CULTURAL TIP: USING TREE OBSERVATIONS TO ASSESS CULTURAL MANAGEMENT DECISIONS
In a recent Greensheet it was suggested that avocado growers make observations about their trees by taking notes in a small pocket sized notebook. It is important to note general, as well as specific details about the state of your trees. These notes will prove helpful when reviewing management decisions throughout the year. One approach to note taking is to concentrate on what visual markers the trees display that then can be tracked over time. In spring some of the important questions to ask are: How well have the trees come through winter? What is the flowering like on the trees? Has there been any freeze damage? Are the fruit at the best commercial size?
How have the trees come through winter? - For avocado trees to produce fruit they need a good supply of the right building blocks. These building blocks are delivered by a healthy root system to high quality leaves. Problems with roots or leaves will show up in the overall health of the canopy. Consequently, assessing the health of the canopy is an important skill for a grower to develop. Over winter, the roots and leaves degrade through the effects of overwatering, soil disease pressure, cold temperatures and photo-oxidation (too much light for the temperature). If these issues have plagued your trees through winter, very often the canopy of the tree will show less than ideal leaf health. Monitoring the general health of the canopy by keeping notes is a good way to follow the trees overall health at flowering and fruit set. The health of the canopy at these stages should provide an indication of the cropping potential of the trees, in which success would be trees that appear capable of a good fruit set.
What is the flowering like? - In order to have good crops of fruit the tree has to produce flowers with good potential to set fruit. The easiest time to assess the strength of the flowering is in spring. Also important is the timing of flowering, the number of weeks over which the trees flower and the weather during flowering. Bee activity is an indication of the potential strength of the fruit set.
Bee activity - Too few bees working on the flowers can indicate a poor fruit set even if flower numbers are high. An estimate of bee numbers may allow poor pollinator activity to be avoided as there may be an opportunity to increase
the number of bees in the grove during flowering. A simple way to estimate how many bees are active on the trees is to count the bees while walking slowly around a tree in a minute. Generally the more bees the greater the amount of pollination. Fewer than 10 bees per tree is less than ideal, and could suggest poor fruit set if further cultural management practices to aid in pollination are not taken.
Has there been any freeze damage? - In some winters it is possible that periods of cold temperatures can damage the flowering potential of the trees. Often freeze damage is severe enough to be easily seen as damage to leaves, shoots, fruit and any developing flowers. Hidden freeze damage to the tree may show up long after the freeze as a poor fruit set. Healthy avocado trees can often tolerate a freeze better than less healthy trees. Following up on the effect of a freeze or freezes during winter in spring can be useful in evaluating the success of frost management on the grove.
Are the fruit at the best commercial size? - Commercial success in growing avocado fruit is not just the number of fruit a tree produces, but also the size of the fruit. Achieving commercially valuable sizes is a goal for all California Avocado growers which will influence harvest decisions. Fruit that are small in spring can often be left on the tree to increase in size to meet market requirements. However, good crops of mature fruit left on the tree to size can reduce fruit set for the next year at the tree competes for resources. Harvesting some of the mature fruit before or during flowering and fruit set can be useful in reducing the competitive effects of the mature crop. By keeping track of fruit size, harvest times can be selected that could be helpful in reducing the competition between the mature crop and the newly setting crop.
This article, in further detail, can also be found here:
CaliforniaAvocadoGrowers.com/assets/Uploads/Growers-Site/Cultural-Management/Cultural-Tips/April-15-Tip.pdf
