The grapevine trunk diseases Eutypa and Botryosphaeria dieback threaten the sustainability of vineyards worldwide. This study aimed to develop practical and efficient wound protection strategies, which will lead to widespread adoption of preventative control for these diseases and increased longevity of vineyards. Five fungicides (tebuconazole, carbendazim, fluazinam, mancozeb, and flusilazole) were evaluated for efficacy against Eutypa lata and Neofusicoccum luteum infection on pruning wounds of ‘Sauvignon blanc’ in a New Zealand vineyard. All five fungicides controlled infection by both pathogens to varying degrees, with mean percent disease control of 70 to 90% for E. lata and 33 to 93% for N. luteum. This has led to the first known registration of a fungicide, fluazinam (Gem), for simultaneous control of both Eutypa and Botryosphaeria dieback. Furthermore, application of carbendazim with tractor-driven sprayers provided similar control of E. lata and N. luteum to that when applied by hand with a paintbrush. This constitutes the first report of Botryosphaeria dieback control with fungicides applied with tractor-driven sprayers.

Botrytis bunch rot of grapes (BBR) causes substantial crop and wine quality issues globally. Past and present foundations for BBR control are based upon synthetic fungicides and varying forms of canopy management. Many authors regard the continued dependence on fungicides as unsustainable and have urged greater deployment of cultural, biological and nutritional strategies. However, in contrast to organic wine production, the uptake of alternative strategies in conventional vineyards has been slow based on cost and perceived reliability issues. This review summarises research from many different wine growing regions in New Zealand with the aim of demonstrating how traditional and newly developed cultural control practices have cost-effectively reduced BBR. In addition to reviewing traditional cultural practices (e.g., leaf removal), mechanical tools are described that remove floral trash and mechanically shake the vines. Multi-omics has improved our knowledge of the underlying changes to grape berries after mechanical shaking. Exogenous applications of calcium may correct calcium deficiencies in the berry skin and reduce BBR but the outcome varies between cultivar and regions. Nitrogen aids in grapevine defence against BBR but remains a complex and difficult nutrient to manage. The sustainable growth of organics and The European Green Deal will stimulate researchers to evaluate new combinations of non-chemical BBR strategies in the next decade.

Nitrogen is an important macronutrient for grapevines influencing a number of metabolic pathways and plant structures This review provides a summary of some direct and indirect effects of nitrogen fertilisation on bunch rot incidence in the field Direct changes due to increased nitrogen nutrition include greater thickness of the wax on berry surfaces and increased concentrations of the biochemical defence compounds produced in them Indirect changes that result from increased nitrogen include development of tighter bunches and denser canopies As integrated management systems become more complex a better understanding of different components such as nitrogen nutrition is required to allow vineyard managers to make informed decisions on how potential changes to current practices may influence disease and berry quality parameters

The percentage of detached grape berries inoculated in the laboratory that became infected by Botrytis cinerea during ripening was correlated with increasing sugar concentration and increasing yeast assimilable nitrogen (YAN) concentration These factors could not be separated to provide a causal relationship between YAN and berries with disease due to the close relationship that existed between sugar concentration YAN vine development and time Wounding increased the percentage of berries with disease particularly when the berries were immature These findings do not support the hypothesis that the inherent susceptibility of grape berries to botrytis infection increases with increasing YAN Field observations by growers that nitrogen fertiliser increases bunch rot may be due to nitrogen causing increased canopy density which in turn causes a microclimate more conducive to the development of botrytis bunch rot

For a deeper understanding of grapevine trunk disease (GTD) in New Zealand, a cheap, rapid, sensitive method for identifying within-vine microbial communities is required. Wood tissue from grapevine trunks was collected and three different DNA extraction methods were compared: a cetyltrimethylammonium bromide (CTAB) method, the Geneaid Plant Genomic DNA Mini Kit and the Qiagen DNeasy Plant Mini Kit. DNA samples from the CTAB and Geneaid methods were used for MiSeq DNA metabarcoding targeting the ribosomal internal transcribed spacer 1 (ITS1) region. DNA produced by the CTAB method was of a greater quantity and quality than for the other two methods, although the majority of the DNA samples provided polymerase chain reaction (PCR) amplification of fungal DNA sequences. Fungal metabarcoding profiles from the CTAB and Geneaid samples indicated the presence of fungi normally associated with GTD in New Zealand. The CTAB method was chosen for subsequent work due to its low-cost, simplicity and effective detection of typical GTD fungi. The complete process of sampling through to metabarcoding is now used annually as part of a wider ecological study, screening more than 600 vines at 12 Marlborough vineyards.