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Plant Pathology Circular No.150,
January 1975
Fla. Dept. Agric. & Consumer Services
Division of Plant Industry
W. H. Ridings and R. B. Marlatt(1)
Bottlebrush (Callistemon spp.) is a popular small evergreen ornamental tree grown primarily in central Florida and southward (1,4). Its colorful bottlebrush-like flowers and easy maintenance make this a very suitable landscape plant.
SYMPTOMS. Stem galls caused by the fungus Sphaeropsis tumefaciens Hedges (5) vary in size from small stem swellings to baseball-sized enlargements (fig. 1). Frequently, large galls are associated with multiple stem branches, a condition known as witches' broom. The fungus appears to infect the stems of bottlebrush more easily through wounds (7).
Stem galls are found on established plantings and occasionally in the commercial nursery. These galls are debilitating to the tree as well as unsightly.
Figure 1. (85K) Sphaeropsis galling of bottlebrush: A) tree showing extensive galling; B) small developing galls on branches; C) large gall showing witches' broom effect.
(1) Plant Pathologist, University of Florida, Agr. Res. & Educ. Center, Homestead FL 33030.
HOST RANGE. Galls, caused by S. tumefaciens, have been reported on Citrus spp. primarily in Jamaica (1,6). In Florida, citrus is apparently attacked infrequently (1,3). This fungus has been associated also with galls on Carissa spp., Nerium oleander L., Ilex opaca Ait., Schinus terebinthifolius Raddi., and Eucalyptus cinerea F. Muell. ex. Benth. (2).
CONTROL. Prune out branches well below gall areas and destroy infected branches. Pruning tools should be dipped in a disinfestant such as 10% Clorox before each cut. Pruning wounds on the branches should be treated with protective paint. Information on control with chemicals:
Reference to University of Florida/IFAS Pest Control Guides
Contribution No. 392, Bureau of Plant Pathology, P.O. Box 1269, Gainesville, FL 32602.
References
1. Blazquez, C. H., A. G. Naylor, and D. Hastings. 1966. Sphaeropsis knot of lime. Proc. Fla. State Hort. Soc. 79:344-350.
2. Bureau of Plant Pathology (Plant Disease Records), Division of Plant Industry, Fla. Dept. of Agr. and Consumer Serv., Gainesville. (Unpublished)
3. Burnett, H. C. 1971. Sphaeropsis knot of citrus in Florida. Fla. Dept. Agr. and Consumer Serv., Plant Pathol. Circ. No. 106. 2 p.
4. Bush, C. S. 1969. Flowers, shrubs, and trees for Florida homes. Fla. Dept. Agr. and Consumer Serv. Bull. 195. 179 p.
5. Hedges, F. 1911. Sphaeropsis tumefaciens, nov. sp., the cause of the lime and orange knot. Phytopathology 1:63-65.
6. Holliday P., and E. Punithalingam. 1970. Sphaeropsis tumefaciens. Descriptions of pathogenic fungi and bacteria No. 278. Commonw. Mycol. Inst., Kew, Surrey, England. 2 p.
7. Marlatt, R. B., and W. H. Ridings. 1974. Sphaeropsis gall of bottlebrush tree, Callistemon viminalis, a new host. Phytopathology 64(7):1001-1003.
