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March in the Avocado Orchard - 1997
Spring is a time when the grower thinks of replanting and topworking unproductive trees or reworking trees to pollinator varieties. It is also the time when warm weather is starting the weed season. Plants are starting to grow with warmer weather.
In replanting, it is always best to look at the whole orchard. If you are considering replanting a single tree in an older orchard, determine whether replacement is worth all the hassle of tanking the water necessary to meet the needs of that single tree versus the irrigation pattern that is being provided to the older trees. In many instances, the opening that the missing tree offers will be filled in by surrounding trees in the not to distant future. Single tree replacement in older orchards is always fraught with competition with neighboring trees for water, light and nutrients, and in many instances it is best to just let the neighboring trees grow to fill the gap.
If there are many trees that need to be replaced in an orchard with several good looking remaining trees, it is always easier and in the long run more productive to remove the remaining trees and start anew. By starting all trees on the same irrigation pattern with the same access to light and nutrients, it is possible to have more even growth and ensure that the trees get their needs met.
March is also the time when topworking can begin to be considered. Spring is when the trees are most receptive to grafting, and it is still cool enough that grafts have the best chance of taking. There has been much speculation on the value of having pollinator varieties in the orchard for Hass. This past year I have seen numerous instances of the increased pollination and set of Hass that have had pollinators nearby.
In the past as much as 20% of the orchard was recommended as being planted to "B" pollinators, such as Bacon or Walter Hole. Even though these trees produced fruit of a lesser value than Hass, the improved set on the Hass in some years has been viewed as more than compensating for the lesser value from the pollinator trees. With the introduction of Lamb 122 which is a "B" variety and fruit similar to Hass, the decision to topwork should not be such a difficult decision. Topworking to other varieties, such as Pinkerton and Edranol, on a small scale is good pollination insurance. It will insure that pollen is available when Hass is receptive, and in spite of the generally lower value of the fruit, there will continue to be a greenskin market and at times greenskins have commanded a higher price than Hass.
Weed control should be on the minds of growers this time of year. Do the job before it gets too late. If necessary mow weeds before spraying if they are too large. As long as weeds are kept in check, you might even consider them as a cover crop, mowing them back before they become competitive with the trees and before they have set seed and become resistant to decay. Soil organic matter in orchards without a leaf cover is always low and soil fertility can always be improved with more organic matter.
For young trees consider putting down a layer of coarse mulch around the base of the tree to prevent weed competition. If it is put down on top of the drip emitter, it will significantly reduce weed growth around the wetted pattern. Make sure that the mulch does not accumulate around the trunk, because the moist mulch can cause various fungal diseases.
Moist soil from winter rains also makes ideal conditions for gophers. Especially in young orchards, this is the time to insure that a trapping/baiting program is in place so that their populations do not get out of hand. This is also the time to begin looking for Persea mite, and if present, a predator mite release program should begin.