Many homeowners with ornamental olive trees prefer to avoid having sidewalks and other concrete patios stained by the ripe fruit that fall off of the tree later in the season. Napthaleneacetic acid ammonia salt can be applied that will cause flower drop. This material is sold under several trade names including Fruit Fix Concentrate 800, K-Salt Fruit Fix 200 and K-Salt Fruit Fix 800 by AMVAC Corp.; Liqui-Stik Conc. by Platte Chemical Co.; and Olive Stop by United Horticulture. This type of material is available at nurseries or the home-garden section of department stores.
If you do not want any fruit on the tree, you should make three or four applications because bloom will occur over several weeks. Applications made at early-, mid- and late-bloom periods will have a good chance of causing all of the blossoms to drop. Make sure that you thoroughly cover the foliage of the tree. Only the blossoms covered with the material will drop.
If you want to cure your own olives, you will want to spray late in the bloom period to reduce the fruit load. An application made late in the bloom period will thin the crop. This will result in a crop of fewer larger fruit.
Peaches, nectarines and apples
Thinning fruit of these trees can greatly increase size and quality of the crop. If all of the young fruit are allowed to mature, you will have many small fruit at the end of the season. In addition, if the fruit are not thinned, it may reduce the number of flower buds produced for next season's crop.
Early thinning will have the greatest affect on fruit size and on next year's bloom. However, it is best not to thin flowers or young fruit because bad weather or other conditions that stress the plant can cause some drop especially at early stages of crop development. Therefore, by waiting until the fruit are about the size of a dime, you are increasing the chances that you will not lose additional fruit after thinning.
There are several things to consider when deciding which fruit to pick off. There are a few rules regarding how much fruit should remain, which is based on the number of leaves. In general, it is recommended that one fruit be left for every 40 to 75 leaves on the tree. Early varieties need more leaves per fruit and dwarf trees need fewer leaves per fruit. Always leave the larger fruit. It is easy to begin by picking off the smallest or damaged fruit. It is best to evenly space the fruit along the branch, but the small fruit will never reach the size that the larger fruit will even if they are spaced well.
Note about Aleppo pines
Within the last several weeks, needles have died and some branches have died back on many Aleppo pines in Imperial Valley. This condition has occurred before in the Imperial Valley and other areas in the Desert Southwest. The most recent widespread occurrence of this problem in Imperial County was during winter 1999-2000.
Typically, the needles at the tops of some trees suddenly turned a bronze color. The symptoms usually occur on the southeast side of the tree. No bacterial or fungus disease is associated with this problem.
Older reports on this condition attributed these symptoms to low soil moisture and drying winds. To reduce severity of Aleppo pine blight maintain uniform water supply throughout the year and irrigate so that water is available to a depth of at lest 5 feet. Avoid over-fertilization, which would encourage the rapid production of tender growth that is susceptible to adverse weather conditions.
Although there is no definitive proof, there may be an association with winter sunlight and air pollution.