Pruning Wounds Research Articles

Temporal susceptibility of grapevine pruning wounds to trunk pathogen infection in South African grapevines.

Grapevine trunk diseases, caused by a range of phytopathogenic fungi, represent a serious impediment to wine and table grape production wherever these crops are cultivated. Previous studies have shown that the distribution of these pathogens is influenced by climate and that they are associated with a variety of internal wood decay symptoms. Little was known, however, about the influence of climate on the disease symptomatology of the different pathogens in a specific area. To address this, a survey was conducted in 30 wine and table grape vineyards in summer, marginal and winter rainfall regions of South Africa. Apart from Eutypa lata , which occurred only in the winter rainfall region, Phaeomoniella chlamydospora , species of Phaeoacremonium , Botryosphaeriaceae and Phomopsis occurred in all regions surveyed. The incidence of the fungal genera and species associated with trunk disease varied between regions, with overlapping symptom profiles that differed based on the climatic region. These findings suggest that symptom-based disease diagnosis alone is unreliable and that distribution and symptomatology of grapevine trunk pathogens are strongly influenced by climatic conditions in a specific production region.

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.

Improved leaf pruning reduces development of stem cankers caused by grey mould in greenhouse tomatoes

Botrytis cinerea, the causal agent of grey mould, is considered as a major burden on greenhouse tomato production. In heated greenhouses, where leaf pruning is a routine practice and microclimatic conditions are favourable for grey mould development, infections of the pruning wounds result in stem cankers that can rapidly kill the plants. Chemical control is not always sufficiently effective and growers face increasing demands for reducing their dependency on pesticides. Several techniques can be used for the removal of leaves. They differ mainly on the presence or absence and the size of petiole stubs remaining on the stems after pruning. In this study, leaf pruning techniques were compared in an experimental greenhouse and the results validated in four commercial greenhouses, in a variety of agronomic conditions and in various situations of inoculum pressure. All experiments clearly showed that a careful removal of the leaves without leaving any petiole stubs on the stems can significantly decrease the incidence of stem cankers even under high disease pressure. As up to 10-fold differences were observed, this suggests the possibility of improving pruning practices in tomato greenhouses by removing leaves systematically close to the stem. This environmentally-friendly cultural practice appears compatible for integration with other preventative methods for the objective of sustainable crop protection in greenhouse tomatoes.

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.

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

Trunk diseases diminish vineyard longevity and productivity in nearly every raisin, table, and wine grape production region worldwide. Fungi causing these diseases infect primarily through pruning wounds. One way to control these diseases is to protect pruning wounds with fungicide applications, which can be problematic because of the limited number of registered products; the difficulty for these products to control numerous taxonomically unrelated organisms; the challenge of these products to protect for the entire period of wound susceptibility; and the difficulties and costs associated with hand application of protection treatments. Our goal was to compare the susceptibility of grapevine pruning wounds to various fungi associated with trunk diseases and to evaluate the efficacy of selected fungicides to control these pathogens when applied as pruning wound protectants. The study was conducted over two consecutive years in two separate vineyards in Sonoma and Colusa counties, California. Nine pathogenic fungi were tested: <i>Eutypa lata, Botryosphaeria dothidea, Diplodia seriata, Dothiorella viticola, Lasodiplodia theobromae, Phaeomoniella chlamydospora, Pleurostomophora richardsiae, Togninia minima</i>, and <i>Phaeoacremonium parasiticum</i>. Results showed differences in the infection rates of pruning wounds by these fungi. Species of Botryosphaeriaceae were the most infectious, <i>T. minima</i>, <i>P. parasiticum</i>, <i>P. richardsiae,</i> and <i>E. lata</i> were less infectious, and <i>Pa. chlamydospora</i> was intermediate. Four selected fungicides were tested: 1% Topsin M, Biopaste (5% boric acid in a wound-sealing paste), 1% Cabrio EG, and Garrison. Although results highlight the difficulty of these products to control the entire spectrum of pathogens efficiently, Topsin M was overall the most efficacious product.

Influence of Bemisia tabaci (Gennadius) and Myzus persicae (Sulzer) as preys on biological characteristics of Phrynocaria congener (Billberg).

Pasting of the pruning wounds of grapevines with Tricho-XP, a commercial formulation containing Trichoderma viride and Paecilomyces lecanii, immediately after foundation pruning along with soil application @ 5 g/vine mixed with 245g cattle manure, and spray on the vines @ 1.0 % has shown the potential to reduce dead wood and enhance bud sprouting in Tas-A-Ganesh grapes. Further, five isolates of Trichoderma exhibited differences in their antagonism as well as ability to minimize dead wood formation and enhance bud sprouting. T. harzianum 5R exhibited maximum in vitro antagonism of Lasiodiplodia theobromae and was the most effective in minimizing dead wood formation in grapevines. This isolate was able to grow and inhibit radial growth of L. theobromae even at higher temperature of 36°C.

Ceratocystis species: emerging pathogens of non-native plantation Eucalyptus and Acacia species

The fungal genus Ceratocystis includes many economically important tree pathogens. Until the 1980s, this genus of plant pathogens was not known from non-native plantation-grown forestry species. However, during the course of the last 20 years, a number of reports have been made of Ceratocystis spp. causing death of non-native plantation-grown forestry species from several locations worldwide. Affected trees include both Australian Acacia spp. and Eucalyptus spp. The first report of disease caused by a Ceratocystis sp. on Eucalyptus was made less than 10 years ago from Central Africa and, shortly thereafter, the disease was reported from Brazil. Subsequently, a number of other reports of Ceratocystis diseases have emerged from Africa, South America and Asia. These diseases are characterised by rapid wilt and death of trees and they have been reported to affect coppice stems as well as mature trees. In many cases, infection is associated with pruning wounds or other mechanical damage. The causal agent has been reported as Ceratocystis fimbriata s.l., but the Eucalyptus pathogen most likely represents a number of previously undescribed species. Ceratocystis spp. are vectored by wood- and bark-associated insects and typically those that visit fresh wounds, which act as infection courts. The fungi infect woody tissue and produce fruity aromas, which are attractive to insects. In this way, they can easily spread between countries and continents, thus posing a considerable quarantine threat. The biology of Ceratocystis spp. is such that diseases caused by this group of fungi are likely to become more common in the future.

Susceptibility of silver birch pruning wounds to infection by white-rot fungus (Chondrostereum purpureum), a potential bioherbicide

We artificially inoculated pruning wounds of silver birch (Betula pendula Roth) to study seasonal variation in their vulnerability to infection by the fungal decomposer Chondrostereum purpureum (Pers. ex Fr.) Pouzar. This information is critical to the assessment of incidental infection risks in areas where C. purpureum may be used as a bioherbicide. On seven monthly occasions between April and October 2005, 30 birch trees were pruned to yield a total of 210 experimental trees. On each occasion, 10 trees were inoculated immediately with C. purpureum mycelium, 10 were inoculated with blank inoculum and 10 were only pruned. In the summer of 2007, a survey of 129 experimental trees showed that pruning wounds were most susceptible to infection during May. Treatment with C. purpureum at other times during the growing season also increased the extent of discoloration or decay but the effect was considerably less.

Pruning and cypress canker in New Zealand

In New Zealand, the planting of cypresses is hindered by cypress canker disease caused by Seiridium cardinale (W.W. Wagener) B. Sutton & I.A.S. Gibson and S. cupressi (Guba) Boesew.). Pruning is widely practiced in established plantations to improve timber quality, although knowledge of its effect on disease incidence remains imperfect. Stubs of freshly cut branches on 275 trees of Cupressus macrocarpa Gordon & Leyland were inoculated with an isolate of either S. cardinale or S. cupressi to investigate the potential for pruning wounds to act as infection courts. In total, 75% of stubs inoculated at the edge, and 60% of those inoculated at the centre, became infected and produced stem cankers after 1 year, whereas cankers were formed on only 2% of non-inoculated control stubs. Incidence of cankers differed significantly between isolates. A second experiment was conducted at the same site 2 years later when stand infestation had increased, this time without inoculating but instead relying on ambient field inoculum. Stem cankers were produced on 11% of stubs on 162 trees, as a result of natural infection following pruning during periods of light rain in spring and summer. This investigation confirmed the ability of Seiridium species to invade through fresh pruning wounds on C. macrocarpa, and strengthens the recommendation to remove diseased plant material early, to maintain a low level of natural-spore inoculum within stands. It also indicates that pruning during wet weather should be avoided. Cleaning or disinfecting implements among trees may also be appropriate when conducting silvicultural operations in diseased plantations.

TREE STEM GROWTH RING ANALYSIS—A CASE STUDY INVOLVING A MATURE CEDAR AND HOUSING DEVELOPMENT

Summary Increment core samples taken from the main stem of cedar tree (Cedrus sp) showed unusual ring width sequences that could not be explained from detailed microscopic analysis. A full trunk disc was obtained and the ring patterns investigated. The occurrence of false and locally absent rings was determined and the rings dated. The beginning of the unusual ring width sequences coincided with development of the land around the trees for housing in the late 1970s. Root damage and/or changes in the rhizosphere associated with the housing development are likely to have been responsible for the period of abnormally slow and erratic growth of the tree. Despite a near twenty-year period of slow and erratic growth the tree had returned to a reasonable, consistent and regular growth ring width sequence by the late 1990s. Caution should be exercised when undertaking ring counts and interpreting ring widths using increment core samples taken from trees that may have suffered traumas as a result of root or soil damage or from the trunks of trees directly below large pruning wounds or lost branches. Similar caution should be exercised when interpreting increment core samples showing unusual resin ducts (cedars and some other conifers) or erratic ring widths.

Protection of grapevine pruning wounds from infection byEutypa lata

Background and Aims: Eutypa dieback is a major threat to the sustainability and productivity of the viticulture industry worldwide. The fungicide benomyl has been the most effective treatment to protect wounds against infection by ascospores of Eutypa lata and to control eutypa dieback. However, because of the withdrawal of benomyl from the market, there is a need to develop alternatives to protect pruning wounds. Methods and Results: Twenty-five compounds were evaluated in laboratory experiments and field trials. A selection of the compounds effective at inhibiting germination and/or mycelial growth in the laboratory were further evaluated in the field. Of the 15 fungicides tested, carbendazim was the most effective in reducing colonisation of pruning wounds by E. lata in the field. Other fungicides, including fluazinam, pyrimethanil and pyraclostrobin, reduced colonisation of wounds by E. lata but require further evaluation at higher concentrations. Physical barriers such as acrylic paint (with or without fungicides) and a commercial tree wound paste formulated with fungicides (Garrison) also protected pruning wounds from infection by E. lata. Conclusions: Fungicides and physical barriers have been identified for the control of eutypa dieback in grapevines. The registration of Bavistin (carbendazim) and Garrison is being sought for use on pruning wounds on grapevines in Australia. Significance of the Study: Protection of pruning wounds is essential for the management of eutypa dieback in grapevines. Identification of alternative methods for disease control will provide significant economic benefits for the grapegrowing industry.

Studies on the susceptibility of pruning wounds to infection by fungi involved in grapevine wood diseases in Italy

The susceptibility of grapevine annual pruning wounds to Phaeomoniella chlamydospora , Phaeoacremonium aleophilum and Diplodia seriata was investigated over three years (2005–2007) in a 15 year-old vineyard, cv. Sauvignon blanc. Vines were pruned each year in January, February and March and the wounds were inoculated weekly with conidial suspensions, and with sterile water as a control. Penetration of the fungi into the wood was assessed after 4 weeks by plating pieces of host tissue on agar medium. The susceptibility of annual pruning wounds, expressed as the infection percentages of inoculated spurs, varied with both the trial year and the fungus inoculated. Average infection percentages of inoculated spurs in the three years were respectively 14.7, 38.5 and 50.9% for Pa. chlamydospora , 31.7, 32.2 and 49.4% for Pm. aleophilum and 84.2, 43.8 and 40.9% for D. seriata . The period of pruning was significant for the infection percentages of all fungi in 2005, and for D. seriata in 2006. Natural infection of control spurs by Pa. chlamydospora (2, 4.4, and 11.7% of spurs in the three years respectively) and by Pm. aleophilum (0.3, 1.8, and 6.4%) began when average weekly temperatures stabilized around 10°C, while infection by D. seriata (12.2, 12 and 18.3% in the same period) occurred even below that threshold. Higher infection percentages of both artificially and naturally infected spurs in 2007 were probably due to the higher temperatures recorded in February and March (besides the use of a more efficient selective medium for the isolation of Pa. chlamydospora and Pm. aleophilum ). Only artificial infections with D. seriata showed an opposite trend that cannot be explained by the weather data. Infection of one-year-old wood appeared to be an important factor in disease spread. Spurs remained liable to infections with any of the fungi for up to 4 months after pruning, and isolation percentages could be fairly high also in late spring. As a consequence, the planning of pruning does not seem to be an effective means to counteract the wood diseases caused by these fungi.

Susceptibility of Grapevine Pruning Wounds and Symptom Development in Response to Infection by Phaeoacremonium aleophilum and Phaeomoniella chlamydospora.

Fresh to 10-month-old pruning wounds on grapevine cvs. Thompson Seedless and Cabernet Sauvignon were inoculated with Phaeoacremonium aleophilum or Phaeomoniella chlamydospora at approximately 1 × 106 spores/ml. Successful infection was determined by isolation of the pathogen from necrotic margins of cankers or from vascular discoloration assessed 4 months after each inoculation date. Disease incidence decreased as the length of time between pruning and inoculation increased; however, wounds remained susceptible for up to 4 months. Vascular discoloration was significantly less extensive in the noninoculated control than in inoculated spurs. Reduction of shoot length in both cultivars varied depending on pruning wound age at the time of inoculation. In a separate study, inoculation of fresh pruning wounds of Cabernet Sauvignon resulted in successful infection regardless of the time of pruning from February to December.

Response of Two Oak Species to Reduction Pruning Cuts

Reduction pruning cuts were used to prune Quercus virginiana (live oak) and Quercus Shumardii (shumard oak). One-half of the pruning wounds were harvested and dissected 3 years later to observe extent of discoloration in response to the pruning cut. Shumard oak did not limit discoloration as effectively as live oak. Discolored area in the wood increased with size of the pruning cut surface in shumard oak and less so in live oak. Dissections showed that the shape of the discolored area attenuated with depth. The branch connection morphology and response (branch–trunk aspect ratio, branch angle, release growth after pruning) appeared to influence discoloration pattern in reduction pruning. The angle of the reduction cut relative to the American National Standards Institute-recommended angle bisect method was not found to influence discoloration. Discoloration in the less efficient compartmentalizing species (Shumard oak) was related to cut surface area, but not to cut angle. There was no relationship between aspect ratio and discoloration in the 3 years after pruning. The data suggest that reduction cuts can be made back to lateral branches as small as one-third the diameter of the removed stem.

First Report of Botryosphaeria iberica and B. viticola Associated with Grapevine Decline in California.

Grapevine decline symptoms in California include dead spurs and cordon and trunk dieback due to canker formation in the vascular tissue. Seven Botryosphaeria spp. are known to be associated with grapevine cankers in California, viz. Botryosphaeria australis, B. dothidea, B. lutea, B. obtusa, B. parva, B. rhodina, and B. stevensii (3). Recently, B. iberica and B. viticola also were isolated from grapevine cankers in a field survey that was conducted throughout California. Identification was based on morphological comparisons along with DNA analyses with previously identified isolates from Spain (1,2): B. iberica (CBS115035, ex-type) and B. viticola (CBS117006 and CBS117009, ex-type). DNA sequences of the rDNA internal transcribed spacer region (ITSI-5.8S-ITS2), part of the β-tubulin gene (BT2), and part of the translation elongation factor 1-α gene (EF1-α) from B. iberica and B. viticola isolates from California were amplified using primers ITS4/ITS5, Bt2a/Bt2b, and EF-728F/EF-986R, respectively. All DNA sequences of B. iberica and B. viticola from California showed 99 to 100% homology with those previously identified and deposited in GenBank. B. iberica, isolated from grapevine cankers from San Luis Obispo County (central coast), formed colonies on potato dextrose agar (PDA) that were dark green with aerial mycelium, optimum growth at 20 to 25°C, and formed pycnidia after 15 days of incubation at 25°C. Conidia were brown, one-septate, oblong to ovoid with a rounded apex, and measured (20.1-) 22.5 to 23.5 (-27.1) × (8.1) 9.3 to 9.8 (-11.2) μm, length/width ratio = 2.4 (n = 60). B. viticola, isolated from grapevine cankers in Sonoma (north coast), San Luis Obispo, Santa Barbara (south coast), Riverside (southern California), and Yolo (Sacramento Valley) counties, formed colonies on PDA that were dark green to grayish with aerial mycelium, optimum growth at 25°C, and formed pycnidia after 2 weeks. Conidia were brown, one-septate, oval to oblong, and measured (16.6-) 19.3 to 20.3 (-23.5) × (8.1) 9.3 to 9.6 (-11.1) μm, length/width ratio = 2.1 (n = 60). Two isolates of each species were used to complete pathogenicity tests (B. iberica: ATCC MYA-4110, ATCC MYA-4111; B. viticola: ATCC MYA-4115, ATCC MYA-4116). Ten fresh pruning wounds on 15-year-old cv. Zinfandel vines were inoculated per isolate using 50 μl of a 5 × 106 conidia per ml suspension. Twenty control pruning wounds were inoculated with the same amount of sterile water. Twelve months after inoculation, all wood inoculated with B. iberica and B. viticola showed internal necrosis extending 35 to 50 and 30 to 35 mm from the point of inoculation, respectively. Necrosis and extent of vascular discoloration in infected wounds was significantly greater (P < 0.05) than in control inoculations (6.5 mm). B. iberica and B. viticola were reisolated from the necrotic region surrounding all inoculation sites. Representative isolates of B. iberica and B. viticola from California were deposited at the American Type Culture Collection (B. iberica: MYA-4110, MYA-4111; B. viticola: MYA-4112 to MYA-4116). Sequences from the studied DNA regions of all isolates were deposited at GenBank. To our knowledge, this is the first report implicating either species as a cause of grapevine decline in California and B. iberica as a pathogen of Vitis vinifera anywhere in the world.

Pathogenicity testing of lesser-known vascular fungi of grapevines

Several hyphomycetes were recently isolated from asymptomatic or symptomatic vascular tissues of grapevines showing Petri disease symptoms in South Africa. In most cases, their status as pathogens was unknown and pathogenicity studies were, therefore, conducted to determine their potential as decline pathogens. The fungi included Acremonium cf. charticola, Acremonium cf. ochraceum, Cadophora luteo-olivacea, Phialemonium cf. curvatum, Pleurostomophora richardsiae, Phaeoacremonium (Pm.) krajdenii, Pm. parasiticum, Pm. subulatum, Pm. venezuelense and Pm. viticola. Of these, Pm. parasiticum and Pm. viticola have been associated with Petri disease symptoms, although their pathogenicity has not been tested. Phaeomoniella (Pa.) chlamydospora and Pm. aleophilum, known to be involved in Petri disease and esca, were included as positive controls. Pathogenicity studies were conducted in glasshouse experiments where grapevine rootstocks were artificially inoculated, as well as in the field. Data obtained after 3 months from a glasshouse trial were difficult to interpret, due to the small lesions and similarity in disease expression among different species. However, Pa. chlamydospora produced the largest lesions and was by far the most aggressive pathogen. To supplement the glasshouse trial, grapevine trunks and pruning wounds of Vitis vinifera cv. Periquita were artificially inoculated in the field. Field trials, rated after 14 months, confirmed Pa. chlamydospora to be the most aggressive pathogen, since it produced the largest trunk and pruning wound lesions. Furthermore, it was re-isolated more frequently than any of the other fungi, especially from the pruning wounds. All the fungi were able to infect, colonise and produce lesions statistically different to those caused by the water control and the non-pathogen in the field trial.

Pycnoporus cinnabarinusis pathogenic on livingPaulowniatrees

Distinctive basidiomes of Pycnoporus sp. were observed on 5–6-year-old living Paulownia trees at two commercial plantations in Western Australia. The basidiomes were erupting through the bark, which readily peeled away to expose the rotting wood beneath. Based on internal transcribed spacer-polymerase chain reaction, the fungus was identified as Pycnoporus cinnabarinus. Under-bark inoculation of 3-year-old Paulownia fortunei trees in the glasshouse, with mycelium isolated from basidiomes on trees at the commercial plantations, resulted in the formation of dark lesions and the pathogen was re-isolated ahead of the lesion front. Benomyl and cyprodinil were the most effective fungicides at inhibiting the growth of mycelium in vitro. This is the first report of Pyc. cinnabarinus acting as a pathogen on Paulownia trees. It is likely that the pathogen enters living trees through pruning wounds or damage from sun scald. Further work is required to confirm methods of control in the field.

Evaluation of fungicides as potential grapevine pruning wound protectants againstBotryosphaeriaspecies

Protection of wounds against infection by trunk disease pathogens is the most efficient and cost-effective means to prevent grapevine trunk diseases. Studies done to determine the effectiveness of chemical pruning wound protectants have mostly focused on the control of Eutypa lata. However, other important wound pathogens, such as Phaeomoniella chlamydospora, Phaeoacremonium spp., Phomopsis spp. and species of Botryosphaeriaceae (including Botryosphaeria and aggregate genera), pose just as significant a threat to sustainable grape production. Fungicide sensitivity studies have been conducted for Pa. chlamydospora, P. viticola and E. lata. However, no such studies have been conducted for the pathogenic species of Botryosphaeriaceae from grapevines in South Africa. Ten fungicides were, therefore, tested in vitro for their efficacy on mycelial inhibition of the four most common or pathogenic species of Botryosphaeriaceae in South Africa, ‘B.’ obtusa, Neofusicoccum australe, N. parvum and Lasiodiplodia theobromae. Iprodione, pyrimethanil, copper ammonium acetate, kresoxim-methyl and boscalidwere ineffective in inhibiting themycelial growth at the highest concentrations tested (20 μg/mL for copper ammonium acetate, 5 μg/mL for other agents tested). Benomyl, tebuconazole, prochloraz manganese chloride and flusilazole were the most effective fungicides with EC50 values for the different species ranging from 0.36–0.55, 0.07–0.17, 0.07–1.15 and 0.04–0.36 μg/mL, respectively. These fungicides, except prochloraz manganese chloride, are registered for use on grapes in South Africa and were also reported to be effective against Pa. chlamydospora, P. viticola and E. lata. Results from bioassays on 1-year-old Chenin Blanc grapevine shoots indicated that benomyl, tebuconazole and prochloraz manganese chloride were most effective in limiting lesion length in pruning wounds that were inoculated with species of Botryosphaeriaceae after fungicide treatment. The bioassay findings were, however, inconclusive due to low and varied re-isolation incidences. Benomyl, tebuconazole, prochloraz manganese chloride and flusilazole can be identified as fungicides to be evaluated as pruning wound protectants in additional bioassays and vineyard trials against species of Botryosphaeriaceae as well as the other grapevine trunk disease pathogens.

Penetration of &lt;i&gt;Trichoderma harzianum&lt;/i&gt; into grapevine wood from treated pruning wounds

Vinevaxtrade; (containing a mixture of strains of the fungus Trichoderma harzianum) is normally applied as soon as possible after grapevine pruning However using a range of six timings after pruning from immediate to 4 days later it was shown that the best penetration of the fungi into the wood was with treatment at approximately 5 h after pruning A novel method of measuring penetration and vigour of the growth of Trichoderma spp into grape wood is described A second trial using a range of concentrations of Vinevaxtrade; (at and below label rates) was applied as a general cover spray over dormant pruned vines The percentage incidence and vigour of penetration of the T harzianum into canes was concentration dependent and lower than the targeted handapplied treatment earlier in the season Therefore targeted timely applications of the product appear to be best for good wood penetration of T harzianum

Clavibacter michiganensis subsp. michiganensis

<i>Clavibacter michiganensis</i> subsp. <i>michiganensis</i>