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Copyright 2005, Board of Trustees, University
Fort Pierce ARC Research Report RL-1974-4
DISEASES OF STYLOSANTHESi:SPP,' i //DV -
R. M. Sonodal
DEC 9 1977
The intensive use of legumes for forage in tropical and sub-tropcal
regions is of recent origin (8). The genus Stylosanthes, indigenous trom
lowlands to about 2000 meters in both tropical andrtempyerate regions (lO,
Kretschmer, personal communication, 1974) has become an importaht-:legume
for forage in Australia (8) and is also being grown or tested for this
purpose in South and Central America, east Africa, the Phillippines, south-
east Asia and Florida. So far only a few diseases have been reported on
this genus. With more intensive and extensive use of the genus, however, the
potential for losses to diseases is increased. The following is a literature
review and notes on diseases of the genus at the Agricultural Research Center,
Fort Pierce (ARC-FP).
FOLIAGE AND STEM DISEASES -- Several fungi classified as Cercospora spp. have
been reported as pathogens of Stylosanthes spp. The first reported was C.
stylosanthes Spegazzini reported by Spegazzini in 1883 from Paraguay (6).
Chupp (6) doubted the validity of including this fungus in the genus
Cercospora. C. commonsii Sacc. (C. stylosanthes Ellis & Ev.) was reported on
S. eliator Swartz. (S. biflora Britton) from several collections made in
Delaware (6). AbdouL'(1) reported that a Stylosanthes sp. was moderately
susceptible to C. arachidicola Hori in inoculation tests. Cooper (quoted by
Abdou (1) ) found a Stylosanthes collection that was susceptible to C.
personata (B. & C.) Ell. & Ev. Cercospora canescens Ellis & Martin has been
reported on S. guyanensis in Malawi (14). No Cercospora have been found on
Stylosanthes at the ARC-FP.
Colletotrichum leaf spot and stem canker incited by Colletotrichum
gloeosporioides Penz. has caused severe damage to some lines of Stylosanthes
being tested at the ARC-FP (9, 12, 13). A similar disease has been reported
from parts of South and Central America (13) and recently from Australia
(Pitkethley, personal communication, 1974). At the ARC-FP, lesions on tri-
foliate leaves were 1 to 2 mm in diameter, almost white in the center and
surrounded by a dark margin. Stem lesions were elliptical, 2 to 4 mm in
length and similar in color to leaf lesions. Severely infected leaves
yellowed and abscissed. Death of some plants followed severe infection. In
laboratory and field tests at the ARC-FP no cultivar was found immune to the
disease; however, there were great differences in tolerance to the disease
among cultivars. Grof (personal communication, 1972) reported differences
in tolerance in his lines of Stylosanthes to three isolates of the fungus in
Curvularia sp. has been isolated from a common leafspot found on both
native and introduced Stylosanthes spp. in Florida. The leafspots were
1/ Assistant Plant Pathologist, University of Florida, Institute of Food and
Agricultural Sciences, Agricultural Research Center, Fort Pierce.
similar to that caused by C. gloeosporioides except the center of the lesions
were a tan color instead of near-white. The disease appears to have very
little effect on the plants.
Phoma sp. causing a black spotting on stems and leaves has been found in
Rhodesia (Clatworthy, personal communication, 1973).
SOIL-BORNE DISEASES -- Rhizoctonia solani Kuhn is reported to cause a stem rot
on S. guyanensis guianensiss) (Aubl.) Sw. in Zambia (4). At the ARC-FP stem-
killing of prostrate growing S. humilis H.B.K. by R. solani was found in the
fall of 1973. Infection occurred where stems were in contact with soil. In
some. cases-entire plants were killed.
A black root rot of S. guyanensis incited by Corticium invisum was
reported from India (11).- Pythium aphanidermatum (Edson) Fitz. killed trans-
plants of several lines of S. humilis during warm wet weather in the fall at
the ARC-FP. A plant killed by Sclerotium rolfsii Sacc., an omnivorous patho-
gen, was found in the spring of 1974 at the ARC-FP.
Bacterial and Virus Diseases
Pseudomonas solanacearum E. Smith was reported on S. humilis in the
NorthernTerritory (3). Three virus diseases have been reported, a mild
mottle on S. humilis from Kenya (5) Groundnut Rosette virus on Stylosanthes
spp. from Malawi (2) and Legume 'little leaf' on S. gracilis HBK (S.
guyanensis) from Australia (7). No virus or bacterial disease of Stylosanthes
has been identified at the ARC-FP.
In the summer of 1972, severe lesions were noticed on S. guyanensis at
the ARC-FP. Leaf-tip die-back and scattered necrotic lesions reminiscent of
bacterial or fungal invasion were found on the leaves. The leaves abscissed.
The onset of necrotic lesions was usually preceded by heavy rains. No
pathogens were isolated from the lesions.- Remission of the condition followed
applications of muriate of potash (J. B. Brolmann, personal communication,
The number of diseases reported on the genus Stylosanthes and the
amount of information with regard to these diseases is currently small. Of
these diseases only that caused by C. gloeosporioides has exhibited potential
for significant losses if susceptible varieties are planted.
Studies should be conducted to determine the consequences of planting
in previously cropped areas harboring the omnivorous pathogens, P. aphanider-
matum, S. rolfsii and R. solani, common pathogens on vegetables. Pastures
following vegetable crops is a common sequence on farms near the ARC-FP.
Care should be taken in the selection and breeding of members of this
genus as with any other crop plant to make certain that cultivars highly
susceptible to disease are not released for commercial use.
Appreciation is expressed to G. T. Kovalik, Hume Library, University
of Florida, and D. H. Smith, Plant Disease Research Station at Yoakum,
Texas A & M University, for their help with the literature survey.
1. Abdou, Y. A.-M. 1966. The source and nature of resistance in Archis L.
species to Mycosphaerella arachidicola Jenk. and Mycosphaerella
Berkeleyii Jenk., and factors influencing sporulation of these fungi.
Ph. D. Thesis. North Carolina State of the University of North
2. Adams, A. N. 1967. The vectors and alternative hosts of Groundnut
rosette virus in Central Province, Malawi. Rhodesia Zamb. Malawi
J. Agric. Res. 5:145-151. (Abst. in Rev. Appl. Mycol. 1968 vol. 47
3. Aldrick, S. J. 1971. Bacterial Wilt (Pseudemonas solanacearum) of
Stylosanthes humilis in the Northern Territory. Tropical Grasslands
4. Anon. 1966. Rep. Res. Brch. Minist. Agric. Zambia 1966. P.34-46.
(Abst. in Rev. Appl. Mycol. 1969 vol. 48, p. 610).
5. Anon. 1970. Annual Report East African Agriculture and Forestry
Research Organization. 1969. 179 pp. (Abst. in Rev. Plant Path-
ology. 1971. vol. 50, p. 485).
6. Chupp, C. 1953. A monograph of the fungus genus Cercospora. Published
by the author, Ithaca, N.Y. 667 pp.
7. Hutton, E. H. and N. E. Grylls. 1956. Legume 'little leaf', a virus
disease of subtropical pasture species. Aust. J. Agric. Res. 7:
8. Hutton, E. M. 1970. Tropical Pastures. In Advances in Agronomy Vol. 22
(ed.) N. C. Brady. Academic Press, New York and London. pp. 1-73.
9. Kretschmer, A. E., Jr., R. M. Sonoda, and J. B. Brolmann. 1974.
Morphologic and disease susceptibility differences among Stylosanthes
humilis introductions and selections in south Florida. Soil and
Crop Science Soc. Fla. Proc. 34: (In Press).
10. Mohlenbrock, R. H. 1957. A revision of the genus Stylosanthes Ann.
Mo. Bot. Gdn. 44:299-355.
11. Sarmah, K. C. 1956. A note on the use of Stylosanthes guyanensis Sw.
var. gracilis (H.B.K). Vog. in relation to black rot disease of
tea. Two & a Bud (News Lett. Tocklai Exp. Sta.) 3:31. (Abst. Rev.
Appl. Mycol. 1957. vol. 36 p. 557).
12. Sonoda, R. M. 1973. Incidence of Colletotrichum leaf spot and stem
canker on introductions and selections of Stylosanthes humilis.
Plant Dis. Reptr. 57:747-749.
13. Sonoda, R. M., A. E. Kretschmer, Jr., and J. B. Brolmann. 1974.
Colletotrichum leaf spot and stem canker on Stylosanthes spp. in
Florida. Tropical Agric. (Trinidad). 51:75-79.
14. Thomas, D. 1973. Nitrogen from tropical pasture leagues on the African
continent. Herbage abstracts: 43:33-39.