Rhonda J. Smith

Botryosphaeriaceae Species Spore-Trapping Studies in California Vineyards

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.

Priority risk factors for back injury in agricultural field work: vineyard ergonomics

ABSTRACT With support of a NIOSH Community Partners grant, the authors reviewed data from three cooperating vineyard companies in Napa and Sonoma Counties, finding both high rates of evidence of musculoskeletal disorders (MSDs) and identifying priority MSD hazards for intervention. Data from OSHA 200 injury report logs identified 29 reported MSDs and 435 lost workdays in a working population of 194 in a 30-month period. The majority of these (20) involved backstrain. High risk job tasks were identified, including: employer-identified tasks, analysis of injury reports, and ergonomics risk factor checklist survey of task work. Triangulating across these three data groups resulted in identification of high priority tasks, including: hand harvest work, hand pruning, and weeding using shovels. Priority risk factors for back injury in these jobs were: repetitive lifting of heavy loads, repetitive exertion of force by the trunk and upper extremities, and repetitive or sustained awkward postures of the trunk (including full stoop and twisting with loads).

Reducing the Economic Impact of Grapevine Leafroll Disease in California: Identifying Optimal Disease Management Strategies

Grapevine leafroll disease (GLRD) is a devastating viral disease found across all grapegrowing regions. Vineyard managers have adopted various strategies for managing GLRD, including roguing individual symptomatic vines and replacing them with certified vines derived from clean, virus-tested stocks; applying insecticides targeting mealybug vector populations to reduce disease spread and minimize long-term impacts; and fully replanting vineyards at the onset of disease symptoms. Moreover, some managers elect not to control GLRD at all. We collected survey data from vineyard managers throughout the three major California grapegrowing counties, Napa, Sonoma, and Northern San Joaquin Valley, to estimate the economic impact of GLRD on Cabernet Sauvignon vines. The goal was to identify cost-minimizing management strategies under various disease-prevalence levels, price penalties, timing of disease onset relative to vineyard age, yield losses, and costs of control. Our results estimated that the economic cost of GLRD ranged from

Red blotch disease alters grape berry development and metabolism by interfering with the transcriptional and hormonal regulation of ripening

29,902 to

Mitigating the Economic Impact of Grapevine Red Blotch: Optimizing Disease Management Strategies in U.S. Vineyards

226,405 per ha. Roguing symptomatic vines and replanting with certified vines in combination with insecticides to reduce mealybugs may minimize losses if GLRD prevalence is low (between 5 and 10%), while a full vineyard replacement should be pursued if disease prevalence is higher, generally above 25%, although regional differences were noted. These findings should help vineyard managers in the three regions examined to adopt optimal GLRD management strategies that can be tailored regionally or locally to unique market opportunities, potential market prices, and annual operating costs.

The effect of paclobutrazol injected into the soil on vegetative growth and yield of Vitis vinifera L., cv. Thompson Seedless

&NA; Grapevine red blotch‐associated virus (GRBaV) is a major threat to the wine industry in the USA. GRBaV infections (aka red blotch disease) compromise crop yield and berry chemical composition, affecting the flavor and aroma properties of must and wine. In this study, we combined genome‐wide transcriptional profiling with targeted metabolite analyses and biochemical assays to characterize the impact of the disease on red‐skinned berry ripening and metabolism. Using naturally infected berries collected from two vineyards, we were able to identify consistent berry responses to GRBaV across different environmental and cultural conditions. Specific alterations of both primary and secondary metabolism occurred in GRBaV‐infected berries during ripening. Notably, GRBaV infections of post‐véraison berries resulted in the induction of primary metabolic pathways normally associated with early berry development (e.g. thylakoid electron transfer and the Calvin cycle), while inhibiting ripening‐associated pathways, such as a reduced metabolic flux in the central and peripheral phenylpropanoid pathways. We show that this metabolic reprogramming correlates with perturbations at multiple regulatory levels of berry development. Red blotch caused the abnormal expression of transcription factors (e.g. NACs, MYBs, and AP2‐ERFs) and elements of the post‐transcriptional machinery that function during red‐skinned berry ripening. Abscisic acid, ethylene, and auxin pathways, which control both the initiation of ripening and stress responses, were also compromised. We conclude that GRBaV infections disrupt normal berry development and stress responses by altering transcription factors and hormone networks, which result in the inhibition of ripening pathways involved in the generation of color, flavor, and aroma compounds.

Evaluation of Pruning Wound Susceptibility and Protection Against Fungi Associated with Grapevine Trunk Diseases

Grapevine red blotch disease (GRBD) is a recently-recognized viral disease found across some of the major grapegrowing regions in the United States. Vineyard managers were surveyed to (i) estimate the economic impact of GRBD on Vitis vinifera cv. Cabernet Sauvignon in Napa and Sonoma Counties in California and on V. vinifera cv. Merlot in eastern Washington and Long Island in New York, and (ii) to identify cost-minimizing management strategies under various disease incidence rates, price penalties for suboptimal fruit composition, timing of disease onset relative to vineyard age, and costs of control. The economic cost of GRBD was estimated to range from

Mulched cover crops as an alternative to conventional weed management systems in vineyards

2213/ha in eastern Washington, when disease onset occurs at a low initial infection level and there is a low price penalty, to

Effect of interior canopy defoliation on berry composition and potassium distribution in Thompson seedless grapevines

68,548/ha in Napa County, when initial infection rates and quality penalties are both high. Our results further suggest that roguing symptomatic vines and replanting with clean vines derived from virus-tested stocks minimize losses if GRBD incidence is low to moderate (below 30%), while a full vineyard replacement should be pursued if disease incidence is higher, generally above 30%. These findings should help vineyard managers in the four examined viticultural regions adopt optimal GRBD management strategies.

Inception, Progression, and Compositional Consequences of a Berry Shrivel Disorder

SummaryGrapevines, cv. Thompson Seedless were treated with the plant growth regulator paclobutrazol in the spring of 1984. The treatments consisted of four soil application rates (including a zero control) of paclobutrazol on two phenological dates (budbreak and bloom). Vegetative growth, as measured by pruning weight, vine yield and fruit maturity characteristics, were determined in 1984 and in the next three growing seasons. There was no significant difference in vine yield between treatments at harvest in 1984; however, the fruit of vines receiving paclobutrazol at budbreak had accumulated less sugar at that time. Paclobutrazol application significantly (P < 0.01 ) reduced pruning weights in 1984 for all vines receiving paclobutrazol. Only the highest rate of paclobutrazol significantly reduced pruning weights in 1985. The number of clusters per vine and yield were significantly less for the treated vines than for the control ones in 1985 and 1986. Pruning weights in 1986 and yield in 1987 showed no si...