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Transcript
Stephen H. Brown, Horticulture Agent Lee County Extension, Fort Myers, Florida (239) 533-7513 [email protected] Brown’s Webpage Aaron Palmateer, Plant Pathologist Tropical REC, Homestead, Florida [email protected] Botryosphaeria Dieback of Eugenia, Ligustrum, Oleander, Pittosporum, Viburnum ’Awabuki’ and Wax Myrtle Introduction Eugenia (Syzgium paniculatum), Ligustrum (Ligustrum japonicum) , Oleander (Nerium oleander), Pittosporum (Pittosporum tobira), Viburnum (Viburnum odoratissimum ’Awabuki’) and wax myrtle (Morella cerifera) are six ornamental plants common to South Florida landscapes. Dieback of these plants are sometimes attributed to the fungus Botryosphaeria. Disease symptoms includes yellow, spotted and blighted leaves, dried leaves, defoliations, cankers, tip diebacks, branch diebacks, and often death of the entire plant. Plants in a hedge row are often randomly affected with no discernable pattern. Disease symptoms may be present at any time of the year. Botryosphaeria Genus Botryosphaeria contains fungal plant pathogens that are capable of causing disease that affects a broad host rang of plants. Botryosphaeria is the sexual stage for many species of fungi. Botryosphaeria are often identified by their morphological characteristics. (i.e. the size and shape of their spores). Spore production allows for accurate laboratory identification of Botryosphaeria species. One example, Neofusicoccum parvum was specifically identified as causing dieback of Eugenia. Neofusicoccum parvum is the asexual stage of the fungus that belongs to the Botryosphaeriaceae. The pathogen has been associated with dieback on many other tropical and subtropical hosts, including avocado, citrus, eucalyptus, and mango. Management Recommendations The management recommendations are the same for the related Botryosphaeria pathogens and the diseases they cause in ornamental plants. Good sanitation measures are recommended to manage this disease. It is best to sanitize pruning shears between each plant that has been pruned. There are numerous disinfectants commercially available at home or hardware stores for this purpose. One can also make their own disinfectant solution. Once symptoms (i.e. branch dieback) are present, the affected tissue should be pruned a minimum of 4 inches below the lowest symptomatic branch on the main stem. After pruning, ensure that the exposed vascular tissue of the freshly cut stem is not discolored. If discoloration remains, cut lower on the stem until only healthy tissue remain. Chemical control options are available and should be applied as a preventative. The complex of fungi belonging to the Botryosphaeriaceae usually cause disease when the host plant is under stress such as drought or a nutritional disorder and disease is generally most severe under hot and humid conditions. Consequently, preventative management should begin with fungicide applications in early to mid-spring. Triazoles are products such as Myclobutanil, propiconazole, tebuconazole, or triadimefon. These products provide systemic activity with the ability to get into the plant tissue. Another group of systemic fungicides is the strobilurins, which include azoxystrobin, pyraclostrobin, and trifloxystrobin. Many contact fungicides, which do not have the ability to get into the plant’s vascular tissue, provide cheaper alternatives but are generally applied more often and at higher rates that systemic fungicides. Active ingredients for contact fungicides include captain, Chlorothalonil, copper formulations, and Mancozeb. When using contact fungicides adequate coverage is very important and the product should be applied to freshly cut plant tissue. Eugenia —Early October S.H. Brown Yellowing and spotted leaves S.H. Brown Twig dieback S.H. Brown Plant dieback S.H. Brown Stems with cnacker Eugenia—Early October Moderately affected Most affected Least affected S.H. Brown Various degrees of Botryosphaeria affected plants that were used to conceal an conditioner S.H. Brown Sporadic dieback of plants in a hedge row Ligustrum—Late June S.H. Brown Botryosphaeria sections of this shrub have been removed S.H. Brown Affected leaves S.H. Brown Discolored affected stems Oleander —Early November S.H. Brown Two dead oleander trees are among others of the same species Dried leaves and stems S.H. Brown First signs of cankers that may eventually girdle the tree S.H. Brown Limb dieback Pittosporum—Mid July S.H. Brown Affected hedge midsection S.H. Brown Affected leaves ‘Awabuki’ Viburnum — Late May S.H. Brown Botryosphaeria affected hedge row with “recovering” and defoliated plants S.H. Brown Large canker S.H. Brown Defoliated plants and exposed cankers Wax Myrtle — Late August The removal of infested stems leaves large holes in the canopies of two wax myrtle plants Degrees of stem infections Stem canker The Necessity of Laboratory Analyses Disease symptoms of various fungi are often similar in appearance. A laboratory analysis is often necessary to determine the cause of a plant’s decline and consequently recommended treatment. You may submit plants for analysis to UF Extension Plant Diagnostic Center, 2570 Hull Road, Gainesville, FL 32511. Phone (352) 392-1795, Fax (352) 392-3438. References Harmon, P.F. and Bledsoe, S.D. 2012. Professional Management Guide for Ornamental Plants. #PP202. UF/IFAS, Gainesville, Florida Palmateer, A.J. and Tamowski, T.B., 2011. Branch dieback of Syzgium paniculatum (Eugenia). EDIS #PP283. UF/IFAS, Gainesville, Florida Useful Links Anthracnose Indian Hawthorn Diseases and Disorder Fungicide Survey of Lee County Hibiscus Insect Problems Key Plants / Key Pests Stinkhorns Whitefly (Rugose Spiraling) Florida Native Palms Florida Native Plants Fact Sheets This fact sheet was reviewed by Peggy Cruz, Lee County Extension The Institute of Food and Agricultural Sciences (IFAS) is an Equal Opportunity Institution authorized to provide research, educational information and other services only to individuals and institutions that function with non-discrimination with respect to race, religion, age, disability, sex, sexual orientation, martial status, national origin, political opinions or affiliations. U.S. Department of Agriculture, Cooperative Extension Service, University of Florida, IFAS, Florida A. & M. 1/2013.
