Calag Archive

Studies have been conducted for the past two seasons on the action of predators against the pear psylla. Most of the work has been done at the University of California Deciduous Fruit Station, San Jose, on a block of pears that has been left untreated. The trees at this orchard had received all cultural requirements except the application of pesticides. The orchard suffered heavily from pear psylla attack from 1959 through 1961. In 1962 predators (anthocorid bugs and lacewings) brought the pear psylla population to a low level. The trees (Winter Nellis on Old Home-Farmingdale root-stock) responded by growing vigorously, whereas in previous seasons, growth had nearly ceased and the foliage was yellow and sparse. Studies were continued in 196S to determine if the predators would continue to regulate the pear psylla population.

Differences in yield, sulphate-sulfur (SO₄-S) concentration, and total sulfur (S) up-take were found among five competing annual grassland species growing at different levels of available S at Hopland. Yield response of subclover, soft chess and ripgut to S fertilization increased as the season advanced, but the concentration of total S and SO₄-S in the plants decreased. Sulfur deficiency was indicated by the SO₄-S concentration in each of the species where no S had been applied. The SO₄-S concentration in subclover at flowering gave the best single indication of S status when all levels of available S were considered. Where no S was applied, there was little or no uptake of S after the first harvest date, but where S was applied, it continued to be absorbed by subclover, soft chess and ripgut up to the third harvest. The increase over the check was much greater for subclover than for any of the other species.

Mechanical harvesting of Bartlett pears was attempted in 1960 using a block of sixty-year-old trees, designed specifically for hand harvesting, at the George and Walter Brown pear ranch, Santa Clara County. The lower limbs were so near to the ground that a catching frame could not be driven beneath the trees and the fruit had to be dropped onto straw in the initial trials. After a month in cold storage the fruits were peeled and then graded for mechanical damage, including bruising (brown spotting). An average of 48% of the fruit was damaged and unacceptable for processing. Brown spot bruising accounted for 32% of the damage. This damage was presumed to be from fruits hitting twigs, branches and other fruit while falling.

Benefits of “precision tillage” or deep tillage directly under the drill row for cotton were generally substantiated in the fourth year of San Joaquin Valley trials. Substantial increases in cotton growth, yield and earliness were obtained on coarse-textured soils at the U. S. Cotton Research Station, Shafter, and in Madera County tests. However, precision tillage trials on fine-textured soils in Tulare County did not show these benefits.

All of Ventura county's 2,900 acres of avocados is in the southern half of the county, with the majority in the Santa Clara Valley-Oxnard Plain and the Las Posas Valley-Camarillo areas. Most of the avocados are growing in 17 different soil series, but over 25 soil series are involved. Fortunately, avocado root rot has been found in only 21 locations and has damaged a total of only 21 acres. Since many avocados are growing on restricted or poorly drained soils, it is fortunate that the root rot fungus, Phytophthora cinnamomi, has not been spread very widely in the county.

The development of better soil and water management procedure requires understanding of plant response to various soil water relationships. It is especially important to know how the water status of plants, as affected by soil suction, influences the rate of important metabolic and synthetic reactions. This paper reports the results of a preliminary study on the effects of soil water content on the rate of photosynthesis, the exceedingly important reaction through which plants manufacture carbohydrates from atmospheric carbon dioxide (CO₂).

The leucoanthocyanins occupy an important position among the water-soluble organic compounds present in the tissues of plants. They have been implicated as being responsible for the astringent taste of unripe fruits. They are responsible for the chill haze that develops in beer and for the browning of white wines. The desirable fullness of taste and body of such juices as apple, berry and grape and of fruit wines is also attributed to the astringent effect of the leucoanthocyanins. They influence the storage stability of wines and juices.

Results of this study indicate that certain herbicides may be used to reduce soilmoisture depletion by weedy plant species and thus insure good stands of grasses, even when seeded in seasons of low rainfall. Vigorous grass plants are more likely to result if soil-moisture reserves are high at the time of seeding.