Mario Viveros
UCCE Farm Advisor, Kern County
Deciduous Tree Fruits and Nuts
May 10, 2002
The 2002 almond crop in the southern San Joaquin Valley looks very good. Based on the first estimate, this year's crop is predicted to be around 940 million pounds. If this is true, this year's crop will be the largest in the history of almond production.
Limb breakage is a good indicator of crop size. Some growers have been taking limbs out of the orchards since mid-April. This is just the beginning. We will continue to see this type of activity until the end of June. The reason is due to a continuous dry weight accumulation into the nut. This weight accumulation ceases at hull split which ends in July. In theory then, we can have limb breakage in June and through July.
What can one do about the breakage? There is very little one can do about it. The only thing to do is to tip limbs that have a heavy set. This will prevent the limb from breaking and allow it to grow upright. Young trees, up to seven years of age, should be tied. Furthermore, trees should be double tied when they are three, four and five years old to reduce or prevent limb breakage.
A very heavy crop means more demand for nitrogen, water and more mite pressure. To determine a good nitrogen rate, the grower needs to estimate his crop. A good rule of thumb is to apply 1/10 of a unit of nitrogen for every meat pound produced by the orchard. Example: If the estimate is 3,000 meat pounds per acre, the grower needs to apply 300 units of nitrogen. One hundred sixty units of nitrogen can be applied in March for crop and shoot development. Then, 80 units of nitrogen for continuous crop and shoot development. The balance of 60 units of nitrogen should be applied post-harvest for next year's crop.
It has been my experience that heavy crops require more irrigations than light crops. Unfortunately, I don't have data to support this observation. However, you should follow the tree's evapotranspiration (ET) and soil moisture status during the growing season.
It is not a good idea to deficit irrigate almonds. Every physiological process, root and shoot growth, bloom, fruit set, nut development, flower bud differentiation requires the presence of water. In the southern end of the San Joaquin Valley, we have shown that one can deficit irrigate almonds for two weeks at the onset of hullsplit for "Hull Rot" control. However, we can't deficit irrigate almonds in the post-harvest period because this will decrease next year's yields.
Water deprivation for almonds is not recommended during nut growth and development for the following reasons: 1) yield reduction due to small and shriveled kernels, 2) in-shell product from Nonpareil, Carmel and Sonoras may not be possible because of foreign material and 3) varieties like Nonpareil, Carmel, Price, Fritz and Mission may be too sensitive to water deprivation.
The key for a successful mite management control is adequate irrigations. Mites become a problem when the temperature goes up and/or trees are stressed for water. When trees are under water stress, leaf temperature increases which can create conditions for mite flare-ups.
Mite management requires intensive monitoring of the orchard. It should be checked every two weeks from March to May 1st. Then, it should be checked every week from May 1st to the end of August. When using the presence-absence sampling technique, a spray may be necessary when the level of infestation reaches 40%. One allows this level of infestation to get this high when predatory mites are present. When there are no predatory mites present, the spray should be applied at a lower level of infestation.