Proceedings of GiESCO 2023

Vineyard nutrient management is crucial for reaching production-specific quality standards, yet timely evaluation of nutrient status remains challenging. The existing sampling protocol of collecting vine tissue (leaves and/or petioles) at bloom or veraison is time-consuming. Additionally, this sampling practice is too late for in-season fertilizer applications (e.g. N is applied well before bloom). Therefore alternative early-season protocols are necessary to predict the vine nutrient demand for the upcoming season. The main goals of this project are to 1) optimize existing tissue sampling protocols; 2) determine the amount of nutrients removed at the end of the growing season.

In modern viticulture, sustainability must be considered not only into the winery, but in the vineyard as well, being that with the most attentive interventions in order to protect the environment. In this context, the new "fungi resistant" varieties represent a valid option for reducing the negative environmental impact of agrochemicals used in viticulture, including those ones used in organic farming (given the copper accumulation into soils). Several application studies have demonstrated the enological validity of many resistant varieties, both in price and as a blend. Also, under the production point of view, the feasibility and economical sustainability of the new resistant varieties was verified. The aim of this work was to deepen the knowledge on the organoleptic characteristics of wines obtained from the Fleurtai and Soreli varieties and to compare them with the wine obtained from Tocai Friulano, the mother variety in the area destined for the production of the Lison Classico DOCG appellation. The purpose of the work is then to verify the possibility of introducing resistant varieties into the DOCG while maintaining the wine name of the appellation linked to the territory.

High quantities of chemicals are applied in the vineyard for pest and disease control. Transition towards low pesticide viticulture is a key issue to improve sustainability. Winegrowers have to gradually change their practices to engage in this transition. This work aims at analysing the pesticide use evolution during transition towards low pesticide vineyards and identify some management options mobilized by winegrowers. To understand the diversity of pathways taken towards agroecological transition, we characterized different types of pesticide use evolution.

Botrytis bunch rot occurrence is the most important limitation for the wine industry in humid environments. The effect of grapevine vegetative growth on bunch rot expression results from direct effects (cluster architecture, nitrogen status among others) and indirect ones (via microclimate). Previous studies of our group showed strong differences in bunch rot incidence between floor management treatments: cover crop (CC) vs weed-free strips under the trellis with herbicide (H). We observed that in some circumstances this reduction in bunch rot incidence occurred without major vine growth differences among treatments. The aim of the present study was to test the general hypothesis that other factors unrelated to grapevine vegetative expression could be more relevant to grapevine susceptibility to bunch rot.

The northern root-knot nematode (Meloidogyne hapla) is one of the most prevalent plant-parasitic nematodes affecting Washington State Vitis vinifera vineyards. This nematode induces small galls on roots, restricting water and nutrient uptake. In new vineyards this can impede establishment. In existing vineyards, it can exacerbate decline in chronically stressed vines. While preplant fumigation is a common strategy for M. hapla management, its efficacy is temporary and relies on broad-spectrum chemicals that undergo frequent regulatory scrutiny. The trap crop litchi tomato (Solanum sisymbriifolium) showed promise in reducing plant-parasitic nematode densities in potato. This prompted field greenhouse experiments to evaluate its potential to reduce M. hapla in V. vinifera.

The Spotted lanternfly (SLF), first detected in the U.S. in 2014, is an invasive phloem-feeding planthopper that poses a growing threat to grape and wine production in the U.S. In Pennsylvania, where it was first detected, reductions in grapevine production and fruit quality have been reported by commercial growers. Recent advances have begun to elucidate how SLF affects grapevine physiology and resource allocation, but no research has identified how SLF affects wine chemical composition and quality. Documented reductions in fruit sugar allocation due to heavy SLF phloem-feeding may have downstream effects on wine fermentation dynamics. Additionally, secondary metabolic responses stimulated by SLF may also influence berry chemical composition. The present study investigated SLF-mediated effects on wine composition through analysis of the volatile composition of wines produced from white- and red-fruited varieties of different Vitis parentage (e.g., Vitis vinifera vs. interspecific hybrids) following prolonged exposure to adult SLF phloem-feeding.

The spotted lanternfly (SLF; Lycorma delicatula) is a phloem-feeding polyphagous insect invasive to the Eastern U.S.. Since its first detection in Pennsylvania (U.S.) in 2014, large infestations and economic damage (e.g., decreased yield, vine decline, greater pesticide use) have been reported in an increasing number of vineyards, threatening the sustainability and growth of the wine industry in infested regions. Our team has been investigating the impacts of SLF phloem-feeding on physiological processes, fruit production, juice, and wine composition of different grape cultivars, and also evaluated if the SLF can transmit important grapevine pathogens. In addition, we are working closely with stakeholders to better enumerate the economic damage caused by this pest. These findings will provide relevant information to grape and wine producers to help identify action thresholds and develop a more targeted integrated pest management program.

Management of plant-parasitic nematodes is typically focused on preplant fumigation, especially in a vineyard replant scenario. While the data are clear that this practice reduces nematodes immediately after application, which is useful in annually-cropped systems, does it have staying power in perennial cropping systems? The northern root-knot nematode Meloidogyne hapla reduces the overall lifespan and productivity of vineyards, but it does so over a long time period (slow, chronic decline). In two different commercial own-rooted V. vinifera vineyards, both undergoing vineyard replanting, we explored whether preplant fumigation reduced M. hapla densities in soils immediately after application. At one of these locations, we have explored the long-term effect of fumigation by monitoring the site for seven years post fumigation.

Downy mildew is one of the most important grapevine diseases, caused by the Oomycete Plasmopara viticola. The management of the disease in organic agriculture can require up to 15 copper applications per year. However, copper accumulates in the soil, is phytotoxic and is toxic for organisms living in the soil, its use has been restricted in European Union to maximum 28 kg in 7 years. Therefore, testing of alternatives with equal effectiveness is desirable. Among those, the natural biopolymer chitosan, obtained from crab shells, proved to be effective toward downy mildew in plot experiments. The aim of our trials was to extend chitosan applications in large scale experiments in different years, cultivars and environmental conditions.

Germicidal ultraviolet-C (UV-C) light has shown promising results for suppression of several plant-pathogenic microorganims, including Erysiphe necator, which attacks grapevine. In Washington State the majority of winegrape production is in a semi-arid steppe environment, with historically low powdery mildew disease pressure, making it a promising area to deploy UV-C as a disease management tool. Trials focusing on UVC application timing and frequency will assist in developing regionally-appropriate application recommendations for eastern Washington State.