The quality and quantity of nut production are fundamental to the economic viability of chestnut cultivation, yet recent reports indicate that severe damage due to moulds represents a significant problem for growers. We carried out an investigation of the agents of chestnut rot and internal fruit damage in three orchards in Italy. Black and brown rot, as well as insect damage, were found in all the areas examined. Brown rot appeared to be the main cause of damage, affecting 8% to 49% and 2% to 24% of nuts collected from the ground and from burrs, respectively. With respect to morphology and DNA sequencing analyses, fungal isolates obtained from brown rot were homologous with Gnomoniopsis sp. obtained from Dryocosmus kuriphilus (Yasumatsu) galls and with Gnomoniopsis castanea and Gnomoniopsis smithogilvyi described on chestnut in Italy and Australia, respectively. The same fungus was also isolated from the bark of one- and two-years-old healthy shoots at each site, supporting the endophytic behaviour of this rot agent. Brown rot symptoms on nuts associated with Gnomoniopsis sp. corresponded with those previously described by several authors and referred to as Phoma or Phomopsis endogena, suggesting a relationship between these fungi and Gnomoniopsis sp. It is to notice that the escalation of brown rot damage in Italy followed several periods of drought and probably the recent invasion of D. kuriphilus, both stress factors for chestnut trees.

A retrospective examination of early pest and disease outbreaks, such as ink disease, offers new insights into their impact on ecosystems and landscapes. Ink disease, caused by Phytophthora spp., is one of the most destructive diseases affecting Castanea sativa Mill. It first appeared in Europe in the early 18th century, with the initial recorded case in Italy (Piedmont) dating back to 1845. However, its spread instilled significant concerns in several chestnut-growing regions primarily devoted to fruit production. In 1938, a comprehensive assessment of Phytophthora xcambivora outbreaks was conducted in the Bolognese Apennines (Italy), providing a detailed overview of chestnut cultivation status. Thirty-six disease foci were documented, and laboratory tests confirmed the presence of ink disease. To understand the disease’s impact on chestnut ecosystem and landscape over the past 85 years, the 1938 sites were revisited to assess chestnut persistence and phytosanitary status, with Phytophthora species detected using isolation and molecular techniques. Monitoring data revealed that C. sativa still thrives in all but one site, with its wood seemingly able to coexist in dynamic equilibrium with the disease. While P. xcambivora was still detected in several foci, the extent of damage appeared limited. The potential for natural control, likely influenced by the complexity of soil biota, along with the natural spread of hypovirulence in chestnut blight and biological control of the Asian chestnut gall wasp, could explain the continued presence of chestnut in the investigated area and potentially throughout the Italian chestnut range, despite nearly two centuries of ink disease prevalence. Nevertheless, ongoing monitoring is essential to dynamically comprehend the factors at play and their efficacy, particularly in the context of climate change and the possible spread of other Phytophthora species. The survival of chestnut ecosystems amidst ink disease underscores the preservation of the economic, ecological, and landscape values associated with these woodlands.

The spread of Hymenoscyphus fraxineus has been causing great concern regarding the survival of European ash (Fraxinus excelsior) throughout Europe since the 1990s. The disease was first recorded in Trentino (southern Alps, Italy) in 2012 and has spread throughout the mountain landscape, where ash trees are scattered in small and isolated stands in different valleys. The status of the disease was checked by monitoring the damage to natural regeneration and adult trees in 90 sites spread over the whole region. The survey confirmed the complete colonization by the pathogen of the whole investigated area, with high levels of damage to both young and adult ash trees. Regeneration (both seedlings and saplings) was observed to be affected by the fungus in 88 plots out of 90. Out of 4486 examined young European ashes, 2261 (50.4%) were affected and 789 (17.6%) were already dead. Ten of the 384 assayed flowering ashes (Fraxinus ornus) showed symptoms on branches and apical stems, similar to those observed for European ash. Isolation and molecular analysis proved the presence of the fungus on both symptomatic European and flowering ashes. The examined 386 adult trees showed different levels of damage, sometimes reaching more than 75% of the crown. Some individual trees (42) growing close to severely damaged trees appeared fully healthy, which suggests the possible existence of some resistant/tolerant individuals in the examined populations.

The European chestnut characterizes both the landscape and economy of mountainous Italian areas. In recent years, new canopy disorders have been reported: “chestnut yellows”, often ascribed to phytoplasma and/or nutrient deficiency, and “chestnut mosaic”, associated with a virus (ChMV). Therefore, research was carried out in four Italian regions to describe the two symptomatic frames and assess their etiology. Surveys were conducted on 101 chestnut trees (23 with mosaic, 38 with yellowing, and 40 without symptoms). The phytosanitary status was monitored, and the new canopy disorders were detected, distinguishing between yellowing and mosaic. Moreover, leaf samples were collected for molecular and nutrient analyses. No phytoplasma infection was recorded, while ChMV was detected in 91.3% of samples with mosaic symptoms, 31.6% of yellowing samples, and 30.0% of asymptomatic samples. Yellowing was associated with Mn deficiency. On the other hand, ChMV-infected and healthy leaves had similar mineral contents, showing that mosaic symptoms are induced by the virus. Both disorders negatively affected photosynthesis efficiency. These phytosanitary problems are present in Italian chestnut woods and cause local effects, and a relationship with other biotic and abiotic factors can be hypothesized. Considering the increase in new records, these symptoms represent an emerging issue whose impact and spread need to be further monitored.