Larson-Praplan S.,University of California Cooperative Extension
Rangelands | Year: 2014
On the Ground Spanish colonists brought cattle to California when they landed in San Diego in 1769, with two hundred head of cattle arriving by overland routes. Mexico, achieving independence, established rules to petition for land grants in California, paving the way for additional settlers by making land grants easier to obtain. The Gold Rush resulted in cattle numbers quadrupling and sheep numbers increasing more than 60-fold between 1850 and 1860. Multiple uses, such as agriculture crop production, impacted California rangelands. Public policies now influence management of approximately 38 million acres of privately and publicly owned rangelands. © 2014 by the Society for Range Management.
Costello M.J.,University of California Cooperative Extension
HortScience | Year: 2010
Nodding needlegrass [Nassella cernua (Stebbins & R.M. Love) Barkworth], a California native perennial grass, was tested for its effects on grapevine and soil-water relations in a drip-irrigated vineyard in Parlier, CA. Vine water status and in-row and between-row soil moisture (at 0.3 m, 0.6 m, 0.9 m, 1.2 m, and 1.5 m) were monitored semiweekly from June to September. There was no overall significant difference in leaf water potential between treatments. In-row soil moisture was lowest at depths of 0.6 m to 0.9 m within the nodding needlegrass treatment but was lowest from 0.3 m to 0.9 m within the clean cultivation treatment. Compared with clean cultivation, nodding needlegrass in-row soil moisture was significantly higher at depths of 0.3 m and 0.6. m and did not differ at depths of 0.9 m and 1.2 m. In contrast, in-row soil moisture was significantly higher under clean cultivation compared with nodding needlegrass at 1.5 m. Betweenrow soil moisture was significantly higher under clean cultivation compared with nodding needlegrass at every depth. Combining in-row and between-row data, overall vineyard soil moisture was slightly lower, by 1.2% points, in the nodding needlegrass treatment compared with clean cultivation. There was no interaction between treatment and depth for between-row soil moisture, indicating that the vines used little water from the between-row area. The lack of difference between treatments in the rate of soil moisture depletion over the season indicates that nodding needlegrass used little water during the summer. Based on these results, nodding needlegrass appears to be suitable as a permanent cover crop in California drip-irrigated vineyards where competition for summer water is a concern.
Alexander J.,University of California Cooperative Extension
Environmental Management | Year: 2010
Sudden Oak Death has been impacting California's coastal forests for more than a decade. In that time, and in the absence of a centrally organized and coordinated set of mandatory management actions for this disease in California's wildlands and open spaces, many local communities have initiated their own management programs. We present five case studies to explore how local-level management has attempted to control this disease. From these case studies, we glean three lessons: connections count, scale matters, and building capacity is crucial. These lessons may help management, research, and education planning for future pest and disease outbreaks. © 2010 The Author(s).
Espino L.,University of California Cooperative Extension
Florida Entomologist | Year: 2012
Field experiments were conducted during 2009 and 2010 on commercial rice fields in the Sacramento Valley of California to validate observations regarding the prevalence of immature populations of the rice water weevil, Lissorhoptrus oryzophilus Kuschel (Coleoptera: Curculionidae), near field borders, and to assess their impact on yield. In 5 commercial fields, insecticide-treated and untreated plots were established 4.5, 30 and 60 m from one edge of the field. Soil core samples were collected on 2 dates and inspected for L. oryzophilus immatures. Rice yields were determined by harvesting 15 m2 plots in 2009 or 1 m2 per plot in 2010. Analysis of variance (ANOVA) showed that in most locations, immature populations were higher in plots 4.5 or 30 m from the field's edge than in plots 60 m from the field's edge. Yields from treated and untreated plots did not differ significantly. Linear regression of immature populations and rice grain yield per plot per location did not yield a significant, inverse density-yield relationship. Results indicate that border applications of insecticides for L. oryzophilus management are appropriate; however, growers are advised to inspect their fields to confirm border populations and effects on yield. Research needs regarding sampling and economic thresholds are discussed.
Enfield R.P.,University of California Cooperative Extension
New directions for youth development | Year: 2013
This article reports on experiences and methods of adapting a valid adult social capital assessment to youth audiences in order to measure social capital and sense of place. The authors outline the process of adapting, revising, prepiloting, piloting, and administering a youth survey exploring young people's sense of community, involvement in the community, and the development of social capital. They then discuss the trade-offs of defining the often amorphous concepts included in social capital as they select measurement scales. The constructs used in the survey are agency, belonging, engagement, and trust for bonding, bridging, and linking forms of social capital. Copyright © 2013 Wiley Periodicals, Inc., A Wiley Company.
Koike S.T.,University of California Cooperative Extension
Plant Disease | Year: 2013
Mexican sunflower (Tithonia rotundifolia) is a plant in the Asteraceae that is grown commercially as a cutflower commodity and also as a beneficial insectary plant. In June 2012 in coastal California (Santa Cruz County), several fields of organic lettuce (Lactuca sativa) were interplanted with direct-seeded rows of Mexican sunflower (cv. Torch) in order to attract beneficial insects. When approximately 2 to 3 weeks from harvest, lettuce plants began to wilt and collapse. Lettuce crowns were decayed and covered with white mycelium and small (0.5 to 3 mm diameter), irregularly shaped, black sclerotia. These plants were confirmed to have lettuce drop disease caused by Sclerotinia minor (2). In addition, Mexican sunflower plants began to wilt and eventually died. Initial symptoms on crowns and bases of the main stems in contact with soil consisted of a light tan discoloration. These discolored areas turned darker brown, became necrotic, and later were covered with white mycelium and sclerotia that were identical to those found on lettuce. Symptomatic sunflower stems were surface disinfested and small pieces from the margins of necrotic areas were placed into petri plates containing acidified potato dextrose agar. Resulting fungal colonies were white, produced profuse numbers (approx. 39 sclerotia/cm2) of small black sclerotia, and were identified as S. minor. Six-week-old Mexican sunflower plants grown in a peat moss-based rooting medium in 5-cm square pots were used to test the pathogenicity of four isolates. Isolates were grown on cubed and autoclaved potato pieces and resulting sclerotia were recovered and dried (1). For each isolate, 12 plants for each of three cultivars (cvs. Fiesta del Sol, Torch, and Yellow Torch) were inoculated by placing 3 to 5 sclerotia 1 cm below the soil level and adjacent to the plant crowns/stem bases. Sterile sand was placed next to crowns of the control plants. Plants were maintained in a greenhouse at 22 to 24°C. Symptom development was rapid and after 6 to 7 days, inoculated Tithonia plants exhibited brown necrosis at inoculated areas. After 10 days, Tithonia crowns were decayed and plants wilted. S. minor was reisolated from selected necrotic crown and stem tissues. Diseased plants that were not used for reisolations later supported the growth of the characteristic white mycelium and black sclerotia. There were no significant differences between the Tithonia cultivars, and overall disease incidence ranged from 74 to 100%. Non-inoculated plants were asymptomatic. The experiment was repeated and results were similar. In addition, the sclerotia of the four Tithonia isolates were similarly inoculated onto sets of 12 romaine lettuce plants (cv. Green Towers). After 5 to 6 days, all plants developed lettuce drop disease and the pathogen was reisolated. To my knowledge, this is the first report of Mexican sunflower as a host of S. minor. These findings indicate that Mexican sunflower and lettuce are susceptible to the same lettuce drop pathogen, and that this beneficial insectary plant could increase soilborne inoculum of S. minor. Growers should therefore be aware of the host status of beneficial insectary and other plants interplanted with crops. © The American Phytopathological Society.
Molinar R.H.,University of California Cooperative Extension
HortScience | Year: 2012
Sinqua and moqua, better known as Luffa actuangula and Benincasa hispida var. chiehgua, are but a few of the 70 or so Asian vegetables being grown in Fresno, CA. These little-known vegetables are very common to the 1300 Hmong, Mien, Lao, and Chinese farmers growing them for the specialty and wholesale markets in Fresno. This article discusses 24 Asian vegetables commonly grown on farms and sold to more than a dozen specialty crop packing houses in Fresno and at farmers markets in California. Cultural information, pest problems, and culinary uses are also briefly discussed.
Battany M.C.,University of California Cooperative Extension
Agricultural and Forest Meteorology | Year: 2012
Upward-blowing wind machines have been commercialized for use in frost protection but little quantitative information exists regarding how their operation alters site temperatures. In particular, their performance relative to conventional wind machines has been debated. To address this need, experiments were conducted on 12 spring frost nights in 2010 and 2011 in a commercial winegrape vineyard where either two upward-blowing wind machines or a single conventional wind machine were operated. Comprehensive measurements of air temperature changes caused by wind machine operation were evaluated on multiple transects at heights of 1.1, 4, 7 and 10m. All 12 frost nights were characterized by low wind and clear sky conditions, with temperature inversion strengths commonly associated with beneficial wind machine use occurring on 9 of the 12 nights. The operation of the conventional wind machine produced consistently larger and more statistically significant increases in temperature, particularly at the 1.1m vine level, as compared to the operation of the upward-blowing wind machines which produced very minor increases in temperature at the 1.1m level under strong inversion conditions and either no change or decreases in temperature under weaker inversion conditions. Based on the summary relationships between temperature changes as a function of inversion strength, under conditions of an inversion gradient of 0.2°Cm -1 the conventional wind machine would be expected to raise target area temperatures by 1.6°C at the vine level, while the upward-blowing wind machines would have no net effect under the same inversion conditions. Smoke tracking of the air flow from the upward-blowing wind machines indicated that the air jet reached 25m height, and then tended to slowly settle back towards the ground. These results indicate relatively poor performance of this type of low-powered (6.3kW) upward-blowing wind machine compared to a conventional wind machine under the conditions of this study. © 2012 Elsevier B.V..
Bilodeau G.J.,636 East Alisal St. |
Koike S.T.,University of California Cooperative Extension |
Uribe P.,636 East Alisal St. |
Martin F.N.,636 East Alisal St.
Phytopathology | Year: 2012
Verticillium dahliae is responsible for Verticillium wilt on a wide range of hosts, including strawberry, on which low soil inoculum densities can cause significant crop loss. Determination of inoculum density is currently done by soil plating but this can take 6 to 8 weeks to complete and delay the grower's ability to make planting decisions. To provide a faster means for estimating pathogen populations in the soil, a multiplexed TaqMan real-time polymerase chain reaction (PCR) assay based on the ribosomal DNA (rDNA) intergenic spacer (IGS) was developed for V. dahliae. The assay was specific for V. dahliae and included an internal control for evaluation of inhibition due to the presence of PCR inhibitors in DNA extracted from soil samples. An excellent correlation was observed in regression analysis (R2 = 0.96) between real-time PCR results and inoculum densities determined by soil plating in a range of field soils with pathogen densities as low as 1 to 2 microsclerotia/g of soil. Variation in copy number of the rDNA was also evaluated among isolates by SYBR Green real-time PCR amplification of the V. dahliaespecific amplicon compared with amplification of several single-copy genes and was estimated to range from ?24 to 73 copies per haploid genome, which translated into possible differences in results among isolates of ?1.8 cycle thresholds. Analysis of the variation in results of V. dahliae quantification among extractions of the same soil sample indicated that assaying four replicate DNA extractions for each field sample would provide accurate results. A TaqMan assay also was developed to help identify colonies of V. tricorpus on soil plates. © 2012 The American Phytopathological Society.
Cloyd R.A.,Kansas State University |
Bethke J.A.,University of California Cooperative Extension
Pest Management Science | Year: 2011
The neonicotinoid insecticides imidacloprid, acetamiprid, dinotefuran, thiamethoxam and clothianidin are commonly used in greenhouses and/or interiorscapes (plant interiorscapes and conservatories) to manage a wide range of plant-feeding insects such as aphids, mealybugs and whiteflies. However, these systemic insecticides may also be harmful to natural enemies, including predators and parasitoids. Predatory insects and mites may be adversely affected by neonicotinoid systemic insecticides when they: (1) feed on pollen, nectar or plant tissue contaminated with the active ingredient; (2) consume the active ingredient of neonicotinoid insecticides while ingesting plant fluids; (3) feed on hosts (prey) that have consumed leaves contaminated with the active ingredient. Parasitoids may be affected negatively by neonicotinoid insecticides because foliar, drench or granular applications may decrease host population levels so that there are not enough hosts to attack and thus sustain parasitoid populations. Furthermore, host quality may be unacceptable for egg laying by parasitoid females. In addition, female parasitoids that host feed may inadvertently ingest a lethal concentration of the active ingredient or a sublethal dose that inhibits foraging or egg laying. There are, however, issues that require further consideration, such as: the types of plant and flower that accumulate active ingredients, and the concentrations in which they are accumulated; the influence of flower age on the level of exposure of natural enemies to the active ingredient; the effect of neonicotinoid metabolites produced within the plant. As such, the application of neonicotinoid insecticides in conjunction with natural enemies in protected culture and interiorscape environments needs further investigation. © 2010 Society of Chemical Industry.