Identification, pathogenicity and distribution of the causal agents of dieback in avocado orchards in Spain

An increased incidence of dieback from branches in several avocado orchards in southern Spain was observed in 2014. Surveys were conducted from May to October 2014, sampling the affected branches to isolate the causal agents. A total of 68 fungal isolates, recovered from ten avocado orchards, were identified, by morphological characterisation and DNA sequencing, as belonging to the genera: Neofusicoccum parvum (50%), Colletotrichum gloeosporioides (17.6%), Neofusicoccum luteum (16.2%), Neofusicoccum australe (13.2%), Neofusicoccum mediterraneum (1.5%) and Lasiodiplodia theobromae (1.5%). A decreasing level of virulence in artificial inoculations on avocado plants was observed in N. parvum, N. luteum, N. mediterraneum, N. australe, C. gloeosporioides and L. theobromae, there were significant differences among N. parvum and the rest of species of this genus, and significant differences were only observed between N. luteum and C. gloeosporioides. The geographical distribution of N. parvum and N. Luteum covers different areas, while C. gloeosporioides and N. australe are located only in the areas around Benamocarra and Vélez-Málaga (southern Spain), while N. mediterraneum and L. theobromae appear only occasionally. This is the first study of avocado branch cankers in Spain which identifies the causal agents and establishes their pathogenicity groups, with N. parvum as the most important causal agent of avocado dieback in this area.

Pruning Wound Protection Strategies for Simultaneous Control of Eutypa and Botryosphaeria Dieback in New Zealand

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.

Characterization and Pathogenicity of Botryosphaeriaceae Species Isolated from Almond Trees on the Island of Mallorca (Spain)

In this study, 31 almond orchards with trees showing severe decline symptoms were surveyed from 2009 to 2014 on the island of Mallorca (Spain). In all, 45 Botryosphaeriaceae isolates were collected and characterized based on phenotypical features and comparisons of DNA sequence data of the nuclear ribosomal DNA-internal transcribed spacer region and elongation factor 1-α gene. Five species were identified as Diplodia olivarum, D. seriata, Neofusicoccum luteum, N. mediterraneum, and N. parvum. Pathogenicity tests were performed on four cultivars (‘Pons’, ‘Vivot’, ‘Jordi’, and ‘Ferragnes’) under field conditions for two consecutive years (2013 to 2014), and confirmed that all five species cause canker and dieback of almond, with Neofusicoccum spp. more virulent than Diplodia spp. in both years. Jordi was less sensitive to fungal infection in 2013. First reports from almond in Spain include N. mediterraneum and N. luteum.