Abstract
In the United Arab Emirates (UAE), royal poinciana (Delonix regia) trees suffer from stem canker disease. Symptoms of stem canker can be characterized by branch and leaf dryness, bark lesions, discoloration of xylem tissues, longitudinal wood necrosis and extensive gumming. General dieback signs were also observed leading to complete defoliation of leaves and ultimately death of trees in advanced stages. The fungus, Neoscytalidium dimidiatum DSM 109897, was consistently recovered from diseased royal poinciana tissues; this was confirmed by the molecular, structural and morphological studies. Phylogenetic analyses of the translation elongation factor 1-a (TEF1-α) of N. dimidiatum from the UAE with reference specimens of Botryosphaeriaceae family validated the identity of the pathogen. To manage the disease, the chemical fungicides, Protifert®, Cidely® Top and Amistrar® Top, significantly inhibited mycelial growth and reduced conidial numbers of N. dimidiatum in laboratory and greenhouse experiments. The described “apple bioassay” is an innovative approach that can be useful when performing fungicide treatment studies. Under field conditions, Cidely® Top proved to be the most effective fungicide against N. dimidiatum among all tested treatments. Our data suggest that the causal agent of stem canker disease on royal poinciana in the UAE is N. dimidiatum.
Highlights
Royal poinciana (Delonix regia (Bojer ex Hook.) Raf.) is a beautiful flowering and shady branching tree
Disease symptoms of stem/branch cankers associated with dieback were observed in the orchard of royal poinciana distributed in Dubai Festival City (DFC), United Arab Emirates (UAE) (Figure 1A)
These signs on royal poinciana are typical of stem canker that is known to be caused by a soil-borne wound pathogen
Summary
Royal poinciana (Delonix regia (Bojer ex Hook.) Raf.) is a beautiful flowering and shady branching tree. This member of the pea family (Fabaceae), which is known as flamboyant, peacock or flame tree, can be recognized by the color of flowering cultivars, ranging from deep red to bright orange or yellow [1]. There is a growing interest in the plantations of royal poinciana in the United Arab Emirates (UAE), mainly in parks, sidewalks, streets, parking lots and open areas. This tree does not often suffer from real problems, stem canker has currently become a serious disease affecting royal poinciana.
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