University of California Kearney Research and Extension Center

Parlier, CA, United States

University of California Kearney Research and Extension Center

Parlier, CA, United States
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Saito S.,U.S. Department of Agriculture | Michailides T.J.,University of California Kearney Research and Extension Center | Xiao C.L.,U.S. Department of Agriculture
Plant Disease | Year: 2016

Gray mold caused by Botrytis cinerea is a major postharvest disease of blueberry grown in the Central Valley of California and western Washington State. Sensitivities to boscalid, cyprodinil, fenhexamid, fludioxonil, and pyraclostrobin, representing five different fungicide classes, were examined for 249 (California) and 106 (Washington) B. cinerea isolates recovered from decayed blueberry fruit or flowers. In California and Washington, 7 and 17 fungicide-resistant phenotypes, respectively, were detected: 66 and 49% of the isolates were resistant to boscalid, 20 and 29% were moderately resistant to cyprodinil, 29 and 29% were resistant to fenhexamid, and 66 and 55% were resistant to pyraclostrobin. All isolates from California were sensitive to fludioxonil, whereas 70% of the isolates from Washington showed reduced sensitivity to fludioxonil. In California, 26 and 30% of the isolates were resistant to two and three classes of fungicides, respectively. In Washington, 31, 14, 16, and 9% of the isolates were resistant to two, three, four, and five classes of fungicides, respectively. Inherent risk of the development of resistance to quinone outside inhibitor (QoI) fungicides was assessed by detecting the presence of the Bcbi-143/144 intron in gene cytb. The intron was detected in 11.8 and 40% of the isolates in California and Washington, respectively, suggesting that the risk of QoI resistance is higher in California than in Washington. On detached blueberry fruit inoculated with 11 isolates exhibiting different fungicide-resistant phenotypes, most fungicides failed to control gray mold on fruit inoculated with the respective resistant phenotypes but the mixture of cyprodinil and fludioxonil was effective against all fungicide-resistant phenotypes tested. Our findings would be useful in designing and implementing fungicide resistance management spray programs for control of gray mold in blueberry. © 2017, American Phytopathological Society. All rights reserved.


Williams L.E.,University of California at Davis | Williams L.E.,University of California Kearney Research and Extension Center
Australian Journal of Grape and Wine Research | Year: 2010

Background and Aims: It is commonly thought that grapevine rootstocks vary in their tolerance to drought. This study examined the interaction between various applied water amounts and productivity of Cabernet Sauvignon grafted onto five rootstocks. Methods and Results: The commercial vineyard used in this study was located along the central coastof California. The rootstocks used were Teleki 5C, 110 Ricter, 140 Ruggeri, 1103 Paulson and Freedom. Irrigation amounts ranged from 0.25 up to 1.25 of estimated vineyard evapotranspiration. Midday leaf water potential (Yl), was significantly affected by irrigation treatment but not by rootstock. There was a significant effect of irrigation treatment and rootstock on berry weight, number of bunches per vine and yield but no interaction between those two factors. The rootstock 5C had the lowest yield compared with the other rootstocks. Yield at the 0.25 irrigation level was approximately 62% of the yield at the 1.25 irrigation level across rootstocks. Irrigation treatment was the only factor that significantly affected soluble solids in the fruit. There was a significant interaction between rootstock and irrigation amount on pruning weights. Berry weight, yield and pruning weights were linearly correlated with midday Yl across rootstock and year. Conclusions: The results indicate that the rootstocks producing greater yields at the highest applied water amounts also produced greater yields when deficit irrigated. Significance of the Study: Under both stressed and non-stressed conditions, the rootstocks with the highest yield were those with the greatest number of bunches. © 2010 Australian Society of Viticulture and Oenology Inc.


Williams L.E.,University of California at Davis | Williams L.E.,University of California Kearney Research and Extension Center
Irrigation Science | Year: 2012

A study was conducted in the San Joaquin Valley of California on Merlot to determine the interaction of applied water amounts [at 0.4, 0.8, and 1.2 of estimated vineyard evapotranspiration (ET c)] and leaf removal (at berry set or veraison) in the fruiting zone on productivity. Shaded area was measured beneath the canopy of the 1.2 irrigation treatment at solar noon throughout the study to provide an estimate of seasonal crop coefficients (K c). Vine water status was assessed across treatments and years by measuring midday leaf water potential (Ψ l). The maximum K c determined from the percent shaded area was 0.7 at the row spacing of 3.66 m and canopy type that developed a "California Sprawl." Irrigation treatment had a significant effect on midday Ψ l and no such effect for leaf removal. Clusters exposed to direct solar radiation had significantly higher temperatures and lower cluster Ψ than clusters in the shade. Irrigation treatment had a significant effect on berry weight, soluble solids, and titratable acidity. Yields of vines significantly increased as applied water amounts increased. In this wine grape production area, profitability is dependent upon yield. This study provided a reliable estimate of ET c and applied water amounts to maximize yield. © 2012 Springer-Verlag.


Williams L.E.,University of California at Davis | Williams L.E.,University of California Kearney Research and Extension Center
American Journal of Enology and Viticulture | Year: 2014

The effects of irrigation treatments with applied water amounts at various fractions of crop evapotranspiration (ETc) on productivity of Chardonnay grapevines grafted onto two rootstocks were determined across eight years. Irrigation treatments during the first four years were applied water amounts at 0.25, 0.5, 0.75, 1.0, and 1.25 of ETc while those in subsequent years were a no applied water treatment and applied water amounts at 0.5 and 1.0 of ETc. Grapevine water use was determined using the soil water balance method. Year had a significant effect on all measured parameters (berry weight, soluble solids, pH, titratable acidity, and yield and its components). The highest (21.9 t/ha) and lowest (11.6 t/ha) yields differed almost two-fold across years. While rootstock had a significant effect on some of the above parameters, they were not consistent among years and there were only a few instances in which there was a rootstock by irrigation interaction. Yield per unit applied water averaged 4.43 and 13.7 t/ML for the 1.25 and 0.25 irrigation treatments while yield per unit ETc averaged 4.28 and 6.45 t/ML for the 1.25 and 0.25 treatments, respectively. The high and low water footprint values per unit ETc ranged from 130 to 400 m3 of water/t across the duration of the study. The large difference in the water footprint from year to year was due to differences in yield. The water footprint for the no applied water treatment was 166 m3/t in 1998 and 228 m3/t in 1999. The fact that the water footprint reported here is lower than published values for grapevines may have been due to higher yields and better estimates of vineyard ETc. © 2014 by the American Society for Enology and Viticulture. All rights reserved.


Williams L.E.,University of California at Davis | Williams L.E.,University of California Kearney Research and Extension Center
American Journal of Enology and Viticulture | Year: 2014

A study was conducted in a Chardonnay vineyard located in the Carneros district of Napa Valley to derive vineyard evapotranspiration (ETc) and seasonal crop coefficients (Kc) values. The vineyard was planted on 2.13 m rows, using a vertical shoot-positioned trellis. Vineyard ETc was measured using the soil water balance method. Soil water content (SWC) was measured in one-fourth of an individual vine's soil profile (six access tubes per site) to a depth of 2.75 m. In addition, vines were irrigated with applied water amounts at 0.25, 0.5, 0.75, 1.0, and 1.25 of estimated vineyard ETc. Vineyard ETc the first year of the study was ~400 mm. Thereafter calculated vineyard Etc (the product of reference ET [ETo] and the Kc) ranged from 346 to 503 mm per season. Midday leaf water potential (Ψl), leaf net CO2 assimilation rate (A), and stomatal conductance (gs) were used to indirectly validate estimated Etc (to determine that vines were not stressed for water) and the derived Kc values. Midday Ψl, A, and gs were linearly related with applied water amounts and SWC across irrigation treatments and years. The diurnal measurements of A and gs resulted in differences among irrigation treatments, from early morning until late afternoon, with significant differences among treatments dependent upon actual applied water amounts. The results from this study are the first in which vineyard ETc has been measured on vines grown at a cool vineyard site in California. Estimates of ETc from this study would be valid for a vineyard with a row spacing of 2.13 m and a canopy vertically positioned using a maximum Kc of 0.74. © 2014 by the American Society for Enology and Viticulture. All rights reserved.


Avenot H.F.,University of California Kearney Research and Extension Center | Michailides T.J.,University of California Kearney Research and Extension Center
Crop Protection | Year: 2010

Succinate dehydrogenase (Complex II or succinate-ubiquinone oxidoreductase) is the smallest complex in the respiratory chain and transfers the electrons derived from succinate directly to the ubiquinone pool. Succinate dehydrogenase inhibitor (SDHI) fungicides specifically inhibit fungal respiration by blocking the ubiquinone-binding sites in the mitochondrial complex II and play an important role in the integrated management programmes of many plant diseases. In contrast to first generation of SDHI fungicides (e.g. carboxin) exceptionally active against basidiomycetes, newer active ingredients in this class (e.g. boscalid, penthiopyrad, fluopyram) show a broad-spectrum activity against various fungal species. However, the consistent use of site-specific fungicides such as SDHIs can result in the selection of resistant fungal genotypes which may ultimately lead to a rapid decline of fungicide performance. This paper reviews previous and recent advances in understanding the molecular mechanisms and other factors controlling the evolution of resistance to SDHI fungicides. Furthermore, we provide recommendations on the future use of new developed molecules of this group as well as future research prospects. © 2010 Elsevier Ltd.


Williams L.E.,University of California Kearney Research and Extension Center
Australian Journal of Grape and Wine Research | Year: 2012

Aims: To determine the effects of applied water amounts at various fractions (0.2, 0.6, 1.0 and 1.4) of grapevine evapotranspiration on leaf gas exchange of Thompson Seedless grapevines. Methods and Results: Midday stomatal conductance (g s) decreased linearly as leaf water potential (Ψ l) and soil water content decreased. Leaf net CO 2 assimilation rate only decreased once midday Ψ l values were less than -1.0MPa and when ~50% of the soil water content at field capacity had been depleted. The mean seasonal midday A/g s ratio (intrinsic water use efficiency) was greatest for the 0.2 irrigation treatment and decreased as applied water amounts increased. Diurnal A and g s for vines irrigated at the 0.6 level or greater reached a maximum prior to midday remained constant thereafter before decreasing late in the afternoon, while those for vines that received less water decreased subsequent to the first measurement of the day. Conclusions: A and g s responded differently to vine and soil water statuses under the conditions of this study. There was no midday depression in either A or g s for vines irrigated at full evapotranspiration. Significance of the Study: The values of Ψ l, A and g s reported here would serve as criteria to indicate that vines were well watered. © 2012 Australian Society of Viticulture and Oenology Inc.


Williams L.E.,University of California Kearney Research and Extension Center
Journal International des Sciences de la Vigne et du Vin | Year: 2012

Aims: Leaf (Ψ1) and stem (Ψstem) water potentials were measured on grapevines to determine the effects of shoot location on both methods to assess vine water status. Methods and results: Cabernet-Sauvignon and Merlot used in this study were grown at two locations in California. Measurements were taken at midday in July (Merlot) and at two times of the day (morning and afternoon), on two dates in August (Cabernet-Sauvignon). Measurements of Ψl and Ψstem, stomatal conductance and transpiration were taken on shoots entirely exposed to direct solar radiation or on shoots totally in the shade at the times of measurement. There were significant differences (P < 0.05) between Ψl and/or Ψstem measured on shoots exposed to direct solar radiation and those in the shade. Both Ψl and Ψstem were significantly greater on the shoots exposed to direct sunlight compared to those in the shade. There was no significant difference between Ψl measured on shaded leaves and Ψstem determined on the fully exposed shoots. Conclusions: Regardless of method used, water potentials were highly correlated with stomatal conductance measured on leaves in direct sunlight at the same time. All means of measuring grapevine water potential used in this study were highly correlated with one another. Significance and impact of the study: The data indicate that any of the techniques used in this study would be a sensitive indicator of vine water status and that the Ψ of shaded leaves would be an alternative to the measurement of Ψstem. © Vigne et Vin Publications Internationales.


Grantz D.A.,University of California Kearney Research and Extension Center
Journal of Cotton Science | Year: 2016

Ozone (O3) is a secondary atmospheric pollutant that causes widespread damage to vegetation, including cotton. The high temperatures and abundant sunlight that lead to good cotton yields also lead to production of O3. The early crop loss experiments of the 1970s identified upland cotton as particularly sensitive to O3. Exposure to ambient concentrations of O3 resulted in a 10 to >15% loss in economic yield. More recent experiments with modern cultivars have confirmed damage to upland and Pima cultivars but have not assessed yield loss under agronomic conditions. It is likely that selection for yield in high O3 environments has led to inadvertent selection for tolerance to O3. Ozone reduces yield and fiber quality, mediated by O3-induced changes in gross photosynthesis, respiration, and translocation of current photosynthate out of source leaves. Ozone typically reduces root development and the root-to-shoot biomass ratio, which has secondary effects on plant growth and development and on water relations. Ozone also reduces stomatal conductance as a primary defense against entry of O3 into the plant, but this also restricts entry of CO2 and therefore photosynthesis. Ozone is clearly phytotoxic and impacts cotton as well as other species. Recent research has led to understanding many aspects of the mechanism of O3 damage and could lead to targeted approaches to improving O3 tolerance, and therefore, yield in O3-impacted production areas. © The Cotton Foundation 2016.


Brewer M.J.,Texas A&M University-Corpus Christi | Goodell P.B.,University of California Kearney Research and Extension Center
Annual Review of Entomology | Year: 2012

Agricultural, environmental, and social and policy interests have influenced integrated pest management (IPM) from its inception. The first 50 years of IPM paid special attention to field-based management and market-driven decision making. Concurrently, IPM strategies became available that were best applied both within and beyond the bounds of individual fields and that also provided environmental benefits. This generated an incentives dilemma for farmers: selecting IPM activities for individual fields on the basis of market-based economics versus selecting IPM activities best applied regionally that have longer-term benefits, including environmental benefits, that accrue to the broader community as well as the farmer. Over the past several decades, public-supported incentives, such as financial incentives available to farmers from conservation programs for farms, have begun to be employed to encourage use of conservation techniques, including strategies with IPM relevance. Combining private investments with public support may effectively address the incentives dilemma when advanced IPM strategies are used regionally and provide public goods such as those benefiting resource conservation. This review focuses on adaptation of IPM to these broader issues, on transitions of IPM from primarily individual field-based decision making to coordinated community decision making, and on the form of partnerships needed to gain long-lasting regional and environmental benefits. © 2012 by Annual Reviews. All rights reserved.

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