Calag Archive

The host and geographic range of the pitch canker pathogen has greatly increased since it was first discovered in California in 1986. Most significantly, it now affects many pine species, including native stands of Monterey pine, and has made a transgeneric jump to Douglas fir. Isolated occurrences of the disease have been found as far north as Mendocino County. Insects are strongly implicated as vectors of the pathogen, and long-term management appears to be dependent on the development of resistant tree varieties. In infested regions, the planting of Monterey pine and other pine tree species should be undertaken with caution.

Effects of alternate-year pruning over four seasons on fruit production, quality and net revenues per tree compare favorably to those for traditional annual pruning methods. Alternate-year pruning may be feasible for growers interested in reducing pruning costs in a particular season. However, the cost to prune trees in the alternate year significantly affects revenues per tree.

The incidence of pitting and impact bruising on ‘Brooks’ sweet cherries was greatest when the flesh temperature was near 1 °C (34°F), intermediate near 10°C (50°F), and lowest near 20°C (68°F). Therefore ‘Brooks’ cherries should be handled at temperatures between 10° and 20°C (50° and 68°F) during packing to minimize surface damage. However, because of increased respiration rates at higher temperatures, cherries should be cooled to 0°C (32°F) within 4 to 6 hours of harvest.

This section showcases cooperative research efforts between UC personnel and growers in several regions of the state. Findings from suck demonstration projects and field research can provide the groundwork for further studies in other fruit-producing areas of California. We publish these articles in response to the groundswell of grower interest in more sustainable farming practices. — Ed.

Codling moth and rosy apple aphid limited production and profitability in the organic Granny Smith apple production system in the northern San Joaquin Valley. Over the course of this 4-year study, organic techniques were developed to control codling moth, but not rosy apple aphid, which is an occasional pest. Fertility was easily maintained in the organic system with leguminous cover crops, which also served as a habitat for insects beneficial to apple production.

Apple growers are interested in organic production to take advantage of higher market prices while reducing pesticide inputs. In a Sonoma County study, it was relatively easy and comparable in cost to maintain good tree vigor organically. However, severe insect and disease problems greatly reduced the yield and market value of organic apples compared to conventionally grown apples. The organic production system was also more expensive and more complicated to manage, creating greater risk for the grower. Although organically grown fruit could be sold at higher prices, the price differential was not sufficient to justify the losses, the need for increased management and the additional risk involved.

Conventional and organic semidwarf Granny Smith apple production systems were compared during 3 years of conversion to certified organic management on California's Central Coast. Yields were significantly higher in the organic production system in 1989 and 1991 due to significantly greater fruit load. Growth indicators such as tree girth, terminal growth, leaf area, and so on, did not generally differ, but tissue levels of nitrogen were generally higher in leaf and new wood bark tissue in the conventional system, while phosphorus levels were generally higher in tissue of the wganically managed trees. Key sconomic pest damage did not differ significantly in any year, although fruit and leaf damage due to some lepidopterous secondary uests was greater in some years in the conventional system. Apple kaf hoppers showed significant hcreases in leaf damage in the organic system. Price premiums for wganic apples consistently proiuced higher per-acre return for this system.

Pheromone confusion worked best in isolated orchards with low codling moth populations. In areas where codling moth developed three to four generations and apples were exposed to egg laying for each generation, mating disruption with pheromones was not consistently successful in suppressing codling moth populations. For an orchard with an established history of codling moth infestation, well-timed insecticide sprays had to be integrated with the confusion technique to obtain adequate control.