Understanding the control strategies effective against the esca leaf stripe symptom: the edge hypothesis

A peculiar symptom that may develop in grapevines affected by wood pathogens involved in the esca complex of diseases is the leaf stripe symptom, which also gives the name to the Grapevine Leaf Stripe Disease. Multiple studies have revealed strong links between fungal presence, wood symptomatology and expression of the leaf stripe symptom. However, numerous other factors have been shown to play roles in symptom onset, incidence, severity and yearly fluctuation of this disease. While the factors triggering the leaf stripe symptom are still under investigation, three control strategies have been proven effective for substantially reducing its expression, namely trunk surgery, and applications of sodium arsenite or a fertilizer mixture. These control strategies are examined here, including their (putative or confirmed) modes of action, and how they may influence the leaf stripe symptom development. In this article, we also propose the ‘edge’ hypothesis to tentatively explain symptoms onset, keeping in consideration past knowledge and recent advances in the understanding of the esca leaf stripe symptom. Ultimately, it is our intention to offer food-for-thought and and stimulate and stimulate debate within the phytopathological community

Italian Zeolitites in the Control of Grey Mould and Sour Rot and Their Effect on Leaf Reflectance, Grape and Wine

Abstract: The activity of two zeolitites, differing in the presence of copper and their particle size, was assessed in a Trebbiano d’Abruzzo white berry cultivar, towards grapevine grey mould and sour rot, a serious problem in almost all grapevine-growing areas. In 2018 and 2019, zeolitites were applied before forecast of rainfalls, which likely induce infection. In 2019, further applications were carried out 10 or 2 days before harvest, regardless of the rainfall, in order to verify the effect of the zeolitite residue on leaf reflectance and composition of grapes and wines. Both zeolitites significantly reduced the infections. Only the vines treated 2 days before harvest, especially with copper zeolitite, showed a decrease in leaf reflectance. However, no differences in the yield composition related to the time of zeolitite application, as well as a decrease of yield quality, were ever recorded. Furthermore, analysis of samples collected from vines treated with zeolitites showed increases in grape soluble solids and in wine alcohol content. Our results suggest the use of zeolitites against grapevine rots as a possible effective alternative to the application of synthetic fungicides in the development of environmentally friendly control strategies

Preliminary Evaluation of Variations in Composition Induced by Esca on cv. Trebbiano d'Abruzzo Grapes and Wines

The present study examined the effect on quality caused by esca in both grape clusters and wines. In the last year (2000) of an eight-year survey of esca foliar symptoms, the vines of two cv. Trebbiano d’Abruzzo vineyards fell at the moment of grape clusters sampling, into 3 groups: 1. vines with esca symptoms; 2. vines that happened to be asymptomatic but that were known to be diseased because they had show leaf symptoms in at least one other survey year and 3. healthy vines. In a third vineyard, in the same growing area, grape clusters were sampled from vines with trunk renewal that had been restored and from unrenewed vines that had never shown esca leaf symptoms and were consequently presumed to be healthy. Preliminary results on grape clusters in the first two vineyards showed differences in composition between symptomatic vines on the one hand, and asymptomatic/diseased vines and healthy vines on the other, with symptomatic vines having lower levels of reducing sugars and a higher nitrogen concentration. As a result the alcohol content of wines from symptomatic vines was about 1% v:v lower than that of wines from the other two groups of vines. Grape clusters and wines from diseased/asymptomatic vines and healthy vines did not differ in the compositional parameters used in the test except for total polyphenols which gave contrasting data among the first two vineyards. In grape clusters and wines from the third vineyard the preliminary results likewise revealed no difference between vines with trunk renewal and unrenewed healthy vines. This finding would seem to corroborate the practice of trunk renewal as a means of restoring both vines and the quality of grape clusters. Research is continuing to evaluate the reliability of these results

Control of Grapevine Downy Mildew by an Italian Copper Chabasite-Rich Zeolitite

Abstract: The progressive reduction in the quantities of copper regulated by the European Union is focusing the research on new formulations with a reduced copper content but equally effective. In this regard, the activity of an Italian copper chabasite-rich zeolitite, which proved to be effective against grapevine grey mold and sour rot, was assessed against downy mildew. A two-year study was carried out in the Abruzzo region, Italy, in a cv. Montepulciano vineyard. The applications of the copper zeolitite showed the same good results obtained by a standard integrated/conventional strategy based on contact and systemic fungicides. At harvest, in both trial years, the plants with infected bunches in the untreated control ranged from 86.25% to 100%, compared to 15–30% of the treated plants. Furthermore, infected bunches and berries of the untreated control vines were 70–100% while treated ones never exceeded 2.32%. Furthermore, an increase in the polyphenol content and color intensity in wines made from vines treated with copper zeolitite was confirmed and appeared to be particularly evident in hot and dry seasons. The activity of copper zeolitite towards downy mildew, the potential use against grey mold and sour rot and the protection of grapes from high temperatures indicate that this product is a promising tool for a viticulture environmentally friendly control strategy

Rainfall and temperature influence expression of foliar symptoms of grapevine leaf stripe disease (esca complex) in vineyards

Two vineyards in the Abruzzo Region, central Italy, affected by grapevine leaf stripe disease (GLSD), were monitored for incidence and severity of foliar symptoms of the disease for 21 consecutive years (1994 to 2014). Each year, rainfall and temperature were recorded. Correlations between symptom incidence or severity and rainfall or temperature of different periods of the year or single months were assessed. July rainfall and temperature were highly correlated with incidence and severity of leaf symptoms. The vineyards were characterized by high longevity, vigour and yields, and a particular dynamic of GLSD. In the period following 2005, the year of peak vine mortality, there was a decrease of the expression of foliar symptoms, which was not correlated with both of the climate parameters. Greater mortality occurred for vines showing severe symptoms at the first appearance of GLSD than for vines with low severity

The Contro of Esca : Status and Perspectives

The development of an effective control strategy for esca greatly depends on major progress in understanding the disease biology and epidemiology. Experimental trials were carried out in vineyards and single infected vines in order to evaluate the effectiveness of different fungicides, application methods and cultural practices in controlling esca: experiences with sodium arsenite, dinitro-orthocresol, fosetyl Al, triazoles and first attempts with Trichoderma are discussed. Ongoing trials show promising results with fosetyl Al activity against Phaeoacremonium spp. under laboratory and greenhouse conditions, with the prospect of a favourable effect on esca control. Research is now being focused on the potential of a control strategy to prevent or reduce the establishment and development of the disease. The management of esca should be based on the age of the plant, the stage of the infection as well as the degree of spread of the disease

Grapevine leaf stripe disease symptoms (esca complex) are reduced by a nutrients and seaweed mixture

Grapevine leaf stripe disease (GLSD) seriously reduces the quality and quantity of grape production, and results in a shorter lifespan of vineyards. Recent research has shown that foliar applications of nutrients influence the development of GLSD foliar symptoms. Based on this knowledge the effect of foliar applications of a mixture of calcium chloride, magnesium nitrate and Fucales seaweed extract on the development of leaf symptoms was evaluated over a 3-year period from 2010 to 2012. Nine foliar applications of the full mixture and its individual mineral components, also in different combinations, were tested in three different vineyards, one of cv. Trebbiano d’Abruzzo and two of cv. Montepulciano d’Abruzzo in the Teramo province (Abruzzo, Italy). Treatments were applied every 10 days from the beginning of vegetative growth to pre-bunch closure. The final results were similar in all the three vineyards and in the three years leading to a significant reduction of symptom development in the vines treated with the full mixture, while lower effects were obtained by applying partial combinations or single components. Both quantity and quality of grapes from the treated vines increased, while no phytotoxic or other unwanted effects on grape growth were detected. Vines treated with the full mixture showed an increase in trans-resveratrol and flavonoids content, and a higher accumulation of calcium oxalate in crystal druses in the leaf mesophyll. These data can be a useful base to set up a control strategy against GLSD and give some input for better understanding the mechanisms involved in foliar symptom expression in GLSD

Mixture of calcium, magnesium and seaweed affects leaf phytoalexin contents and grape ripening on vines with grapevine leaf stripe disease

Grapevine leaf stripe disease (GLSD) is a tracheomycosis caused by Phaeomoniella chlamydospora and Phaeoacremonium minimum. Impacts on yields of grapes were correlated with the incidence and severity of GLSD symptoms on vine canopies. In 2012 and 2013, vines in two vineyards were treated with nine applications of a mixture of leaf fertilizers containing calcium, magnesium and seaweed extracts. At different growth stages, leaves were sampled from treated and control plots of healthy, GLSD-asymptomatic, or GLSD-symptomatic vines and contents were measured of the phytoalexins trans-resveratrol, trans-ε-viniferin, trans-δ-viniferin and trans-pterostilbene. Grape ripening was also monitored from veraison to harvest during both vintages. The treatments caused significant reductions in canopy symptom expression. Increased phytoalexin contents were measured from ‘fruit set’ to ‘berries developing colour’ stages. Trans-resveratrol peak was recorded in asymptomatic diseased vines at the ‘berries pea-sized’ stage, and trans-ε-viniferin and trans-δ-viniferin increased at the ‘berries beginning to touch’ stage, compared to the contents recorded in untreated asymptomatic vines. From ‘berries developing colour’ to harvest, all treated vines had lower amounts of phytoalexins than the control ones. At harvest, treated healthy and symptomatic vines produced berries with similar amounts of total sugars compared to untreated vines. Treated asymptomatic vines produced berries with greater amounts of total sugars compared to the untreated vines. These results indicate that increased phytoalexin content recorded from ‘fruit set’ to ‘berries beginning to touch’ in asymptomatic vines treated with the mineral/seaweed mixture may reduce symptoms of GLSD

Incidence of symptoms and fungal pathogens associated with grapevine trunk diseases in Czech vineyards: first example from a north-eastern European grape-growing region

Grapevine trunk diseases (GTD) are one of the most important constraints for grapevine and wine production worldwide. Most of the published studies on these diseases in Europe relate to the major vine growing regions mainly located in southern Europe. This is the first study of GTD incidence and associated fungal pathogens in Czech vineyards, as an example of the north-eastern European grape-growing region. Annual incidence of GTD symptoms in vineyards of cvs. ‘Chardonnay’ and ‘Cabernet Sauvignon’ in three Czech locations was surveyed. On average, 3.7% of the ‘Chardonnay’ plants showed GTD symptoms and 0.7% suddenly collapsed each year. Within the ‘Cabernet Sauvignon’ vineyards, 10.1% of the plants showed GTD symptoms and 2.5% suddenly collapsed. Several fungal pathogens were associated with the suddenly collapsed grapevines, and the most frequent was Phaeomoniella chlamydospora (77% of analyzed grapevines), followed by Eutypa lata (62%), Diaporthe ampelina (31%), Botryosphaeria dothidea (15%) and Fomitiporia mediterranea (15%)

Patterns of phytoalexins in the grapevine leaf stripe disease (esca complex)/grapevine pathosystem

Vineyards containing vines affected with grapevine leaf stripe disease (GLSD), one of the diseases of the esca complex, suffer losses in grape yield and quality every growing season. To examine the relation between GLSD foliar symptoms and levels of phytoalexins in grapevine, phytoalexin levels were monitored in the leaves of symptomatic, asymptomatic/diseased, and healthy grapevine leaves, at various growth stages, in two vineyards in Italy, over four growing seasons. At the same time, the leaf symptoms of the vines at some of those growth stages were recorded in each vineyard and in each growing season. The compounds extracted and identified were: trans-resveratrol, trans-pterostilbene, trans-ε-viniferin and trans-δ-viniferin. The most common phytoalexin found was resveratrol. Amounts of all the phytoalexins were generally greater in symptomatic leaves than in asymptomatic/diseased or healthy leaves. In symptomatic leaves, resveratrol levels were greatest at pre-bunch closure, and peaks in pterostilbene occurred at the same time. Leaves of each category (symptomatic, asymptomatic/diseased, healthy) had lower amounts of these compounds at veraison and generally higher amounts at the stages of harvesting and/or the softening of berries. It seems therefore that the formation and pattern over time of the phytoalexins was linked to the growth stage of the vines. Leaf symptoms never occurred before pre-bunch closure, but became much more common from veraison to harvest. This study provides evidence of a relationship between the levels of phytoalexins, grapevine growth stage, and the seasonal pattern of development of GLSD symptoms