Apple blotch (AB) is a major disease of apple in Asia and recently emerged in Europe and the USA. It is caused by the fungus Diplocarpon coronariae (Dc) (formerly: Marssonina coronaria; teleomorph: Diplocarpon mali) and leads to severe defoliation of apple trees in late summer resulting in reduced yield and fruit quality. To develop effective disease management strategies, a sound knowledge of the pathogen’s biology is crucial. Data on the early phase of disease development is scarce: no data on spore dispersal in Europe is available. We developed a highly sensitive TaqMan qPCR method to quantify Dc conidia in spore trap samples. We monitored temporal and spatial dispersal of conidia of Dc, and progress of AB in spring and early summer in an extensively managed apple orchard in Switzerland in 2019 and 2020. Our results show that Dc overwinters in leaf litter and spore dispersal and primary infections occur in late April and early May. We provide the first results describing early-season dispersal of conidia of Dc, which, combined with the observed disease progress, helps to understand the disease dynamics and will be a basis for improved disease forecast models. Using the new qPCR method, we detected Dc in buds, on bark, and on fruit mummies, suggesting that several apple tissues may serve as overwintering habitats for the fungus, in addition to fallen leaves.

Limited data regarding the resources and methods used by organic fruit growers to learn about production practices are available, even though this information is crucial to improving the efficacy of knowledge transfer. Therefore, a survey to gain information from knowledge networks dealing with organic fruit production about their structural organisation, tasks and methods of communication was carried out in twenty-one countries from Europe and the Mediterranean basin. A total of 56 networks representing about 42,500 professionals were identified as a result of the survey. The vast majority of them were only active at the regional or national level and were composed of farmers, advisors and researchers. About 3/4 of the networks were developing improved strategies for agronomic practices and about half of them were also involved in different knowledge-transfer activities between their members. Personal contact was the most used method to exchange and disseminate information within the networks as well as to elaborate improved strategies. The findings were analysed in view of the methods and practices commonly used to share both explicit (scientific) and implicit (practical) knowledge among practitioners. It was concluded that knowledge networks play an important role in the development of more resilient organic cropping systems, frequently making organic fruit growers the drivers of innovation. Networking for knowledge exchange was considered a process that encourages the active involvement of farmers in experimentation and innovation applying a method of knowledge sharing that is rooted in the very foundation of organic philosophy. Some recommendations and future research were suggested to further foster the development and functioning of networks for knowledge exchange.

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Apple blotch (AB) is a major disease of apples in Asia and recently also emerging in Europe and the USA. It is caused by the fungus Diplocarpon coronariae (Dc) (formerly: Marssonina coronaria; teleomorph: Diplocarpon mali) and leads to severe defoliation of apple trees in late summer and thus to reduced yield and fruit quality. To develop effective crop protection strategies, a sound knowledge of the pathogen's biology is crucial. However, especially data on the early phase of disease development is scarce, and no data on spore dispersal for Europe is available. In this study, we assessed different spore traps for their capacity to capture Dc spores, and we developed a highly sensitive TaqMan qPCR method to quantify Dc conidia in spore trap samples. With these tools, we monitored the temporal and spatial spore dispersal and disease progress in spring and early summer in an extensively managed apple orchard in Switzerland in 2019 and 2020. Our results show that Dc overwinters in leaf litter and that spore dispersal and primary infections occur already in late April and beginning of May. We provide the first results on early-season spore dispersal of Dc, which, combined with the observed disease progress, helps to understand the disease dynamics and improve disease forecast models. Using the new qPCR method, we finally detected Dc in buds, on bark and on fruit mummies, suggesting that these apple organs may serve as additional overwintering habitats for the fungus.

There is limited data regarding the specific problems faced by organic fruit growers when dealing with plant protection, particularly at a European Union level, though some general knowledge about pest and disease incidence can be found. Such information is crucial to improve the efficacy of a targeted knowledge transfer to organic fruit growers and advisors aiming at an increased adoption of innovative practices. A survey was thus carried out in seventeen European countries (16 EU member states and Switzerland), within the framework of the EU-funded project BIOFRUITNET, aiming at filling this knowledge gap also in terms of research needs. A questionnaire including a section about general aspects of orchard management (functional biodiversity, fertilization management, varietal/rootstock selection) and a section specifically dedicated to pest and disease occurrence and management in organic orchards was utilized to interview about 250 professionals (farmers and advisors), 155 of which were involved in pome fruits (including apple and pear) production. The analysis of the answers related to plant protection pointed out a varied situation about pest and disease occurrence in apple and pear orchards across Europe, though related to the zonal location of the respondent. However, more than 50% of respondents generally considered just few among the most damaging ones, normally co-occurring in the orchards. Interestingly, regardless of the respondents’ nationality or zonal location, more pests than diseases were indicated as relevant agents threatening organic pome fruits production. Nevertheless, only few measures promoting functional biodiversity in the orchards resulted in being broadly implemented in all regions. The analysis of the data underlines the strong demand for the development of a toolbox of measures that can be integrated successfully into the general orchard management strategy including the successful enhancement of functional or general biodiversity.