NOVEMBER AND YIELD

The avocado tree often has an alternate bearing yield pattern. This pattern is often ascribed to pollination and fruit set being reduced by low temperatures during flowering and in the initial stages of fruit set in spring mid-October to mid-November. For avocado cultivars the best temperatures for the most effective pollination is thought to be 25°C during the day and 20°C nights. New Zealand avocado orchards are in regions with mean annual temperatures about 14°C considered to be at the climatic margin for successful avocado production. Therefore, the temperature during flowering and the initial fruit set period should allow avocado growers to predict fruit set. A study was conducted over several years to determine the relationship between temperature and yield. The yield of orchards was not correlated with average temperature, the number of pollination events, average temperature during flower opening, chilling hours or heat unit hours. It was not possible to make predictions of yields based on measurements of temperatures over the main flowering and fruit set period. There appeared to be an upper limit of yield at each average temperature that indicates temperature limits yield if other undefined factors are not limiting or are negative and lower the yield. The relationship between yields and temperature is more complex than often thought. Other factors limiting yield may be the phenology of the alternate bearing cycle, plant hormone relationships, pollination efficiency and tree nutrient status. By considering temperature a