Forest Health > Insects and Diseases publication
Diseases of... Hardwood Root
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MIMOSA WILT
Typical symptoms and decline for mimosa trees infected with the vascular wilt pathogen, Fusarium oxysporum f. sp. perniciosum.
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| Pathogens: |
Fungus Fusarium oxysporum f. sp. perniciosum |
| Common Host: |
Mimosa Albizia julibrissin |
Significance: |
Mimosa wilt has not been extensively evaluated in Florida. It is known to occur in parts of the state, however, and it is usually very damaging or lethal to its victims. The frequent use of the graceful and seasonally showy mimosa as an ornamental tree could render this disease more important in the future. Mimosa wilt is an excellent example of a group of diseases referred to as vascular wilts which includes, among others, the well known dutch elm disease currently causing so much damage to elms across the United States and Canada. |
Recognition: |
The first expression of symptoms by trees infected with the mimosa wilt fungus is a conspicuous paling and drooping of leaves, initially appearing on a single branch. As the disease progresses, drooping leaves turn yellow, dry out, and fall from the tree. In time, this process repeats itself throughout the crowns of infected trees, and death of the trees may result within a year of the time symptoms are first observed.
In many cases, root systems are not rapidly killed, and suckers (sprout-like growths) are produced repeatedly for several years from root collars at the base of disease-killed trunks. Some bark fissuring or splitting, accompanied by varying degrees of bleeding or exudation and sometimes gummosis (the oozing of gummy or rubbery excretions along the bark) may appear on infected trunks and major branches.
Internally, the wood of infected branches and stems usually exhibits a characteristic brownish discoloration, typically in the outermost layers of the sapwood. This vascular streaking may encompass the entire circumference or only portions of infected tree parts. |
Infection Biology: |
Mimosa wilt infections arise as a result of direct penetration of roots by the fungus pathogen. Once inside the host root, the pathogen grows into roots of ever increasing size, ultimately into the tap root, and from there into the stem and branches of the tree. This progressive development of the pathogen occurs in the vascular tissues of the host resulting in the death and/or blockage of the critical, water conducting cells. As a result, the tree wilts and eventually dies.
Unlike certain other vascular wilt diseases such as Dutch elm disease, mimosa wilt has no known insect vector (an insect that carries the pathogen from tree to tree, often introducing it into a healthy tree). The pathogen can be spread in infested soil or through moving infected wood or seedlings from place to place. Local spread of the mimosa wilt fungus is accomplished through the root-to-root growth of the pathogen.
Although root wounds are not necessary for infection, it is presumed that wounds might aid the pathogen's entry. Root damage caused by certain nematodes has been shown to increase the severity of mimosa wilt infections. |
Control: |
No proven treatment for infected trees is known. Preventive measures include avoiding the movement of infested soils or infected seedlings or trees. Treat soils with an appropriate biocide (methyl bromide, etc.) before planting mimosa in areas of known parasitic nematode populations or previous history of mimosa wilt. Don't prune infected trees and then healthy trees without first sterilizing pruning shears, saws, etc. Utilize resistant mimosa varieties when planting ornamentals, if available |
Bulletin No. 196-A | Printed October, 1983 | Contact the Forest Health Section |
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