Identification of the Causal Agent of Leaf and Crown Rot of Liriope in Louisiana

Publication Year:
2015
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Repository URL:
https://digitalcommons.lsu.edu/gradschool_theses/70
Author(s):
Proano, Carla Milena
Tags:
leaf and crown rot; Liriope; disease incidence; Fusarium oxysporum; Phytophthora palmivora
thesis / dissertation description
Leaf and crown rot of Liriope is an increasing problem affecting Liriope in the nursery and landscape for the past eight years primarily in the southeastern United States. Symptoms start with water soaking of leaves at the crown area, followed by yellowing of the entire leaf starting at the base. Affected crowns rot and leaves turn brown leading to death of the plants. Phytophthora palmivora and Fusarium oxysporum were isolated and identified from ‘Big Blue’ Liriope symptomatic plants taken from the nursery and landscape. The pathogens were positively identified by morphological features of the pathogens and then confirmed with polymerase chain reaction. Pathogenicity tests were performed in the greenhouse using three Liriope cultivars including ‘Emerald Goddess’ and ‘Super Blue’, considered to be tolerant to this disease, and ‘Big Blue’ which was considered to be more susceptible. Four inoculation treatments were used: water control, Phytophthora palmivora, Fusarium oxysporum and P. palmivora + F. oxysporum. Results from this study confirm the pathogenicity of previously identified P. palmivora and F. oxysporum microorganisms causing leaf and crown rot. P. palmivora was the primary microorganism causing leaf and crown rot on ‘Emerald Goddess’ and F. oxysporum on ‘Big Blue’ leading to increased disease incidence and a decrease in fresh and dry weight of leaves. ‘Super Blue’ showed no significant differences in fresh and dry weight of leaves and roots, and in percentage of disease incidence between the inoculation treatments (P>0.05). A survey was conducted at 11 wholesale and 7 retail nurseries in Louisiana to confirm that leaf and crown rot was a problem in Liriope production. P. palmivora and F. oxysporum were recovered from plants exhibiting leaf and crown rot symptoms which indicated that the disease was present in all nurseries. Poor sanitation and cultural practices were found to be the primary factors leading to the development and spread of leaf and crown rot disease.