other hand may possibly be a contributing factor.