Late fall time to complete post-harvest orchard projects We don't have slow months in almonds. November and December are as busy as any other month. At this time, almond growers should be occupied in planing or doing the following: zinc sprays, pruning, pre-emerge herbicide applications, dormant spray and winter sanitation.
Fall application of zinc is effective in maintaining adequate levels of zinc in the tree. This means that there is no need to include zinc fertilizer with any of the cover spray during the growing season. In addition, fall application of zinc will cause tree defoliation, permitting the tree to go into dormancy. In the Southern San Joaquin Valley in mild winter, almond trees can maintain their leaves well into January. Leaves on the tree can interfere with the dormant spray coverage. Another benefit of defoliation is the elimination of shot hole disease inoculum for the following spring.
Pruning is a cultural practice that should be done after harvest. In the Southern San Joaquin Valley, we don't have any problems pruning young trees in the winter. However, this can be a problem in the Northern San Joaquin Valley.
Young trees are pruned to create a strong structure. All limbs with narrow angles containing embedded bark should be eliminated during the first three years of training. Light should cascade down to the tree head. This is accomplished by eliminating some of the limbs growing through the center of the tree. One should thin out some limbs to allow light into the canopy, but not be aggressive enough to open windows around the canopy.
Pruning doesn't increase yields. This was demonstrated by John Edstrom, Colusa County farm advisor. If pruning doesn't increase yields, why prune then? Mature trees are pruned for light and height management.
Lower fruiting wood An almond orchard is considered mature when it gets to be seven or eight years old. At this age, if light doesn't penetrate the inside of the lower canopy, the lower fruiting wood starts dying. This can be prevented by having upright scaffolds. Heading cuts and tying during training encourages upright scaffolds. If upper limbs come down and lay over each other, then, one must thin out some of the branches. This will eliminate some crop, but it will promote upright growth. This pays off when the orchard matures.
In Kern County , the highest reject levels occur in old orchards that are impossible to clean due to their height. Mature trees should be maintain to a height of 20 feet. At this height, during sanitation, the worker will reach mummy-containing branches. The lowering of an orchard height should be done gradually using a pruning tower.
Foliar applied herbicides have been effective in controlling weeds on the berm area. Unfortunately, for this method to be effective, it requires multiple applications. This has made this weed control method very expensive. Furthermore, this method has created control problems with the following weeds: silverleaf nightshade, morning glory and postrate knotweed. To overcome these problems, pre-emerge herbicides can be used in some orchards. There are new regulations by the Department of Pesticide Regulation that regulate the use of pre-emerge herbicides. Before you use them, you need to check with your local Agricultural Commissioner.
The dormant spray should be done in the first week of January. At this time, the trees are fully dormant, beehives will not be in for more than four weeks, and insect pests are just beginning to be active. The dormant spray is effective in controlling San Jose Scale, peach twig borer, brown and European red mites.
Sanitation is the removal of leftover nuts from trees. It is the key to the control of navel orangeworm. Research projects have shown that sanitation and early harvest can eliminate the need for in-season sprays.
Sanitation should be done in December-January or as soon as the rain or fog season begins. Mummy nuts can be removed from the tree by mechanical shaking or by hand poling. The trees should be cleaned to less than one mummy per tree.
Sanitation should not be delayed until just before bloom. By this time, sanitation can lose its effectiveness in reducing navel orangeworm infestation. Furthermore, the shaker at this time, can cause major damage to the root system, since by bloom time, we have major root activity in almond trees.