Seasonal susceptibility of sweet cherry pruning wounds to Calosphaeria pulchella, Cytospora sorbicola and Eutypa lata

• Published in: Plant disease
• Main Authors: Li, Sampson, Travadon, Renaud, Trouillas, Florent
• Format: Journal Article
• Language: English
• Published: United States 01.11.2023
• Subjects: Sordariomycetes; climate/weather effects; temporal susceptibility; Prunus avium; wood pathogens; Epidemiology; Subject Areas
• ISSN: 0191-2917
• DOI: 10.1094/PDIS-04-23-0668-RE

Fungal canker pathogens commonly infect trees at pruning wounds leading to branch dieback and loss of productivity in sweet cherry orchards. However, the seasonal susceptibility of sweet cherry pruning wounds to Calosphaeria pulchella, Cytospora sorbicola, and Eutypa lata is not well understood. This study was undertaken to compare the susceptibility of sweet cherry pruning wounds made during the dormant season (January) and the post-harvest season (late-May to June) to infection by main canker pathogens in California. Field trials were conducted in three cherry orchards and trees were pruned at the different periods over two years. Fresh pruning wounds were inoculated with spores of each pathogen, and pathogen recovery was assessed through microbiological isolations at three to four months after inoculations. Pruning wounds made after harvest during late-May and June resulted in significantly higher infection by Cal. pulchella, compared to pruning wounds made during the dormant season in January. Pruning wounds made during both seasons were generally equally susceptible to Cyt. sorbicola and E. lata infections. However, there were one orchard where dormant pruning wounds were more susceptible to infection by E. lata, and one particularly cold winter where Cyt. sorbicola did not infect pruning wounds. Overall, our findings suggest that Cal. pulchella infections of cherry pruning wounds occur most likely during periods of warm temperatures such as late spring and early summer. However, infections by Cyt. sorbicola and E. lata can occur year-around if inoculum is present and if winter temperatures are not abnormally low for California. Finally, our results suggest that the emergence of Cal. pulchella as a major canker pathogen of sweet cherry in California may be the result of a shift from dormant to after-harvest pruning of sweet cherry trees.