Calag Archive

Any agriculturist viewing California croplands from an airplane at low altitude must be impressed by the broad view he gets. Entire fields, from 10- to 640-acre blocks, may be seen in one glance. Relative thriftiness of plants in various parts of the field are easily observed. Patterns of crop variation caused by nonuniform fertilization, irrigation, drainage, salts, soil texture, soil depth, disease, and inscct damage are often more evident from the air than they are at close range on the ground. The economic severity of the conditions, however, must still be determined on the ground by measuring such factors as plant growth, crop yield, product quality, and, ultimately, net return.

During the late 1950's, the Egyptian alfalfa weevil invaded alfalfa in the desert regions of the southwestern United States. In 1974, it caused in excess of 18 million dollars in damage (1974 California Department of Food and Agriculture Report). This is not surprising as, under certain circumstances, this pest can completely defoliate a crop. In addition, the routine pesticide applications which have been directed against this pest appear to have induced secondary pest outbreaks of other formerly innocuous pests (e.g., aphids, mites and various Lepidoptera), which also, require further pesticide applications to control them. The problems of increasing pesticide applications and the associated costs are so severe that they jeopardize the economical cultivation of alfalfa in the central valley of California.

Club root, incited by Plasmodiophora brassicae (Woronin), is one of the most serious diseases of plants of the crucifer family and is a threat to crop production wherever it occurs. In heavily infested soil, it is capable of destroying a crop before it reaches market maturity.

Durado, an early maturing Japanese plum, resulted from a cross made in 1966 (see figure). It was selected in 1969, propagated at the Kearney Horticultural Field Station in the same year, and placed in several authorized grower-cooperative trial plantings in Fresno, Tulare, Kings, and Kern counties in 1972 and 1973. Several of these test plantings bore fruit in 1975. It was tested as Selection 9,27-58.

Specimens of this new aphid were unknowingly collected by one of the authors from alfalfa near Bakersfield, California in 1974. The samples were taken to detect lygus bug parasites and the aphids in the samples were not counted. Fortunately, the samples were preserved for other observations. When the new aphid reached outbreak numbers in 1975, the Bakersfield samples were reexamined and specimens of the new aphid were identified by R. C. Dickson, U.C. Riverside.

Pear scab (Venturia pirina) has come more prevalent in recent years in the north coastal regions, especially in Mendocino County. A closely related fungus causes apple scab (Venturiu inaequalis) but does not affect pears, although the life cycles, infection requirements, and even control measures for apple and pear scab are remarkably similar. While apple scab research is ample and worldwide in scope, the applicability of some of this research to pear scab California has not been established.

Many of the citrus and avocado orchards near the foothills of Ventura and Orange counties are damaged by root disease and excessive wetness from hillside seepage. The damage is most severe during wet years or when the adjacent hills are excessively irrigated (see fig. 1). Dense subsoil and steep topographical conditions cause excess water from rain or irrigation to seep underground downslope creating a drainage problem (see fig. 2).

Five underground drip irrigation systems with varied, emitter spacings were evaluated for alfalfa seed production in the Imperial Valley. Previously, higher seed yields had been produced with a 50-centibar soil water tension at 9 inches below surface drip lines than with soil water tensions of 10, 100, and 200 centibars (see California Apiculture, November 1975). Since surface drip lines are subject to sunlight and mechanical damage, we began an evaluation of five underground drip irrigation systems for alfalfa seed production in November 1973 at the Imperial Valley Conservation Research Center near Brawley. The five systems with indicated emitter spacings were: (1) Chapin, continuous (a biwall system with orifices spaced 32 inches on the inside tube and water seeping through a nylon-sewn seam on the outside tube); (2) Chapin, 8.”; (3) Watersaver, 24”; (4) Nelco, 24”; and (5) Anjac, 36”. The main objective was to determine the effect of emitter spacings on alfalfa seed yield rather than to compare commercially available drip lines.