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Forest fires produce malodorous phenols, bioaccumulated in grapes as odorless phenol glycosides (mono- to tri-), and produce unpleasant

A field study was conducted for three consecutive seasons in the hot climate of central California to assess the performance of ‘Merlot’ grapevine (Vitis vinifera) grafted onto ‘Freedom’ [Fresno 1613-59 × Dog Ridge 5 (27% V. vinifera hybrid)] during training system conversion to facilitate mechanization. The traditional head-trained and cane-pruned (CP) system was either retained or converted either to a bilateral cordon-trained, spur-pruned California sprawl training system (HP), or to a bilateral cordon-trained, mechanically box-pruned single high-wire sprawling system (SHMP). After the conversion, SHMP sustained greater yield with more clusters per vine and smaller berries without affecting the canopy microclimate. This was due to a higher number of nodes retained after dormant pruning. The SHMP canopies, compared with CP and HP; filled allotted canopy space earlier based on photosynthetically active radiation (PAR) transmitted through the canopies, populating the space allotted per vine, favoring higher production efficiency. There were no adverse effects of training systems on berry composition or flavonoid concentration, during or after conversion to mechanical management. However, experimental year effect was obvious on anthocyanin composition of ‘Merlot’ berries, increasing trihydroxylated (i.e., delphinidin-based) anthocyanins in the latter years of the experiment. Our results also provided evidence that earlier canopy growth coupled with sufficient reproductive compensating responses allowed for increased yields while reaching commercial maturity without a decline in anthocyanin content with the SHMP. Converting CP to SHMP reduced labor operations costs by 90%. Furthermore, the SHMP had greater gross revenue and resulted in greater net income per acre even when the conversion year was taken into account. Therefore, SHMP is recommended for growers within the hot climate of the central San Joaquin Valley as a means to maintain productivity of vineyards while not sacrificing berry composition at the farm gate.

Studies have shown that vegetational diversity in or around cropping systems can enhance natural enemy abundance, although the impact on herbivores is less certain. We studied the influence of vineyard vegetational borders on density of the western grape leafhopper, Erythroneura elegantula, its major parasitoids, Anagrus spp., and two generalist predators, Orius spp. and Leptothrips mali. Two study vineyards had planted, perennial flowering hedgerows, one bordered a natural riparian zone, and one had a sparse border of native trees. From April to September 2007, we counted leafhopper nymphs and adults of Anagrus spp., Orius spp. and L. mali within 10 m of the border, and at additional 20 m intervals up to 90 m. At two sites with a diverse border, leafhopper density was stable nearest the border; at other distances leafhopper density decreased between the first and second generations. This effect was not seen at the sparse border site. Anagrus spp. density was enhanced at one site with a diverse border, but only late season. There was no border effect on the generalist insect predators, by site or early vs. late season. Regression analysis showed a positive relationship between leafhopper and Anagrus spp. density, suggesting that the parasitoids were responding to higher leafhopper density. We conclude that, depending on the nature of the border vegetation, there can be an effect on leafhopper nymphal density, but in this study there is no evidence that it was due to natural enemies.

Urbez-Torres, J. R., Battany, M., Bettiga, L. J., Gispert, C., McGourty, G., Roncoroni, J., Smith, R. J., Verdegaal, P., and Gubler, W. D. 2010. Botryosphaeriaceae species spore-trapping studies in California vineyards. Plant Dis. 94:717-724. The seasonal abundance of Botryosphaeriaceae spp. spores was studied in California vineyards by using glass microscope slides covered with petroleum jelly placed on grapevine cordons and Burkard volumetric spore traps at seven and two different locations, respectively. Correlation analysis was used to determine which meteorological variables (precipitation, relative humidity, temperature, and wind speed) influenced Botryosphaeriaceae spp. spore release. Among all variables, regression analysis resulted in a strong relationship between spore release and precipitation. Additionally, a positive relationship between irrigation and spore release was also observed in the Riverside County vineyard. During the study period, spore discharge of Botryosphaeriaceae spp. occurred from the first fall rain through the last spring rains, coinciding with September to April. However, based on the results obtained from the spore traps, most spores (over 60%) were trapped following rain events during the winter months of December, January, and February, which coincides with the grapevine pruning season. Botryosphaeriaceae spp. spore release was much lower in fall and early spring (22%) and very few or no spores were trapped in late spring and summer (3%). This work suggests that a delay of pruning time in California may be warranted to reduce grapevine infection because the current timing coincides with the greatest period of spore discharge.

Pest and disease pressures have traditionally driven the use of grapevine rootstocks. However, with competing demands on limited water resources and changing climate conditions, the water available for agriculture will likely continue to diminish. This inevitability has resulted in an increased interest in grape rootstock effects on scion growth, specifically yield components, as a function of parentage and in terms of drought tolerance. It has also spurred efforts to breed new rootstocks with combined pest, disease, and abiotic stress resistance. Field studies examining rootstock effect on scion growth and development have been inconsistent due to complications associated with varying soil types and weather factors unique to each site. Other factors tend to vary from site to site including trellising systems, scion cultivar selection and management practices, each of which also has a role in determining vine phenology. Due to these issues, rootstock trial data is often presented on a site-by-site basis with the objective of determining if a specific rootstock tends to yield more or less than other rootstocks on a given site. Although inherently limited by the aforementioned challenges, rootstock trails are arguably one of the best methods of providing insight into rootstock performance and scion interactions. The Wolpert rootstock trails in California were one of the more comprehensive efforts to understand and classify rootstock performance as a function of site. General trends in performance were observed as a function of rootstock selection with regard to yield and pruning weights.

A relatively high percentage of epiphytic bacteria on pear leaf and fruit surfaces had the ability to produce indole-3-acetic acid (IAA) in culture media supplemented with tryptophan. While over 50% of the strains produced at least small amounts of IAA in culture, about 25% of the strains exhibited high IAA production as evidenced by both colorimetric and high-performance liquid chromatography analysis of culture supernatants. A majority of the strains that produced high amounts of IAA were identified as Erwinia herbicola (Pantoea agglomerans), while some strains of Pseudomonas syringae, Pseudomonas viridiflava, Pseudomonas fluorescens, Pseudomonas putida, and Rahnella aquaticus that produced high amounts of IAA also were found on pear. Fruit russeting was significantly increased in 39 out of 46 trials over an 8-year period in which IAA-producing bacteria were applied to trees compared with control trees. A linear relationship was observed between fruit russet severity and the logarithm of the population size of different IAA-producing bacteria on trees in the 30 days after inoculation, when normalized for the amount of IAA produced by each strain in culture. On average, the severity of fruit russet was only about 77% that on control trees when trees were treated at the time of bloom with Pseudomonas fluorescens strain A506, which does not produce IAA. Both total bacterial populations on pear in the 30-day period following full bloom and fruit russet severity varied greatly from year to year and in different commercial orchards over a 10-year period. There was a strong linear correlation between the logarithm of total bacterial population sizes and fruit russet severity.

In a replicated study conducted from 1990 to 1992, cover crops and a control (resident vegetation) were evaluated in an organic wine-grape vineyard (cv. ‘Chardonnay’), located at a valley floor site in Hopland, Mendocino County, California. The purpose was to assess plant phenology, stature, biomass production, competitiveness with resident vegetation, and second-year stand regeneration or persistence in an unfilled vineyard. Legumes (Fabaceae) evaluated included nine annual and two perennial types of clover (Trifolium spp.), bell bean and three other types of Vicia, two types of coolseason annual medic (Medicago spp.), field pea (Pisum sativum ssp. arvense), a mixture of biennial sweetclovers (Melilotus alba and M. officinalis), broadleaf birdsfoot trefoil (Lotus comiculatus). There were six types of cool-season annual grasses (Poaceae) including three cereal grains. Native Californian perennial grasses included one rhizomatous and five bunch types. The sole representative of Brassicaceae was bl...

Background Quantification of ecosystem services, such as carbon (C) storage, can demonstrate the benefits of managing for both production and habitat conservation in agricultural landscapes. In this study, we evaluated C stocks and woody plant diversity across vineyard blocks and adjoining woodland ecosystems (wildlands) for an organic vineyard in northern California. Carbon was measured in soil from 44 one m deep pits, and in aboveground woody biomass from 93 vegetation plots. These data were combined with physical landscape variables to model C stocks using a geographic information system and multivariate linear regression. Results Field data showed wildlands to be heterogeneous in both C stocks and woody tree diversity, reflecting the mosaic of several different vegetation types, and storing on average 36.8 Mg C/ha in aboveground woody biomass and 89.3 Mg C/ha in soil. Not surprisingly, vineyard blocks showed less variation in above- and belowground C, with an average of 3.0 and 84.1 Mg C/ha, respectively. Conclusions This research demonstrates that vineyards managed with practices that conserve some fraction of adjoining wildlands yield benefits for increasing overall C stocks and species and habitat diversity in integrated agricultural landscapes. For such complex landscapes, high resolution spatial modeling is challenging and requires accurate characterization of the landscape by vegetation type, physical structure, sufficient sampling, and allometric equations that relate tree species to each landscape. Geographic information systems and remote sensing techniques are useful for integrating the above variables into an analysis platform to estimate C stocks in these working landscapes, thereby helping land managers qualify for greenhouse gas mitigation credits. Carbon policy in California, however, shows a lack of focus on C stocks compared to emissions, and on agriculture compared to other sectors. Correcting these policy shortcomings could create incentives for ecosystem service provision, including C storage, as well as encourage better farm stewardship and habitat conservation.

Plots were established at Ukiah and Davis, California, and Medford and Hood River, Oregon, to evaluate the effect of fenarimol (Rubigan 1 EC), applied at various stages of bloom development, on fruit shape of Bartlett pear. At each location, 10 different treatment schedules were applied at various combinations of bud burst (BB), green cluster (GC), white bud (WB), and full bloom (FB). In schedules that included an application at FB, the fruit length:diameter (L/D) ratio was significantly reduced in at least three of four locations when compared to untreated controls. When fenarimol was applied at BB, GC, WB, and FB, the L/D ratio was reduced at all locations. Treatment at BB only did not affect L/D ratio. Schedules involving GC or WB, but not FB, resulted in reduced L/D ratios at only one or two locations. When data from all four locations were combined, L/D ratios were significantly reduced by all fenarimol treatments except BB alone, and the smallest L/D ratios resulted from treatments which included applications at both WB and FB. Fruit stem length was significantly reduced by all timings of fenarimol application except GC at Medford, and all timings except BB and GC at Ukiah. Fruit weight did not differ among treatments.

Pseudomonas fluorescens strain A506 and the antibiotics streptomycin and oxytetracycline, to which this antagonist is resistant, were evaluated individually and in combination in field trials over a 16-year period to assess the interactions and relative efficacy of bactericides and antagonistic bacteria in the control of fire blight and frost injury to pear. Strain A506 maintained population sizes of greater than about 10 5 cells per fruiting spur for over 30 days on trees inoculated once with this strain. Over 90% of the flowers on inoculated trees harbored detectable populations of strain A506. The population sizes of strain A506 were as high on inoculated trees, to which streptomycin was applied, as on trees sprayed only with strain A506. The population sizes of ice nucleation active bacteria were about 100-fold lower on trees treated with strain A506 than on untreated control trees or trees sprayed only with antibiotics. The incidence of frost injury to pear fruit in natural frosts and of fire blight was reduced to about 40 and 50%, respectively, of that on untreated trees. The incidence of frost damage and fire blight was lower on trees treated both with strain A506 and antibiotics than with either agent alone. Strain A506 and antibiotics acted additively in the control of frost and disease.