Biological and chemical fungicide programs supported by spore trapping and PCR-based detection for controlling...

Hazelnut (Corylus avellana L.) is a high-value fruit crop in the food industry worldwide. In Chile, more than 36,000 hectares 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 combinations, was assessed across three management programs in two commercial orchards in Chile. Phyllactinia guttata was the only species detected in the twelve 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.