Calag Archive

CANNING IS THE PRINCIPAL outlet for California apricots which account for nearly all of the USA pack. Softening of fruit in the can has been recognized as a problem for over 10 years. Annual evaluations by the Canners League of California of the foreign pack available on the European market indicate that softening is a problem for all major apricot producing countries.

FUNGAL CONTAMINATION with Bysso-chlamys fulva has been reported to be responsible for softening of canned apricots in South Africa. In Australia, apricot softening was attributed to the slow action of a heat-resistant pectic enzyme produced by the mold Rhizopus stolonifer. The softening was thought to be due to mold contamination in the orchard or following mechanical damage during post-harvest handling.

EVIDENCE FROM THESE tests showed that a single fruit decayed by Rhizopus arrhizus, and placed into a no. 10 can of healthy fruit before canning resulted in total disintegration of healthy fruit during six months' storage at room temperature. Addition of a single Rhizopus stolonifer decayed fruit also resulted in significant softening within a six-month period in fruit from one out of three orchards. There was little change in rating of fruit after nine months' storage, but in one treatment 48% of the good Tilton fruit showed initiation of softening, with flesh starting to disintegrate, and soft to the touch.

CANNED APRICOTS in Australia are believed to be softened by heat-tolerant pectolytic enzymes from the black bread mold, Rhizopus stolonifer (Ehrenb. ex Fr.) Lind. Australian workers have duplicated softening problems by adding a Rhizopus-rotted fruit or juice from a rot lesion to cans. Fungi were killed by heat-processing at 100°C (212°F) for 10 minutes but a portion of their pectolytic enzyme activity remained. The Australian work has now been duplicated independently in two California studies.

AMONG CURRENT ISSUES in water management, perhaps none is more critical than evaluating the use of waste water in irrigation. Waste water includes return flow irrigation water, treated municipal effluent, and low quality waste water from other miscellaneous sources. Opinions range from those which view such use as completely impracticable to those which view reclaimed water as superior to present water supplies. At issue is the possible cost penalty from increased salts and nutrients in reclaimed water used to replace present water.

THE OPTIMUM PLANTING time for wheat and barley in Imperial Valley is between December 15th and January 15th, which makes them excellent crops to follow cotton and late-plantings of grain sorghum. The growing period (and production) of the cereal crops might be increased if the time between the harvest of cotton or grain sorghum and the planting of wheat and barley could be shortened, by eliminating some irrigation and tillage operations. These possibilities were investigated during an experiment designed to compare wheat (Siete Serros and Anza) and barley (CM 67) in the winters of 1971-72 and 1972-73 under maximum and minimum soil preparation following cotton and grain sorghum.

COOL NIGHT TEMPERATURES 10 to 16 days before heading cause many rice florets to be sterile. The direct cause of sterility is failure of pollen grains to germinate because they are immature, and contain little if any starch. In two successive years, 12.5 and 12.8% of the florets in rice fields grown for certification were found to be sterile, as determined by random samples of panicles taken from fields. The range in sterility in 59 fields checked in 1972 was from 2.7% to 34.8%. Rice growers have recognized the problem for many years and have correctly associated it with late planting, cold water at the inlet boxes, and heavy nitrogen fertilizer applications.

These studies show that early walnut harvest minimizes insect-damaged kernels and maximizes quality and resulting kernel value. Direct relationships exist between harvest date and nut quality. Differential in value within walnut growing districts is directly dependent on time elapsed between date of maturity and harvest. Temperatures during harvest may account for differences in value between districts. Once nuts are removed from the tree, picking should proceed as rapidly as possible to maintain optimum kernel color and value. Rate of loss in kernel quality is directly proportional to increasing air temperature. Kernel temperature of about 140°F appears to be the threshold for onset of kernel darkening, and is reached in the sun at air temperature above 90°F and in the shade at air temperatures of 104°F or greater. Once threshold kernel temperatures are attained, substantial loss in value can occur within nine hours. Threshold kernel temperatures are reached fastest when nuts are harvested during midday. Rapid pickup is essential at that time to maintain quality. Shaken nuts with hulls still intact, typical in harvest of early varieties, reach threshold kernel temperatures faster and remain at those temperatures longer than nuts without hulls. Sun-exposed nuts on the tree remain cooler than those exposed to similar condition on the ground. This suggests that growers should store nuts on the tree for short periods of time if delays in picking are anticipated.

IN 1928, THE EUROPEAN DUSKY-VEINED walnut aphid, Panaphis juglandis (Goeze), made its first appearance in the Western hemisphere in Oregon's Willamette Valley. The aphid first appeared on walnut trees in California near San Jose in 1952. By the following year it had spread over much of the walnut-producing area of the San Francisco Bay region. Recently the aphid has been found in Contra Costa, San Mateo, Butte, El Dorado, San Joaquin, Glenn, Sutter, Colusa, Tehama, Stanislaus, and Nevada counties.