Strategies to address emerging fungal diseases in peony (Paeonia lactiflora) in the United States

Abstract

The most important step in any effective disease management strategy is proper diagnosis. Therefore, in an effort to assist growers with disease management, herbaceous peony (Paeonia lactiflora) samples were collected and submitted to our lab from 12 states in the United States to determine the range of diseases present in both landscape and commercial settings. Both morphological and molecular techniques were used in the identification of pathogens isolated from peony flowers, leaves, stems, and roots. Trials were conducted to confirm the ability of all pathogens to cause disease on healthy peony tissue. This survey revealed new species-host-state combinations in several states as well as five different fungal genera that had not previously been identified on peonies in the country: a Botryosphaeria sp., up to 3 Colletotrichum spp., Mycocentrospora acerina, a Phoma sp., and Pilidium concavum. Each of these pathogens have only been reported a few times worldwide and there is correspondingly little to no information available on their management. Given the need for growers to address these emerging disease issues, we outline potential management strategies for fungal peony pathogens. Our recommendations take into account general fungal disease management tools, published information on the specific biology of these organisms, observations of peony diseases over our years of fieldwork, and examples from other pathosystems that have been successful in managing diseases caused by the pathogens we have found on peonies.