Bark and ambrosia beetles (Coleoptera: Curculionidae: Scolytinae) are major pests of agricultural and forest systems and include some species which attack hazelnut (Corylus avellana L.) as well. Although hazelnut cultivation is increasingly threatened by insect and mite pests, yet little is known about how management practices can reduce infestations. This study investigated bark and ambrosia beetles in hazelnut orchards from two highly productive areas: Viterbo district (central Italy) and Samegrelo-Zemo Svaneti region (Republic of Georgia). Three phytosanitary management strategies were compared across 2023–2024: Integrated Pest Management, organic farming, and renaturalised orchards. Monitoring also evaluated three ethanol-baited trap designs: three designs in Italy (handmade red funnel [BR] and bottle [TT] and commercial multi-funnel [MF]) and only TT in Georgia. Anisandrus dispar, Hypothenemus eruditus, Xyleborinus saxesenii, and Xylosandrus germanus were detected in both countries, while Xyleborus monographus occurred only in Italy. Xyleborinus saxesenii was the dominant species in both regions. Beetle populations differed among management strategies, being lowest in organic orchards and highest in integrated and renaturalised systems. Trap performance also varied, with BR consistently outperforming commercial MF. These findings highlight the influence of management and monitoring tools on scolytine populations, offering practical insights for sustainable hazelnut production.

Fungal trunk disease (FTD) poses a significant threat to hazelnut (Corylus avellana L.) production worldwide. In Chile, the fungus Diplodia mutila, from the Botryosphaeriaceae family, has been frequently identified causing this disease in the Maule and Ñuble Regions. However, control measures for D. mutila remain limited. This research aimed to evaluate the effectiveness of chemical and biological fungicides against D. mutila under in vitro, controlled pot experiment, and field conditions. An in vitro screening of 30 fungicides was conducted. The effectiveness was assessed by measuring the length of vascular lesions in hazelnut branches inoculated with D. mutila mycelium disks under controlled and field conditions. Field trials were conducted in a hazelnut orchard in Ñiquén, Ñuble Region, Chile. The results showed that three biological and five chemical fungicides were selected in vitro with >31% inhibition after 14 days. In pot experiments, all fungicides reduced necrotic lesions on branches by 32% to 61%. In field experiments, the most effective systemic fungicides were fluopyram/tebuconazole, fluxapyroxad/pyraclostrobin, and tebuconazole, while the effectiveness of antagonists Pseudomonas protegens ChC7 and Bacillus subtilis QST713 varied with seasonal temperatures. Effective conventional and biological fungicides against D. mutila could be integrated into disease management programs to protect hazelnut wounds from infections.

Hazelnut (Corylus avellana L.) is the second most cultivated nut crop in Chile. Pathogens associated with fungal trunk diseases (FTD) pose a serious threat to this crop, because these fungi colonize the wood causing loss of productivity and eventually death of the plants (Martino et al., 2025). During Spring 2018 and 2020, FTD symptoms such as wood necrosis, vascular discoloration of branches, cankers, and wilted branches were detected in a survey conducted in 24 hazelnut orchards located between Maule and Araucanía regions, Chile (Moya-Elizondo et al., 2023). Wood pieces (3 mm x 5 mm) were removed from the edge of necrotic canker lesions, disinfected with 2% NaOCl, rinsed twice with sterile distilled water, and dried on sterile absorbent paper. Tissue pieces were placed on potato dextrose agar (PDA) supplemented with streptomycin sulphate (200 mg L⁻¹) and incubated at 25°C in darkness for five days. Different fungi were isolated from cankers, but based on morphological characteristics (pale pink or burgundy colonies), Fusarium spp. were identified in 5.2% of the samples (27/520). Each colony was hyphal-tip purified in a new PDA plate. Macroconidia developed on sporodochia after 30 days of incubation at 25°C on carnation leaf agar. Two morphologically different isolates were analyzed. Colonies of isolate F066 were cottony, dark pink and light pink on the edges when grown on PDA. Macroconidia were hyaline, falcate with rounded apical cells, slightly curved, with 3 to 6 septa (30 to 53 x 5.2 to 6.2 µm). Isolate F094 presented slightly cottony colonies, light pink, and dark pink with pale yellow hues in the central area with macroconidia of similar morphological shape but measuring 36 to 55 x 2.8 to 4.2 µm. In both isolates, chlamydospores and microconidia were absent. The ITS, RPB2, and TEF-1α genomic regions were amplified with primers ITS1/ITS4, 7cf/11ar, and EF1/EF2, respectively (Sandoval-Denis et al., 2018). The ITS (MT640271, PP928999), RPB2 (MT997139, PP934182), and TEF-1α (MT661593, PP934183) sequences were deposited in GenBank, showing 100% similarity with reference sequences of Fusarium culmorum (Wm.G.Sm.) Sacc. and Fusarium avenaceum (Corda) Sacc. for ITS: (MK729631, MT463390), RPB2 (GQ915490, MK185027), and TEF-1α (MN044434, KP400709), respectively. To fulfil Koch's postulates, pathogenicity was evaluated in 8-year-old hazelnut plants cv. Tonda di Giffoni in a commercial orchard. A hole of 6.5 mm in diameter was made in healthy branches using an electric drill and an actively growing mycelial disc (5 mm) was placed into five branches per isolate, ensuring contact of the mycelium with the wood. The wounds were sealed with plastic film to prevent contamination and desiccation. Additionally, PDA discs were inoculated as a control. After seven months, branches were cut longitudinally to verify wood necrosis. Inoculation with isolates F066 and F094 resulted in necrotic lesions ranging between 50-125 mm and 30-80 mm in length, respectively. No necrosis was observed with the control inoculations. Small wood pieces were cut from the advancing necrotic zone, disinfected, and placed on PDA plates and incubated at 25°C as described above. Hyphal tips were taken from mycelia grown from wood pieces and placed on PDA. F. culmorum and F. avenaceum isolates were observed in 100% of the inoculated branches, showing similar mycelial growth and microscopic fungal structures as those observed for the pathogens. To our knowledge, this is the first report of F. culmorum and F. avenaceum affecting hazelnuts plants in Chile and worldwide. Fusarium lateritium had been previously reported in Italy, causing cankers and cambium death in hazelnut twigs (Belisario et al., 2005). The current study reveals a possible host jump and a presumed change in the disease dynamics of these phytopathogens, which primarily cause diseases in cereals (Karlsson et al., 2021).

Hazelnut ( Corylus avellana L.) is a high-value fruit crop in the food industry worldwide. In Chile, more than 36,000 ha are cultivated, mainly for export. However, hazelnut production is globally threatened by Erysiphe corylacearum and Phyllactinia guttata , causal agents of powdery mildew, which compromise photosynthetic efficiency, cause premature defoliation, and can reduce yield. This study aimed to identify the powdery mildew species present in the main hazelnut-growing region of Chile and validate the effectiveness of spore trapping and PCR for early detection of P . guttata . Additionally, during four seasons, the efficacy of several biological and chemical fungicides, alone or in combination, was assessed across three management programs in two commercial orchards in Chile. P . guttata was the only species detected in the 12 sampled orchards. End-point PCR using the Pg2 primer proved specific for P . guttata detection when tested against 13 powdery mildew species and other phytopathogenic fungi commonly found in hazelnut orchards and from spore trapping. Aerial DNA of P . guttata was detectable on spore trap tapes up to 14 days before the appearance of visible signs and prior to fungicide application. Among the tested treatments, sulfur, myclobutanil + kresoxim-methyl, tebuconazole + fluopyram, fluxapyroxad + pyraclostrobin, and penthiopyrad were the most effective treatments. The most effective management program was based on sulfur, fluxapyroxad + pyraclostrobin, and penthiopyrad. Meanwhile, the organic strategy incorporating sulfur, Pseudomonas protegens , and Bacillus subtilis QS713 tended to reduce P. guttata incidence in hazelnut orchards.

Fungal trunk disease (FTD) poses a significant threat to hazelnut (Corylus avellana L.) production worldwide. In Chile, the fungus Diplodia mutila, from the Botryosphaeriaceae family, has been frequently identified causing this disease in the Maule and Ñuble Regions. However, control measures for D. mutila remain limited. This research aimed to evaluate the effectiveness of chemical and biological fungicides against D. mutila under in vitro, controlled pot experiment, and field conditions. An in vitro screening of 30 fungicides was conducted. The effectiveness was assessed by measuring the length of vascular lesions in hazelnut branches inoculated with D. mutila mycelium disks under controlled and field conditions. Field trials were conducted in a hazelnut orchard in Ñiquén, Ñuble Region, Chile. Results showed that three biological and five chemical fungicides were selected in vitro with > 31% inhibition after 14 days. In pot experiments, all fungicides reduced necrotic lesions on branches by 32 to 61%. In field experiments, the most effective systemic fungicides were fluopyram/tebuconazole, fluxapyroxad/pyraclostrobin, and tebuconazole, while the effectiveness of antagonists Pseudomonas protegens ChC7 and Bacillus subtilis QST713 varied with seasonal temperatures. Effective conventional and biological fungicides against D. mutila could be integrated into disease management programs to protect hazelnut wounds from infections.