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Open Access Publications from the University of California

Volume 72, Issue 4, 2018

Issue cover
Cover Caption: Leaves on a coffeeberry shrub (Frangula californica) display symptoms of infection by pathogens in the genus Phytophthora at an ecological restoration site on Mori Point, Pacifica, in San Mateo County. Three articles in this issue (pages 205, 208 and 217) address a serious concern for the restoration of natural areas in California: The inadvertent infestation of restoration sites with multiple Phytophthora species via infected planting stock.
Phytophthora contamination of ecological restoration sites

Research and Review Articles

Soil- and waterborne Phytophthora species linked to recent outbreaks in Northern California restoration sites

Many studies around the globe have identified plant production facilities as major sources of plant pathogens that may be released in the wild, with significant consequences for the health and integrity of natural ecosystems. Recently, a large number of soilborne and waterborne species belonging to the plant pathogenic genus Phytophthora have been identified for the first time in California native plant production facilities, including those focused on the production of plant stock used in ecological restoration efforts. Additionally, the same Phytophthora species present in production facilities have often been identified in failing restoration projects, further endangering plant species already threatened or endangered. To our knowledge, the identification of Phytophthora species in restoration areas and in plant production facilities that produce plant stock for restoration projects is a novel discovery that finds many land managers unprepared, due to a lack of previous experience with these pathogens. This review summarizes some of the key knowledge about the genus Phytophthora in general and lists some of the many soilborne and waterborne species recently recovered from some California restoration sites and plant production facilities.

Three new Phytophthora detection methods, including training dogs to sniff out the pathogen, prove reliable

Multiple species of Phytophthora have been identified in production facilities of plants used in reforestation and restoration projects. There's a risk that infected plant stock will lead to Phytophthoraspecies establishing and spreading in habitats that, having never experienced their presence, may be highly susceptible to infection. Eradication of these pathogens, once introduced into wildlands, is impossible. Thus, monitoring nursery stock is key, but sampling large production lots is still prohibitively complex and expensive. We tested three new sampling approaches that are practical for large production lots: baiting of small portions of symptomatic plant material pooled from multiple samples in addition to whole plant sampling; baiting of bench irrigation leachate; and training dogs to identify the pathogens. The first two methods detected Phytophthora with a high confidence level directly from batches of plants, but they are not designed to identify each infected plant specifically. Trained dogs identified individual batches of soil and water containing Phytophthora with a 100% accuracy and the research is continuing, to see if dogs can recognize the pathogen from individual infected plants and plant parts and discriminate its smell from other scents.

Dependence on policy revenue poses risks for investments in dairy digesters

Manure-sourced methane emissions from livestock operations in California will soon be subject to new regulation, as required by Senate Bill 1383, which was signed into law in 2016. Regulations, beginning in 2024, will require reductions in methane emissions from livestock manure, with a 40% reduction target by 2030. The California dairy industry accounts for most of the manure-sourced methane emissions in the state and, in order to reduce these emissions, government experts and authorities have encouraged expansion of anaerobic digestion of dairy waste — especially to produce transportation fuel. Renewable natural gas for vehicle fuel, produced from manure at digesters, is eligible for substantial federal and California environmental credits, which are now projected to contribute the bulk of the revenue for qualifying digesters. This article shows that investments in digesters, because they depend heavily on revenue created by government policy, rather than on market-based sales of natural gas, are highly vulnerable to the risk of policy change or even minor technical adjustments in environmental regulations. Without secure projections of revenue that will cover costs, regulations may cause increases in the shift of milk production out of California.

Closing the extension gap: Information and communication technology in sustainable agriculture

As the information revolution sweeps through the agricultural sector, extension professionals may be lagging behind their clients in the use of information and communication technology (ICT) such as social media, which could be a valuable tool for outreach and education. We surveyed sustainable agriculture stakeholders in California — extension professionals, county agricultural commissioners, and members of farm bureaus and producer groups — to measure their ICT behavior and attitudes. Drawing on diffusion of innovation theory, we characterized the innovation attributes of ICT that may influence the adoption and use of new technology among extension professionals. We also studied their demographic characteristics to establish whether there was a connection with ICT use. The main perceived benefit of ICT was that it can quickly reach larger, more diverse and more distant audiences. The perceived challenges included lack of professional support, the potential for misinformation on social media platforms, and the time requirements and technical complexity of technology use. Extension professionals experienced these challenges more than other sustainable agriculture stakeholders, creating a technology gap between extension professionals and their clientele. An ICT community of practice and clear organizational guidelines for measuring and reporting performance relating to ICT might help extension professionals close the gap.

Broccoli meal fed to laying hens increases nutrients in eggs and deepens the yolk color

The nutritious stems and leaves of broccoli often go to landfills as byproducts after harvesting and processing of the florets. The stems and leaves contain specific carotenoids that are noted to have anti-allergic, anti-cancer and anti-obesity bioactivity. Research has shown the stems and leaves could be made into a meal, small amounts of which could be added to poultry diets to increase the nutrients in eggs and also deepen the color of the yolks. We studied adding a relatively high percentage (15%) of broccoli stem and leaves meal to the corn-soy diets of White Leghorn inbred crosses. Compared to the control group of hens, fed the unenhanced corn-soy diet, feed consumption, body weight, feed conversion, egg production, egg weight, albumen height, Haugh units and eggshell thickness were statistically similar. No harmful effects of the glucosinolates in broccoli were observed. Yolk color scores were significantly higher with the addition of the meal. The results justify larger studies with various commercial lines of laying hens and various levels of meal added to the diets.

News and Opinion

Research highlights

Recent articles from the Agricultural Experiment Station campuses and UC ANR's county offices, institutes and research and extension centers

Back on track? Reassessing rail transport for California's perishable produce

Moving perishable produce by rail, rather than by truck, could provide significant benefits for Californians.

Coordinated response to inadvertent introduction of pathogens to California restoration areas

Growers, regulators and native plant restoration experts are together trying to reduce the spread of more than 25 new Phytophthora taxa.