Biological activity of Pyraclostrobin against Coniella granati causing pomegranate crown rot.

Pomegranate crown rot caused by Coniellagranati is one of the most severe diseases of pomegranate. To date, no fungicides have been registered for controlling this disease in China. Pyraclostrobin, belonging to strobilurin fungicides, has a broad spectrum of activity against many phytopathogens. In this study, based on the mycelial growth and conidial germination inhibition methods, we investigated the biological activity of pyraclostrobin against C. granati at the presence of 50 μg/mL SHAM using 80 isolates collected from different orchards in China during 2012-2018. The EC50 (50% effective concentration) values ranged from 0.040-0.613 μg/mL for mycelial growth and 0.013-0.110 μg/mL for conidium germination, respectively. Treated with pyraclostrobin, the hyphae morphology changed and conidial production of C. granati decreased significantly. The result of transmission electron microscope showed that treatment of pyraclostrobin could make the cell wall thinner, and lead to ruptured cell membrane and formation of intracellular organelle autophagosomes. The pyraclostrobin showed good protective and curative activities against C. granati on detached pomegranate fruits. In field trials, pyraclostrobin showed excellent control efficacy against this disease in which the treatment of 25% pyraclostrobin EC 1000× provided 92.25% and 92.58% control efficacy in 2019 and 2020, respectively, significantly higher than that of other treatments. Therefore, pyraclostrobin could be a candidate fungicide for the control of pomegranate crown rot.