All Issues

Some of the most valuable fruit varieties that have been continuously propagated by budding or grafting for centuries are highly complicated in their genetic constitution. Even if the plant breeder grows thousands of seedlings from such extraordinary varieties, no two seedlings closely resemble each other, and the progeny is extremely disappointing. Equally difficult is production of a new variety equivalent to a widely accepted one, but incorporating only one or a few improvements.

Foliar sprays for zinc deficiency in tomatoes are usually effective. Occasionally, however, plants fail to respond.

Avocado trees are fertilized according to the pattern used for citrus, but the leaves of both species differ considerably in composition. For example, the dry matter of healthy avocado leaves usually contains about 0.7% magnesium—about double that found in citrus leaves.

The major portion of California's field corn acreage is planted to hybrid varieties developed in the Midwest. These varieties have produced relatively high yields under ample water and essential plant nutrients. However, it seems unlikely that such varieties would represent the ultimate in adaptation to conditions in this state.

Annual clovers are seeded following brush removal in many range improvement programs in California. In the growing season following brush removal, brush seeds germinate, and old brush roots and crowns sprout. These seedlings and sprouts can be destroyed readily by 2,4-dichlorophenoxyacetic acid—2,4-D—sprays if they are applied soon after emergence. Such applications are most effective in the spring when growth is rapid. Unfortunately, at that time the seeded clovers are also susceptible to injury by 2,4-D.

Thirteen mineral elements are essential to animals, and must be present in their diet: calcium, chlorine, cobalt, copper, iodine, iron, magnesium, manganese, phosphorus, potassium, sodium, sulfur, and zinc. Under certain conditions or in certain limited areas, livestock production has been greatly improved by addition of one or more of these essential elements to the animals' diet. This finding has led to the extensive use of mineral supplements in livestock feeding even in areas where specific deficiencies have never been shown to exist. It is important that livestockmen know definitely the conditions and areas under which one or more minerals is likely to be lacking so that expenditures for unnecessary feed supplements for specific situations can be avoided.

Citrus leaves and fruit have recovered from freeze injury, after a short period of low temperatures as in the mid-November freeze in 1958. However, lower temperatures or longer low temperature periods might be beyond the recovery range.

There is a rest period for buds of deciduous fruit trees during which they do not expand into shoots or flowers even though environmental conditions for growth are favorable. Buds enter this period of rest shortly after they are formed in the late spring or early summer and develop only microscopically until after they are exposed to the chilling temperatures of winter. Cold temperatures bring about physiological changes in the bud which end the rest period and enable the buds to expand when conditions for growth become favorable in the spring.