Walnuts Archives - West Coast Nut





Walnuts



Distribution Uniformity:

By Dani Lightle, UC Cooperative Extension Orchard Systems Advisor, Glenn, Butte & Tehama Counties

What is Distribution Uniformity? Distribution Uniformity (DU) is a measure of how uniformly water is being applied across the orchard, or whether certain parts of the orchard are receiving more water than others. It is a measure of the irrigation system. DU is a different measure than irrigation efficiency, which is a measurement of how well the applied water matches the crop water requirements. Irrigation efficiency is a measurement of how well you—the irrigator—applies a correct amount of water at an appropriate frequency. However, it is impossible to have a high irrigation efficiency without also having high distribution uniformity (Figure 1). (more…)

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Anaerobic Soil Disinfestation in Walnuts

By Cecilia Parsons Associate Editor

Pulling and replanting a walnut orchard presents many challenges. Planning for treatment of orchard soils to ensure a healthy new orchard includes identifying problems ahead of time and choosing appropriate prevention. Chemical fumigation has been standard practice for replanting orchards, but alternatives are being studied. Though not currently used in commercial walnut production, there have been some large trials to determine if anaerobic soil disinfestation (ASD) is useful in suppressing soilborne pathogens and pests when replanting walnut orchards. Trials were conducted at the UC Kearney Agriculture and Research Center. The practice is being studied as an alternative to using chemical fumigants due to increased restrictions on their use. Methyl bromide has been the fumigant of choice for many years, killing both soil pathogens and pests along with weed seeds. Anaerobic soil disinfestation is a biologically based integrated management strategy for soilborne diseases that aims for sustainable production without the use...

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Update on Sterile Insect Program for Control of Navel Orangeworm

By Houston Wilson, Asst. Coop. Extension Specialist, Kearney Ag. Center, Dept. Entomology, UC Riverside
and Chuck Burks, Research Entomologist, USDA-ARS, San Joaquin Valley Agricultural Sciences Center

Sterile insect technique (SIT) makes use of large numbers of sterile insects which are released into wild populations as part of an area-wide integrated pest management (IPM) control strategy. Insects are typically mass-reared in a controlled environment and then ionizing radiation (e.g. x-rays, gamma rays) is used to induce genetic mutations that lead to sterility. The basic idea is that introduction of sterilized individuals into the wild population will limit the successful reproduction of wild individuals and lead to an overall reduction or even eradication of the target pest population (Knipling 1955). Mating with sterile individuals can reduce populations by either directly blocking reproduction or through inherited sterility in which offspring are actually produced but are themselves sterile (North 1975). Releases can include both males and females, although some programs utilize just one sex, and this is typically due to specific biological or ecological requirements.   The concept of using...

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Mating Disruption: A Crucial Tool for Nut Growers

By Kathy Coatney Editor

Mating disruption for navel orangeworm (NOW) has been widely tested throughout California with numerous research studies, and peer-reviewed research has demonstrated its efficacy. Mating disruption is a very simple process. Females emit pheromones, males use those pheromones to find the female. If an orchard is flooded with artificially produced pheromone the entire orchard smells like a female and the males struggle to find the real females. If they don’t find each other, they don’t mate, and if they don’t mate there are no eggs, no larvae, and less overall nut damage.   Mating Disruption in Almonds and Pistachios Navel orangeworm is a major and costly pest of almonds and pistachios for growers and processors. Currently, growers use winter sanitation and chemical sprays for control, but mating disruption is another important tool at their disposal. How mating disruption works is dispensers contain an artificial pheromone. They are placed in the orchard...

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Managing and Controlling Canker Diseases in Almonds and Walnuts

By Cecilia Parsons Associate Editor

Options to control Botryospaeria (BOT) diseases in tree nut crops include good sanitation and cultural practices to reduce the amount of inoculum in the orchard. University of California plant pathologist Themis Michallides covered the range of BOT diseases that affect walnut, pistachio and almond trees and how growers can reduce infection at the South Valley Nut Conference in Tulare.   Panicle and Shoot Blight of Pistachio Panicle and Shoot Blight of pistachio was discovered in 1984 in a commercial orchard in northern California and has become a disease of major importance. Buds infected by B. dothidea either will not emerge or will emerge, but the flower or shoot eventually dies. Symptoms of the infection are dark lesions at the base of shoots, rachises and mid ribs of leaves. Later in the growing season, brown, blighted shoots and leaves are easily seen among healthy foliage. Buds are highly susceptible to infection...

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