Susceptibility of grapevine pruning wounds to infection by Lasiodiplodia theobromae and Neofusicoccum parvum

The susceptibility of 1‐ and 2‐year‐old grapevine wood to botryosphaeria canker caused by Lasiodiplodia theobromae and Neofusicoccum parvum was evaluated in California in two seasons. In the 2007 dormant season, pruning‐wound susceptibility was highest when wounds were inoculated immediately after pruning in December (80% of pruning wounds were infected in Chardonnay for both fungal species and 75% and 98% in Cabernet Sauvignon for N. parvum and L. theobromae, respectively). In the 2008 dormant season, pruning‐wound susceptibility was highest in November in Chardonnay (86% and 93% for N. parvum and L. theobromae, respectively) and in December in Cabernet Sauvignon (71% and 75% for N. parvum and L. theobromae, respectively). The lowest infection rates (13–35%) were observed when vines were pruned and inoculated in March in both dormant seasons and for both cultivars. Susceptibility of pruning wounds did not differ significantly (P = 0·7612) between 1‐ and 2‐year‐old wood and consequently, pruning‐wound protection treatments should be applied to all wounds. In conclusion, grapevine pruning wounds were susceptible to infection by L. theobromae and N. parvum to varying extents throughout the dormant season in California (November–March), but, overall, susceptibility of pruning wounds was highest when inoculations were done immediately after pruning and decreased significantly as the interval between pruning and inoculation increased. Results of this study suggest that pruning grapevines in late winter (March) in California would significantly reduce the risk of infection by L. theobromae and N. parvum.     

Identification of grapevine marker genes for early,non‐destructive Eutypa lata infection diagnosis

Eutypa lata is the causal agent of eutypa dieback, a highly damaging trunk disease affecting all grape‐growing areas, with currently neither an efficient curative treatment nor an early non‐destructive diagnostic method. The present work was carried out to discover grapevine genes expressed in response to the presence of E. lata that could be useful to develop an early (before visible foliar symptoms) and non‐destructive (using grapevine leaves) diagnostic tool. Microarray analyses were carried out from (i) infected plants showing characteristic E. lata foliar and vascular symptoms and positive pathogen recovery from vascular lesions (S⁺R⁺), (ii) infected plants showing no symptoms (S^?R⁺), and (iii) symptomless plants with negative pathogen recovery (S^?R^?). Vineyard and greenhouse‐grown plants, naturally or artificially infected respectively, and uninoculated controls were characterized and leaf RNA was hybridized with 15k operon grapevine oligonucleotide microarrays. Among the grapevine genes differentially expressed between S^?R⁺ and S^?R^? plants in greenhouse and vineyard conditions, 10 were highlighted as robust candidate genes for diagnosis: seven were specifically involved in response to infection and three were associated with symptom absence. Five were confirmed to be effective diagnostic marker genes usable in a qRT‐PCR‐based test performed on RNA extracted from grapevine leaves cultivated in either greenhouse or vineyard conditions. Furthermore, their expression profiles in response to infection with E. lata or other major grapevine fungi (Erysiphe necator, Plasmopara viticola, Botrytis cinerea) could be distinguished. The usefulness of these genes to develop an early and non‐destructive method for diagnosis of E. lata infection is discussed with regard to the advantages and drawbacks of previous E. lata diagnostic studies.     

Temporal spore dispersal patterns of grapevine trunk pathogens in South Africa

Trunk disease pathogens of grapevines, viz. Phaeomoniella chlamydospora, Eutypa lata and several species in Botryosphaeriaceae, Phaeoacremonium and Phomopsis are known to infect fresh pruning wounds by means of air-borne inoculum released after rainfall or prolonged periods of high relative humidity. Recent surveys have demonstrated that most or all of these pathogens are present in climatically diverse grape growing regions of South Africa. However, the factors controlling spore dispersal of these pathogens in vineyards were largely unknown. To address this question, spore trapping was done in a Chenin Blanc vineyard in the Stellenbosch area, South Africa, for 14 weeks during the grapevine pruning period from June to mid-September of 2004 and 2005. Hourly recordings of weather data were done by a weather station in the row adjacent to the spore trap. Spores of E. lata and Phomopsis and species in Botryosphaeriaceae were trapped throughout the trapping periods of 2004 and 2005, with higher levels of trapped spores recorded in 2005. The spores of all three pathogens were trapped during or after periods of rainfall and/or high relative humidity. In neither of the 2 years were spores of Pa. chlamydospora or Phaeoacremonium spp. trapped. Results indicated that spore event incidence, as well as the amount of spores released during a spore event of above-mentioned pathogens, were governed by rainfall, relative humidity, temperature and wind speed prior to and during the spore events.     

Identification,potential inoculum sources and pathogenicity of botryosphaeriaceous species associated with grapevine dieback disease in New Zealand

This study investigated the prevalence and identity of botryosphaeriaceous dieback pathogens in necrotic grapevines tissues in New Zealand vineyards, and other woody hosts growing nearby. The presumptive identities of the isolates by conidial and cultural morphology were confirmed with ITS sequence data as Neofusicoccum australe, N. luteum, N. parvum and Diplodia seriata. They were isolated predominantly from necrotic stems of grapevine and other hosts, but also from leaves, flowers and wood debris of grapevines. Inoculation with conidia and mycelium of multiple isolates of each species onto excised and attached green shoots and trunks of five grapevine varieties, Cabernet sauvignon, Chardonnay, Pinot noir, Riesling, and Sauvignon blanc, showed that all varieties became infected to a similar extent. All species except D. seriata were pathogenic, irrespective of the host source, with N. luteum being the most and D. mutila the least pathogenic (P < 0.05). On trunks, N. parvum caused cankers and the other pathogenic species caused die-back when the inoculated vines became winter-dormant. Conidia were produced from green shoot lesions and die-back wood, which indicates potential inoculum sources for vineyard infection.     

Production of phytotoxic metabolites by five species of Botryosphaeriaceae causing decline on grapevines, with special interest in the species Neofusicoccum luteum and N. parvum

In recent years an increasing number of species of Botryosphaeriaceae have been associated with grapevine decline worldwide. Five species isolated from declining grapevines in Spain (Botryosphaeria dothidea, Diplodia seriata, Dothiorella viticola, Neofusicoccum luteum and N. parvum) were checked for toxin production in liquid cultures. Cultural conditions for all fungi were adjusted to obtain optimal production of phytotoxic culture filtrates, by growing the fungi in steady liquid cultures of Czapek–Dox broth for different time intervals. Phytotoxicity of D. seriata and N. parvum reached a maximum after 14 days while the remaining species showed the highest phytotoxicity levels after 21 days in culture. All fungi produced hydrophilic high-molecular weight compounds with phytotoxic properties. In addition, N. luteum and N. parvum produced lipophilic low-molecular weight phytotoxins, not detected consistently among the remaining species. This led to a more exhaustive study on the phytotoxicity of N. luteum and N. parvum. Culture filtrates and corresponding extracts of both species were consistently highly phytotoxic in different assays. The gas-chromatography analysis of the acetylated O-methyl glycosides of the phytotoxic exopolysaccharides produced by N. parvum showed these substances to be composed mainly of glucose, mannose and galactose. Results suggest that phytotoxic metabolites could be involved in the virulence of both species in planta.     

Development of isolate‐specific markers for Neofusicoccum parvum and N. luteum and their use to study rainwater splash dispersal in the vineyard

Unique bands were identified in single isolates of Neofusicoccum parvum and Neofusicoccum luteum using universally primed polymerase chain reaction (UP‐PCR) analysis of isolates obtained from grapevines and non‐grapevine hosts in New Zealand, Australia, South Africa and the USA. Primers were designed to amplify a 1550 bp portion of the 1573 bp marker band from N. parvum isolate B2141 and a 510 bp portion of the 524 bp marker band from N. luteum isolate G51a2. A PCR‐RFLP assay was developed to distinguish the N. parvum isolate B2141 from other N. parvum isolates, based on a polymorphism found in the marker band using the TaqI restriction endonuclease. For N. luteum isolate G51a2, the designed primers were specific at an annealing temperature of 63°C in the PCR. The sensitivity threshold of the N. parvum and N. luteum isolate‐specific markers was 50 pg and 5 pg, respectively, when used in standard PCR with purified genomic DNA. The sensitivity of the N. parvum isolate‐specific marker was increased to 0·5 pg by nested PCR. The specificity test of both isolate‐specific markers with six other Botryosphaeriaceae spp. showed that they were specific to their respective species and isolates. Both markers were able to detect the conidia of N. parvum and N. luteum marker isolates in rainwater samples collected at different distances from an inoculation point in the vineyard. The results showed that rain splash could disperse the conidia of both of these species up to 2 m from the inoculum point in a single rainfall event.     

Trichoderma harzianum produces nonanoic acid, an inhibitor of spore germination and mycelial growth of two cacao pathogens

An isolate of Trichoderma harzianum Rifai from an infected cacao pod produces and secretes nonanoic (pelargonic) acid into a liquid culture medium. Nonanoic acid (NA) was very inhibitory to spore germination and mycelial growth of two cacao pathogens, Crinipellis perniciosa Stahel and Moniliophthora roreri Cif. H.C. Evans. It was highly active causing 75% inhibition of spore germination in an in vitro assay at a rate as low as 0.09 μM for M. roreri and 0.92 μM for C. perniciosa. Mycelial growth was comparatively less sensitive to inhibition, but still there was a 75% reduction in growth with 0.62 μM in M. roreri and 151 μM NA in C. perniciosa. In contrast, NA did not affect Trichoderma mycelial growth or spore germination at concentrations that were inhibitory to the pathogens. 6-pentyl-α-pyrone was also produced and secreted into the medium by T. harzianum, however; it was not antagonistic to the cacao pathogens. Although a number of metabolites produced by Trichoderma spp. have been identified in the past, this is the first report of NA production and secretion by any Trichoderma. The results suggest that NA may play a role in the successful use of some Trichoderma spp. isolates in the biocontrol of fungal diseases of plants.     

Characterization of Cytospora isolates from wood cankers of declining grapevine in North America,with the descriptions of two new Cytospora species

Cytospora species are ubiquitous pathogens of numerous woody plants, causing dieback and wood cankers in agronomic crops, timber trees and wildland trees (e.g. Prunus, Eucalyptus and Salix, respectively). Cytospora chrysosperma, C. cincta and C. leucostoma have been reported from grapevines in Iran showing symptoms of one or more recognized trunk diseases (esca, botryosphaeria‐, eutypa‐ and phomopsis diebacks); however, only C. chrysosperma was shown to be pathogenic to grapevine. To understand the potential role of Cytospora species in the grapevine trunk‐disease complex, 21 Cytospora isolates were examined that were recovered from dieback and wood cankers of Vitis vinifera and Vitis interspecific hybrids in seven northeastern U.S. states and two Canadian provinces. Phylogenetic analyses of ITS and translation elongation factor 1‐α identified two novel species: Cytospora vinacea sp. nov. and Cytospora viticola sp. nov. Differences in culture morphology and conidial dimensions also distinguished the species. When inoculated to the woody stems of potted V. vinifera ‘Thompson Seedless’ in the greenhouse, both species were pathogenic, based on development of wood lesions and fulfilment of Koch's postulates. Cytospora viticola was the most virulent based on lesion length at 12 months post‐inoculation. As cytospora canker shares some of the same general dieback‐type symptoms as botryosphaeria‐, eutypa‐ and phomopsis diebacks, it may be considered part of the grapevine trunk‐disease complex in eastern North America.     

The influence of formulation on Trichoderma biological activity and frosty pod rot management in Theobroma cacao

Frosty pod rot (FPR), caused by Moniliophthora roreri, is responsible for significant losses in Theobroma cacao. Due to limited options for FPR management, biological control methods using Trichoderma are being studied. Combinations of three formulations and two Trichoderma isolates were studied between May 2009 and April 2011. The formulations were 0·3 mL L^?1 of the surfactant BreakThru 100SL (BT), a mixture of 1% w/v Sure‐Jell (source of pectin) and 1% w/v potato dextrose broth (PDB) (PP), and an invert oil emulsion of 50% v/v corn oil/2·5% w/v lecithin/0·5% w/v PDB (COP). Water and fungicide, copper oxychloride, were included as controls. Humidity chamber studies indicated that Trichoderma conidia germinated in all formulations if free water was maintained, while only the COP formulation supported germination under drying conditions. In the field, Trichoderma ovalisporum DIS‐70a and Trichoderma harzianum DIS‐219f were applied monthly in each of the three formulations at a rate of 180 mL per tree, 2·46 × 10⁷ conidia per mL. The COP/DIS‐70a formulation provided the largest yield increase compared to all other treatments, including the fungicide control. Averaged over the 2 years, the COP formulation increased yield to 30·7% healthy pods compared to 9·7% healthy pods in the water control. Although the formulation/isolate combinations did not consistently increase endophytic colonization, the PP/DIS‐219f, COP/DIS‐219f and COP/DIS‐70a combinations increased total endophytic/epiphytic colonization by Trichoderma. The invert corn oil formulation of DIS‐70a significantly enhanced yield of healthy cacao pods over 2 years providing a promising model for optimizing Trichoderma‐based biocontrol strategies.     

Aetiology of branch dieback,panicle and shoot blight of pistachio associated with fungal trunk pathogens in southern Spain

Pistachio represents an emerging nut crop across the Mediterranean basin. In Spain, pistachio has been traditionally cultivated in marginal-dry areas with unfavourable climatic conditions for plant diseases. Consequently, little attention has been given to research on pistachio diseases until recently. Symptoms of branch dieback and cankers, and shoot and panicle blight have been recently observed in commercial pistachio orchards across southern Spain. In this study, 10 commercial pistachio orchards showing disease symptoms were surveyed between 2017 and 2018. Botryosphaeriaceae fungi were consistently isolated from affected shoots, among other fungal families with minor relevance. Representative isolates of each family were characterized based on colony and conidial morphology, optimum growth temperature, and the comparison of DNA sequence data (ITS, LSU, EF, TUB2, and ACT genomic regions). Detached and attached shoots, and attached panicles of pistachio cv. Kerman were inoculated with mycelial plugs or conidial suspensions to demonstrate the pathogenicity of the selected isolates. Botryosphaeria dothidea, Lasiodiplodia pseudotheobromae, Neofusicoccum mediterraneum, N. parvum, Diaporthe neotheicola, Diaporthe sp., Eutypa lata, Eutypa sp., Cytospora sp., and Phaeoacremonium minimum were identified. P. minimum had the highest optimum growth temperature (29.6 °C) and Cytospora sp. the lowest (21–22 °C). Botryosphaeriaceae isolates showed the largest lesions on inoculated shoots, with L. pseudotheobromae being the most aggressive, followed by Neofusicoccum species. Panicles inoculated with N. mediterraneum showed blight symptoms and canker formation 6 weeks after inoculation, without significant differences in aggressiveness between isolates. This work reports relevant information about this emerging disease in the novel Spanish pistachio-growing areas.     

Detection of Botryosphaeriaceae species within grapevine woody tissues by nested PCR, with particular emphasis on the Neofusicoccum parvum/N. ribis complex

Several species of Botryosphaeriaceae and Phaeomoniella chlamydospora are common agents of grapevine decline worldwide. Currently, the use of culture independent PCR based techniques for detection of Botryosphaeriaceae within grapevine tissues has been limited to Botryosphaeria dothidea. In the present study, two Botryosphaeriaceae specific nested PCR assays were developed. One with a narrow target range, to detect Neofusicoccum parvum and the closely related species complex (Neofusicoccum parvum/N. ribis sensu Pavlic et al. Molecular Phylogenetics and Evolution 51:259–268, 2009) and another, with a wider range, to detect all 17 species of Botryosphaeriaceae which have been reported as potential wood pathogens of grapevine. The effectiveness of these assays was validated in vivo on naturally infected wood samples collected from standing vines and dormant grafted rooted cuttings commercialized in Italy by different nurseries in different years. All samples were also screened by means of a previously published nested PCR assay specific for Phaeomoniella chlamydospora. It was found that: 1) propagation material may play an important role as source of primary inoculum, not only of Phaeomoniella chlamydospora, as previously reported, but also for members of the Botryosphaeriaceae, among which Neofusicoccum parvum, Botryosphaeria dothidea and Diplodia seriata are the most common, and 2) multiple infections by different species belonging to Botryosphaeriaceae and/or Phaeomoniella chlamydospora occur frequently both in standing vines and propagation material. This last finding supports the hypothesis that at least some of the non-specific symptoms of grapevine decline may be due to the presence of different pathogens within host tissues.     

Biological and integrated control of grey mould of grapevine: results in Italy1

Three experimental trials were carried out in Northern Italy during 1985 and 1986 in order to control grey mould of grapevine (Botrytis cinerea) by using isolates of Trichoderma spp. resistant to several fungicides commonly sprayed against grapevine pathogens, alone or in alternation with benzimidazoles or dicarboximides, in vineyards where fungicide-resistant strains of B. cinerea are frequent. The antagonists alone partially controlled the pathogen on cv. Moscato ?Asti. In one case, the integration of chemical and biological control measures showed slightly better results than for the fungicide alone (for benomyl but not for vinclozolin), but further trials are needed to investigate the full potential for using fungicide-resistant Trichoderma in alternation with fungicides. Trichoderma spp. performed very poorly on cv. Barbera.     

High genetic and virulence diversity detected in Neofusicoccum luteum and N. australe populations in New Zealand vineyards

Genotypic and virulence diversity of Neofusicoccum luteum and N. australe isolates recovered from grapevines displaying symptoms of dieback and decline in New Zealand were investigated. The universally primed PCR (UP‐PCR) method was used to investigate the genetic diversity of 40 isolates of N. luteum and 33 isolates of N. australe. Five UP‐PCR primers produced a total of 51 loci from N. luteum and 57 from N. australe with a greater number of polymorphic loci produced in N. australe (86%) compared with N. luteum (69%). Analysis of UP‐PCR data showed both species found in New Zealand vineyards were genetically diverse at both the inter‐ and intra‐vineyard levels with only a single pair of clonal isolates in N. luteum. Cluster analysis of UP‐PCR data produced four genetic groups in N. luteum and 10 in N. australe (P < 0.05). For both species, there was no relationship between the genetic groups and the origin of isolates. The mean genetic diversity (H) of N. luteum was less than for N. australe, being 0.1791 and 0.2417, respectively. Pathogenicity assays of both species using isolates from either the same or different genetic groups inoculated onto either green shoots or grapevine trunks, showed virulence diversity within the population; however, no correlation was identified between genetic groups and virulence.     

Resistance against Botrytis cinerea in smooth leaf pruning wounds of tomato does not depend on major disease signalling pathways

In high‐tech, heated tomato glasshouses, stem infections caused by Botrytis cinerea usually end up girdling the stem, resulting in plant death and consequently high economic losses. Such infections originate primarily from wounds created during leaf pruning, a common cultural practice in which it is intended to remove leaves completely, resulting in smooth stem wounds. However, hasty leaf pruning often results in numerous petiole stubs accidentally left behind. In this study analysis of disease incidences clearly proved that pruning leaves flush to the stem resulted in absolute resistance of the stem wounds, whereas petiole stubs displayed a high level of susceptibility to B. cinerea. Postponing inoculation of wounds after pruning indicated that development of nearly complete resistance occurs within 48 h after deleafing. Monitoring of the wound wetness period showed that drying of the wound surface is not the cause of the decreased susceptibility, contrary to what was commonly believed. Tomato mutants deficient in disease signalling showed altered phenotypes for susceptibility to B. cinerea, indicating that defences against this pathogen in petiole stubs depend on ethylene signalling. Additionally, the decreased susceptibility of mutants deficient in the biosynthesis of jasmonates and abscisic acid suggest an antagonistic effect of these signal molecules. On the other hand, resistance of smooth stem wounds could not be altered by disruption of salicylic acid, ethylene, jasmonate or abscisic acid signalling. This indicates that this remarkable absolute resistance to B. cinerea does not depend on the major disease signalling pathways.     

Detection of viridiofungin A and other antifungal metabolites excreted by <Emphasis Type="Italic">Trichoderma harzianum</Emphasis> active against different plant pathogens

Antibiosis is assumed to be an essential mechanism exerted by potential biocontrol agents (BCAs) of Trichoderma spp. Therefore, in the present study, we report for the first time on the elucidation and production of viridiofungin A (VFA) from T. harzianum isolate T23 cultures and investigate the antifungal potential of VFA and some other secondary metabolites purified from T. harzianum cultures against Fusarium moniliforme. The bioautography assay revealed that T. harzianum isolates T16 and T23 excreted several secondary metabolites with antifungal activity. Following isolation and purification of the antifungal zones, three fractions (F223, F323 and F423) from extracts of isolate T23 and two fractions (F416 and F516) from extracts of isolate T16 exhibited pronounced fungitoxic activity in the bioautography and antibiotic disk assays against Cladosporium spp. and F. moniliforme, respectively. The structure of the antifungal metabolite in fraction F323 was identified as viridiofungin A (VFA), the first report of production of VFA by isolate T23 of T. harzianum. Following cultivation of isolate T23 in PDB medium for 9 days, 94.6 mg l⁻¹ of VFA were determined. VFA and fraction F516 retarded the mycelial growth of F. moniliforme in the non-volatile phase assay by >90% for each 250 μg ml⁻¹ 7 days post-inoculation (dpi). While VFA and fraction F416 showed both volatile and non-volatile effects, fraction F516 seemed to exhibit mainly non-volatile activity. Microscopic examination revealed that hyphae of F. moniliforme grown on VFA-amended medium were less branched and appeared thicker than untreated hyphae. Furthermore, in the presence of VFA, formation of chlamydospores by F. moniliforme was increased. Finally, the antifungal spectrum of VFA towards various important plant pathogens was evaluated. Germination of propagules of a variety of fungal pathogens in vitro was differentially inhibited by VFA. While in the presence of 100 μg ml⁻¹ VFA conidial germination of V. dahliae was completely inhibited, a slightly higher concentration (150 μg ml⁻¹) of the inhibitor was required to suppress germination of Phytophthora infestans sporangia or sclerotia of Sclerotinia sclerotiorum. Contrary to several reports in the literature, VFA proved to be fungistatic rather than fungicidal. However, neither VFA nor the other Trichoderma metabolites, such as 6PAP, F416 and F516, exhibited any antibacterial activity against Gram-positive and Gram-negative bacteria.     

Limited asymptomatic colonization of apple tree shoots by Neonectria ditissima following infection of leaf scars and pruning wounds

European apple canker, caused by Neonectria ditissima, is an important disease of apple (Malus domestica). The fungus may reside in the tree without causing symptoms for up to a few years, thus making canker control difficult. Asymptomatic infections established in the nursery can result in severe canker outbreaks in newly established apple orchards. It has been suggested that N. ditissima might colonize the tree beyond the infection point during the asymptomatic stage. We investigated whether N. ditissima can colonize the internal tissues of apple shoots, both prior to and after visual symptoms. Apple trees were artificially inoculated via pruning wounds and leaf scars; then the pathogen was tracked at the inoculation point and beyond with isolation or real-time quantitative PCR (qPCR). Before visual symptoms, N. ditissima could be detected in the infected pruning cut or leaf scar, but not at a distance of 10–15 mm from the entry point, or greater. Conversely, after symptom expression, the pathogen could be detected in the symptomless tissue at 10–15 mm from a canker lesion. This study demonstrated that the asymptomatic infection by N. ditissima can be detected using qPCR and that the pathogen does not grow systemically much beyond the initial entry point inside the plant before visual canker symptoms appear.     

Pre‐infection processes of Botryosphaeriaceae spp.: adhesion of conidia to different substrata

Species of Botryosphaeriaceae are important wound pathogens of grapevines as causal agents of botryosphaeria dieback, but the behaviour of their conidia pre‐infection is unknown and may be important for disease development. Adhesion properties of conidia were investigated for Botryosphaeria dothidea, Neofusicoccum luteum and N. parvum on substrata with different affinities for water. Greatest adhesion on any surface was reached after 5 min for isolates N. luteum MM558, B. dothidea 007 and N. parvum G652 (53·1, 54·0 and 50·6%, respectively) and for N. luteum isolate CC445 after 20 min (61·4%). As conidia adhered well to all artificial substrata, it appeared as if the attachment process was nonspecific. Overall, surface wettability did not play a major role in the adhesion of conidia. Spore surface proteins appeared to play a role in the adhesion process because treatment of conidia of N. luteum MM558 with a protease completely prevented adhesion. Histochemical labelling of conidia and germlings with Coomassie brilliant blue (specific for proteins) was positive for all isolates, with a blue ‘halo’ often seen surrounding conidia or near the germ tube emergence point after incubation times conducive to germination. Alcian blue also stained material surrounding conidia after longer incubation times, which indicated that mucopolysaccharide and protein production may be involved in a second phase of adhesion.     

Eradication of black rot (Guignardia bidwellii) from grapevines by drastic pruning

A drastic pruning strategy was developed to eradicate the fungal disease black rot (Guignardia bidwellii), which is exotic in Australia, from grapevines, while minimizing the economic cost of returning an affected vineyard to its previous quality and production levels. The protocol involved cutting off vines at the top of the trunk, removing debris from the ground beneath and between vines, mulching the vineyard floor, removing low watershoots during vine regrowth and applying a targeted fungicide programme. The protocol was initially evaluated and consequently modified in Australia using an endemic grapevine disease, black spot or anthracnose (Elsinoe ampelina), as an analogous model system. Then, it was validated in a black‐rot‐infested vineyard in New York, USA. Following two seasons of disease‐conducive weather conditions, no black rot was detected on treated vines, whereas leaf and fruit infections developed on the untreated control vines. These results confirmed the efficacy of the protocol for eradicating black rot from vineyards while allowing vines to return quickly to previous yield and quality levels without replanting. The protocol may have applicability to disease eradication protocols for other perennial crops as well. Evidence is also presented on the efficacy and potential pitfalls of burning infected grapevine material to eradicate E. ampelina.