Postharvest rots and internal disorders of 'Hass' avocado (Persea americana) fruit develop during the latter stages of fruit ripening, with symptoms first appearing when fruit are minimally ripe but often becoming quite severe before the fruit are oversoft. Fruit ripened at 20°C and assessed at the same stage of ripeness, just before the flesh becomes oversoft, had fewer postharvest rots if they had been previously stored at 4 or 6°C, than if they had been stored at either lower or higher temperatures. Postharvest disorders increased with increased length of storage. Fruit failed to ripen properly at 30°C. Even at 25°C (a temperature typically experienced by fruit exported from New Zealand), the level of postharvest disorders was greater than in fruit ripened at 20°C. Best final quality was obtained with fruit coolstored at 6°C and then ripened at 15 °C. However, if fruit are to be ripened at c. 25°C, then final quality was better if the fruit were not coolstored but held at a temperature closer to the final ripening temperature. Fruit from a single orchard block, harvested, coolstored, and ripened together, individually reached minimum eating ripeness over an 8-day period. Fruit which ripened earliest had the fewest disorders, with later ripening fruit typically having high levels of postharvest rots and internal browning.

Several sources of variation in the concentration of soluble solids in kiwifruit at harvest have been identified and quantified. Within a single fruit the major variation was in the distribution along the longitudinal axis of the fruit where differences of 1.2070 soluble solids were' found between the 2 ends of fruit with a maturity index of 8.8. The position of fruit on the vine also has an effect, with areas being identified that yield fruit which, on average, have higher soluble solids concentrations than fruit from other areas. Other sources of variation between different fruit have also been quantified, including an effect of crop density in the vicinity of the fruit sampl~d and a smaller effect of fruit size. Components of variance between vines or within a vine were compared. The variation between individual fruit sampled randomly from a vine increased with increasing maturity index of the crop. The sources of variation identified in this study will be used to suggest improvements to the sampling system to increase the precision of maturity testing of kiwifruit in New Zealand.

S U M M A R YXylem sap was extracted from cut branches of stone-fruit and pip-fruit trees at different times of the year, and analysed for nitrogen and carbohydrate content. Growth of Stereumpurpureum was measured in the different sap samples in vitro. Nitrogen and carbohydrate levels in xylem sap from peach trees were highest in late winter and early spring, and these samples supported most growth of S. purpureum. At full bloom the levels of nitrogen and carbohydrate in xylem sap from stone-fruits (peach, nectarine, plum, cherry) were several times greater than in sap from pip-fruits (apple, pear), and the growth of S. purpureum in sap from stone-fruits was approximately ten times that in sap from pip-fruits.The results suggest that seasonal variations in susceptibility of stone-fruits to silver-leaf disease, and the greater susceptibility of stone-fruits than of pip-fruits, are due to differential ability of their xylem saps to support growth of S. purpureum.

S U M M A R YAscospores of Didymella applanata were released in rain and dew throughout the summer, the highest concentrations occurring in May when new raspberry canes were emerging.Infections on new canes did not develop until later in the season, when ascospore concentrations were low although pycnospores were present. Lesions first appeared near the base of the green canes just below the point of attachment of the petioles; they were not associated with obvious leaf, petiole or bud infections. Once maturation of the canes occurred, further infection was prevented.