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.

A series of experiments using potted plants in a glasshouse detached laterals in the laboratory and trees in the fi eld were undertaken to study wound size and number of Neonectria ditissima conidia required to produce European canker infections on freshlymade branch wounds in the apple cultivars Royal Gala and Scilate Th e wound types were needle and pin injuries rasp wounds and pruning cuts Spore concentrations from 102 to 106 conidia/ml and two inoculation methods (droplet and mist) were used Disease expression varied for the different assay types probably due to the conduciveness for infection of the diff erent incubation conditions Overall there was little eff ect on pathogen colonisation and lesion development based on injury type inoculation method or spore concentration >103 conidia/ml For freshlymade wounds such as pruning cuts or rasp wounds only three conidia were required for infection initiation in the glasshouse under highly conducive conditions 12 conidia in the laboratory on detached shoots and 10 to 30 conidia in the fi eld

Leaf scar wounds are important sites for Neonectria ditissima infection of apple trees Monitoring leaf fall in Scilate/Envy and Braeburn trees to estimate leaf scar wound presence showed maximum leaf scar incidence occurred in June (early winter) Wounds detected in New Zealand apple orchards were bud scale scars fruit thinning and picking wounds leaf scars and pruning cuts Picking wounds are caused during harvest where the pedicel is detached from the shoot Susceptibility of these different types of wounds was determined using artificial inoculation of N ditissima conidia during the season Pruning cut wounds were the most susceptible followed by fruit picking and thinning wounds and the least susceptible were leaf scar wounds No infections were observed when bud scale wounds were inoculated There was no difference in wound susceptibility between cultivars but overall Scilate/Envy wounds developed more lesions than Braeburn wounds

This research has demonstrated that fungicides applied after winter pruning can protect vines from infection by conidia of three botryosphaeriaceous species.

New Zealand pipfruit crops require postharvest fungicides for control of European canker, caused by Neonectria ditissima. Fungicide efficacy trials to protect leaf scars from N. ditissima infections were conducted during autumn 2013 and 2014. Disease control of artificially inoculated leaf scars was achieved by single applications of copper oxychloride and copper oxide, but not copper hydroxide, applied at 4.3, 1.1 and 0.6 kg elemental copper/ ha respectively. Control of leaf scar infections by copper oxide (0.65 and 0.95 kg elemental copper/ha) was similar to control by captan. Leaf scars (0-10 days old) remained susceptible to infections up to 10 days after leaf fall; disease control was achieved by re-distribution of copper and captan fungicides onto new leaf scars. Disease control using copper oxide was consistent and similar to control using captan. The copper product, and concentration of elemental copper, are important for successful control of leaf scar infections by N. ditissima.