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Open Access Publications from the University of California

Volume 74, Issue 2, 2020

Issue cover
Cover Caption: A prescribed fire on private land in El Dorado County, February 2020. The objective of this burn was to reduce fire hazard in the wildland–urban interface on the Georgetown Divide. The area had been high-grade logged 15 years earlier and was pre-commercially thinned two years earlier. Photo by Rob York.

Research and Review Articles

Boons or boondoggles: An assessment of the Salton Sea water importation options

Several ways to address the looming ecological disaster that is the Salton Sea have been proposed — including water importation. Here we considered two options: importing ocean water from the Sea of Cortés and leasing water from agricultural users in the Imperial Valley. We estimated the monetary costs for importing Sea of Cortés water to the Salton Sea and compared that with the costs of transferring water from agricultural users to the Salton Sea. We found that leasing water from agriculture would be substantially cheaper than ocean water imports. Additionally, all the infrastructure for leasing water from growers exists, which means water transfers could begin immediately. That is important given the present and increasing environmental and human health damages that are occurring at the Salton Sea.

Traditional market-animal projects positively influence 4-H enrollment

The 4-H Youth Development Program (4-H) teaches life skills. An understanding of the factors that drive participation in the California 4-H program can help the organization target its efforts to increase enrollment and benefit more California youth as they move toward adulthood. 4-H has long been associated with market-animal projects, but the effect of these projects on enrollment is not known. In this study, 7 years' worth of enrollment data from 27 Northern California counties was evaluated with linear modeling techniques to determine the impact of market-animal projects (beef, sheep and swine) on program participation. The analysis demonstrated that market-animal projects produce significant, positive effects on enrollment. Each beef project contributed nearly four new members to county enrollment; a single sheep project yielded just over two new members; and two new swine projects produced a single new enrollment. Region and population density influenced membership but year within the study period did not. These results demonstrate the multiplicative effect of beef and sheep projects on county 4-H enrollment.

UC pistachio cultivars show improved nut quality and are ready for harvest earlier than ‘Kerman’

California pistachio growers have traditionally grown only one female cultivar (‘Kerman’) and one male pollenizer (‘Peters’). Starting in 2005, the UC breeding program released several improved cultivars, which are being planted on increasing acreage — and tested now under commercial conditions at multiple sites over multiple years. We conducted six experimental trials in the San Joaquin Valley to evaluate the performance of the UC cultivars ‘Gumdrop’, ‘Golden Hills’ and ‘Lost Hills’ and their associated UC male pollenizers ‘Famoso’, ‘Randy’ and ‘Tejon’ against the performance of the traditional pair, ‘Kerman’ and ‘Peters’. The new cultivars demonstrated a range of earlier bloom and harvest dates than ‘Kerman’ and some improved nut quality characteristics, such as a higher percentage of split, in-shell nuts. Results indicate that by growing the new female cultivars and synchronous pollenizers, producers can avoid the peak harvest period for ‘Kerman’, when equipment and processing facilities are limited, and maintain or improve their yield and nut quality.

Grape erineum mite: Postharvest sulfur use reduces subsequent leaf blistering

The occurrence of eriophyid mites (Calepitrimerus vitis [rust mites] and Colomerus vitis [erineum mites and bud mites]) in vineyards worldwide is associated with leaf deformation, stunted shoot growth and reduced yield potential. In the North Coast region of California, leaf blistering by the erineum strain of Colomerus vitis is the most widespread symptom of eriophyid mite damage. Unlike rust and bud mites, erineum mites are generally considered a nuisance pest that is incidentally controlled by sulfur-dominated management programs for powdery mildew. However, recent reductions in the use of sulfur have allowed erineum mite populations to expand, highlighting the need for alternative management options. In this study, we posited that, during autumn, mites moving to buds from erinea (leaf blisters) to overwinter could be susceptible to sulfur applications. During four growing seasons, we documented patterns of mite movement to identify key sulfur application timing. We found the greatest numbers of migrating erineum mites from late September to early November. Concurrently, in replicated trials, we evaluated the efficacy of postharvest sulfur applications to reduce blistering. Sulfur applied during the migration period in 2013 appeared to eradicate leaf blistering in the 2014 growing season. In subsequent trials, sulfur treatments reduced blistering to less than 10% incidence, compared to 40% to 50% incidence in control plots.

Supporting evidence varies for rangeland management practices that seek to improve soil properties and forage production in California

California is increasingly investing in policies and programs that promote soil stewardship on natural and working lands as a way to help achieve multiple goals, including improved forage production and climate change mitigation. To inform the growing expectations for rangeland management activities to promote such services, we conducted an evidence synthesis assessing how four commonly suggested practices (silvopasture, prescribed grazing, compost application and riparian restoration) affect a suite of soil properties and plant-related metrics throughout the state. We extracted data on soil properties that are potentially responsive to management and relevant to soil health. We also extracted data on aboveground forage production, forage nitrogen content and herbaceous species richness. Our search resulted in 399 individual soil observations and 64 individual plant observations. We found that the presence of oaks had the largest effects on soil properties, with soil organic carbon, microbial biomass and other measures of soil fertility increasing beneath oak canopies. The presence of grazing increased compaction and total nitrogen, and decreased pH. Compost applications did not significantly affect any of the measured soil properties, but did boost forage production. Due to a lack of published data, we were unable to characterize the influence of rangeland riparian restoration on any of the soil or plant metrics in our review.

News and Opinion

Burn permits need to facilitate – not prevent – “good fire” in California

The weather last fall was unusually favorable for private landowners to carry out prescribed burns to reduce wildfire hazard. Burn permits, however, made burning unnecessarily difficult. Safe and effective prescribed burns can benefit from changes in permitting.

COVID-19 and California farm labor

COVID-19 may accelerate trends in California agriculture toward mechanization and the use of guest-worker programs.

How is coronavirus affecting agriculture in California?

An interview with UC Cooperative Extension experts about the effect of the coronavirus pandemic on food production.

Recent blue oak mortality on Sierra Nevada foothill rangelands may be linked to drought, climate change

UC Cooperative Extension and landowners join forces to probe possible causes of mysterious blue oak mortality in the Sierra foothills.