Stefano Di Marco

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.

Application of "Trichoderma" to Prevent "Phaeomoniella chlamydospora" Infections in Organic Nurseries.

Summary. In order to prevent or reduce infection in grapevine nurseries, greenhouse and nursery trials were carried out to evaluate the effects of Trichoderma harzianum (Rootshield ® ) on the morpho-physiological characteristics of grapevine and on Phaeomoniella chlamydospora artificially inoculated on potted cuttings. The long-distance activity of Trichoderma against Botrytis cinerea was also examined. The study was performed in a commercial nursery where plants were grown organically. Results greatly depended on the vine-growth stage at which Trichoderma was applied. Treatment at rooting was the most effective, whilst callusing-box application or treatments at both rooting and callusing gave inconsistent but generally negative results. Treatment at rooting further improved the quantitative and qualitative characteristics of the root system, and increased the percentage of certifiable vines produced. Moreover, Trichoderma application also reduced the necrotic area caused by B. cinerea inoculated on the leaves collected from Trichoderma-treated plants and the extent of necrosis of P. chlamydospora-inoculated cuttings. This reduction in necrosis was significantly higher 15 months after inoculation. On the other hand, Trichoderma increased vine mortality at the end of the growing season compared with untreated plants. On the whole, only when it was applied at rooting did Trichoderma produce positive effects on the morpho-phisiological characteristics of grapevine and increased its tolerance to stress–related diseases, such as forms of esca found in the nursery.

Some Observations on the Relationship of Manifest and Hidden Esca to Rainfall

Summary. This paper reports observations on the relationship between the yearly incidence of manifest esca (i.e. diseased plants which show foliar symptoms), hidden esca (that which remains asymptomatic throughout a growing season) and rainfall. Data from three vineyards (two in Tuscany and one in Emilia-Romagna, Italy) showed that rainfall in May–July or only in July was inversely related with hidden esca. For two vineyards, TB in Emilia-Romagna and CAR-3 in Tuscany, the spatial pattern of diseased vines in the first year of appearance of the foliar esca symptoms was also determined. The maps of the vines in these vineyards indicated that diseased plants mostly occurred alone. This suggests that the disease had its origin in infected rooted cuttings or was triggered by inoculum aerially dispersed from distant sources and/or occurring, at least in hypothesis, in the soil.

Foliar Symptom Expression of Wood Decay in Actinidia deliciosa in Relation to Environmental Factors

Kiwifruit vines (Actinidia deliciosa var. deliciosa) have recently been affected by a new form of decay caused by several fungi that produce different types of wood deterioration in the trunk and cordons. Surveys were conducted over a period of 5 years to investigate epidemiological aspects of the disease in a typical Italian growing area (Emilia-Romagna), where kiwifruit is widely cultivated and where the disease was noted for the first time. The disease was widespread over the kiwifruit growing area surveyed, and its incidence increased over the course of the survey. No relationship was found between vineyard soil characteristics or management methods and the annual incidence of symptomatic vines. Foliar symptoms did not consistently express every season even on obviously infected vines. The time of appearance and the development of the disease were correlated with plant phenology and temperature. In particular, from June to August, temperature seemed to affect the annual incidence of the disease in terms of both symptomatic shoots and symptomatic vines. The aspects in common between the decay of kiwifruit and esca of grapevine could be hypothesized and are discussed.

An environmentally sustainable approach for the management of Phaeoacremonium minimum, the main agent of wood diseases in Actinidia deliciosa

Among the fungi associated with the kiwi wood diseases, the vascular pathogen Phaeoacremonium minimum can infect plants already at nursery stage, without any external symptoms. At the moment, there are not effective control strategies. The effect of soil treatments applicable in organic agriculture was evaluated in two-years experiments on potted kiwi plants artificially inoculated with P. minimum. The soil treatments were based on commercial formulations of iron chelate, silicon, neem paste, Trichoderma afroharzianum strain T22, and cover cropping with selected perennial Poaceae. Cover cropping and iron chelate treatments enhanced the iron availability for the plants and significantly reduced wood necrosis caused by the pathogen. Both treatments also produced an increase of hairy root proliferation, so the plants were able to better cope with stress conditions. Laboratory assays showed the role of iron on the pathogen growth and its pathogenesis enzyme activities.

Functionalization of a nanostructured hydroxyapatite with Cu(II) compounds as a pesticide: in situ transmission electron microscopy and environmental scanning electron microscopy observations of treated Vitis vinifera L. leaves: HA functionalized with Cu(II) compounds on grapevine leaves

BACKGROUND The present study evaluated a biocompatible material for plant protection with the aim of reducing the amount of active substance applied. We used a synthetic hydroxyapatite (HA) that has been studied extensively as a consequence of its bioactivity and biocompatibility. An aggregation between HA nanoparticles and four Cu(II) compounds applied to Vitis vinifera L. leaves as a pesticide was studied. Formulations were characterized by X-ray diffraction (XRD), dynamic light scattering (DLS) and electron microscopy and applied in planta to verify particle aggregation and efficiency in controlling the pathogen Plasmopara viticola. RESULTS The XRD patterns showed different crystalline phases dependig on the Cu(II) compound formulated with HA particles, DLS showed that nanostructured particles are stable as aggregates out of the nanometer range and, in all formulations, transmission electron microscopy (TEM) and environmental scanning electron microscopy (ESEM) microscopy showed large aggregates which were partially nanostructured and were recognized as stable in their micrometric dimensions. Such particles did not show phytotoxic effects after their application in planta. CONCLUSION A formulation based on HA and a soluble Cu(II) compound showed promising results in the control of the fungal pathogen, confirming the potential role of HA as an innovative delivery system of Cu(II) ions. The present work indicates the possibility of improving the biological activity of a bioactive substance by modifying its structure through an achievable formulation with a biocompatible material.

New approaches for the reduction of foliar symptom expression in the esca complex of grapevine: nutrients and defense induction

frEsca is currently the most concerning grapevine disease in Europe. This trunk disease affects the longevity of vineyards and is characterized by the development of large inner necroses in the grapevine wood before partial or complete dieback of affected vines. In France, the overall average impact of trunk diseases is now estimated at about 13% of vines impaired in their production potential. This impact was only about 5% in 2003. Esca disease largely contributed to this overall impact. Different biotic and abiotic factors may explain this progression. Examination of plot by plot data has shown very high variability of damage between plots of the same cultivars, with the same age in similar environments. In some cases, the range of variability of damage strongly suggested the influence of cultural factors. For example, Cabernet Sauvignon in the Bordeaux area in 2007, with a vineyard planted in 1982 showing overall impact of 3% of esca-affected vines while another vineyard planted in 1990 exhibited an impact of 80%). Among them, two factors were identified as putative key influences: the training system and the quality of pruning. A survey was undertaken from 2007 by UMR SAVE Bordeaux to attempt to identify comparable plot situations forming pairs with the same variety, the same age and similar soil and climatic environments but varying according training decisions. The study was based on observations in Aquitaine in late summer. Ratings were applied for all esca symptoms, on leaves and on the trunks. Several selected examples showed that training systems leading to long arms were generally less affected than the forms with very short arms or without arms. The quality of the pruning system may also play a major role. Higher vine densities/ha, decided by grower choice or by the rules imposed by the appellations (and not accompanied by a minimum distance between vines), led growers to modify their training system over time, towards simplification of the vine trunk structure that was too great. The study also indicated that the foliar symptoms of esca are relevant clues to reveal the presence of the disease but are not always reliable indicators of impact. Real prospects in terms of reduced damage seem possible only by effective training decisions.This research is presently integrated in a national project entitled “Assessment of the impact of cultural practices or environmental factors for the control of grapevine trunk diseases”. This project is financed via grants from CasDAR (Account of Specific Affectation for Agricultural and Rural Development) and CNIV (National Committee of the Interprofessions of Wines with Label of origin and with Geographical Indication).