All Issues

New fungus disease of prunes and apricots in California attributed to bruise injuries to bark from some shakers or other machinery Bark bruises on prune and apricot frees—resulting from mechanical harvesting injuries, particularly with certain types of limb or trunk shakers—are allowing the infection and spread of the serious canker disease caused by the fungus, Ceratocystis fimbriata. This injured branch of French prune had begun to heal until infected by the fungus which has now spread into healthy tissues above and below wound (arrows). Such branches are usually girdled and killed in two to three years.

Shaker injuries to the bark of trees can be minimized by careful operation of properly designed equipment. One careful grower, Andrew Micke of Tehama County, has been harvesting prunes with a commercial shaker for five years with no indication of serious damage. He has lost a few limbs but no trees. He was probably the first person to mechanically shake prunes with a tractor shaker, according to extension service records.

The rate of release of highly soluble inorganic fertilizers can be controlled by enclosing the fertilizer granule in a coating membrane. Factors which affect that rate under growing conditions were studied to gain a better understanding of the mechanism involved. The rate of release remains nearly constant until about two thirds of the fertilizer has been released; thereafter the rate drops off. After the first few days or weeks the rate may increase slightly.

During 1961 losses from stripe rust (Pucciniu glumarum) in California were higher than known for any previous year. The unprecedented severity of this rust in the Sutter Basin in 1961 may be attributed in part to favorable environmental conditions or, on the other hand, may indicate a recent shift in pathogenic races of the organism.

Feeding trials with rations including ground black-eyed cowpeas for swine resulted in reduced consumption and utilization of feed as well as lower gains—but there was no evidence of toxicity. Twenty-four growing hogs with an initial weight of about 80 pounds were fed a control ration and rations containing 20 per cent and 50 per cent ground black-eyed cowpeas (Vigna sinensis) for an experimental period of 70 days. As the percentage of black-eyed peas increased, gain in weight decreased. The pigs on the ration containing 50 per cent black-eyed peas gained about 38 per cent less weight than the controls.

Color and appearance of canned freestone peaches are affected by fertility levels and crop production levels according to taste panelists at Davis. Crop and fertility levels were also found to influence the size, soluble solids, acidity and firmness of the freestone peaches.

Good control of the green peach aphid, Myzus persicae (Sulzer), has been obtained during the past few seasons on north coastal counties lettuce and crucifer crops when proper spray or dust coverage was obtained with the recommended insecticides. These trials were conducted in areas of northern California where resistance to the recommended insecticides was claimed. Almost all failures to achieve adequate control could be traced to improper coverage, insufficient gallonage, or incorrect insecticide dosage. Nozzle arrangement and variations in pressure were studied in relation to gallonage output, but these were not found to be so important as speed of travel for achieving proper coverage and eventual control of the aphids attacking lettuce. Some of these trials were compared to commercial applications made by custom operators.

For the first time it has become possible to measure the ethylene concentration of the internal atmosphere of fruits. Melons, with their large cavities, are easiest to study, but by using small hypodermic syringes a sample of gas can be sucked out of almost any fruit. An ultrasensitive gas chromatograph then can be used to measure the amount of ethylene, even as low a concentration as one part per billion.

Wild species and primitive cultivated forms of the tomato will probably continue to serve as valuable sources of germ plasm for the breeding of improved varieties. Resistance to a series of devastating diseases, for example, has been bred into new tomato varieties. One of the aims of the present program is to determine the limits of tomato species hybridization and to investigate the nature of inheritance in the hybrid combinations.

Drill row preparation for cotton by deep tillage, with either vertical mulching or subsoiling, allowed better root development, accelerated plant growth and significantly increased yields in experiments at the U. S. Cotton Field Station, Shafter.

Soil reaction and weather conditions can influence responses to phosphorus fertilization, according to field trials with potatoes in the Tulelake area of northern California. Further research is needed to clarify the phosphorus availability of soils and potato plant utilization. Studies are also in progress toward obtaining a better understanding of the use of soil analysis to predict phosphorus requirements of these organic soils.

Excellent light quality for plant growth was attained in the new Davis campus phytotron (described in the November 1961 issue of California Agriculture) through the use of prismatic glass blocks to direct sunlight downward onto the growing benches—plus supplemental light when needed from photocell-controlled electric lamps. This article details preliminary experiments with plant growth in the large, early model phytotron, including comparisons with plant growth in conventional greenhouses.

During the past growing season, the Department of Agronomy has had under test 16 varieties of alfalfa and 36 varieties of red clover from western Europe. The purpose of these trials is to determine their seed producing capabilities under California conditions. Agriculturalists from western Europe who have traveled in California have been favorably impressed with the yields and quality of seed produced under California conditions. This has often been in sharp contrast with results in many parts of Europe where frequent rains reduce yields and damage quality.

Changes in cell structure caused by boron deficiency can be observed in great detail by electron microscopy. In contrast to the light microscope, which magnifies up to about 1500x, the electron microscope commonly magnifies from 1000x to 50,000x, with even higher magnification possible.

The application of irrigation water to agricultural soils, whether by surface flooding or sprinkling, may adversely affect the structure of the surface soil. If this is the case, the distribution of water and nutrients in the soil and consequently the uptake of nutrients by plants and plant growth may be affected by the method of water application.