Tropical soda apple, Solanum viarum Dunal : the plant from hell (Solanaceae) ( Botany circular 27 )


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Tropical soda apple, Solanum viarum Dunal : the plant from hell (Solanaceae) ( Botany circular 27 )
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Coile, Nancy C

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University of Florida
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Botany Circular No. 27
May/June 1993

Fla. Dept. Agric. & Consumer Services
Division of Plant Industry

Tropical Soda Apple, Solanum viarum Dunal: The Plant from Hell 1

Nancy C. Coile 2

INTRODUCTION: Solaoon viarum Donal, tropical soda apple, has recently made its presence known in Florida.
The plant is prickly as are many other Solanum spp., so why would Solanum viarum be called "the plant from hell."
The presence of this weed near Devils Garden, Hendry County, led to this new appellation. Another connection with
hell is the common name "tropical soda apple" which is "Sodom apple" in British-speaking areas. Sodom is the
biblical city noted for its wickedness. Solanum viarum has become the dominant vegetation in vast areas of the
pastures in Glades, Hendry and Highlands counties.

The earliest record in Florida was collected from Glades Co. in 1988 (University of Florida Herbarium
[FLAS]). David W. Hall, who identified the FLAS specimen, believes that Solanum viarum has been present in
Florida since 1981 or 1982 (personal communication). Mullahey (1993) estimated that Solanum viarwn has infested
over 150,000 acres in Florida. The acreage may be higher (Patrick Hogue, Institute of Food and Agricultural
Sciences [IFAS], Extension-Agent Highlands Co., personal communication).

Figures 1-3. Solanm viarum Dunal. ig. 1) Tropical soda apple; 2) Flowers; 3) Immature to mature fruit (Photography credit:
Jeffrey W. Lotz).

Contribution No 27, Bureau of Entomology, Nematology and Plant Pathology Botany Section.
2 Botanist, Division of Plant Indusuy, P. O. Box 147100. Gaineville, FL 32614-7100.

How has this species, which is native to Brazil and Argentina, become a problem in Florida so rapidly? There are
about 413 seeds per fuit and 125 berries per plant with germination exceeding 75% (Mullahey 1993). Although cattle avoid
eating the prickly vegetation, their long tongues can reach into the foliage to pluck off the fruits. Cattle are apparently good
vectors for spreading the seed through defecation. Solanum viarum is also present in hammocks where cattle retreat to rest.
It occurs in ditch banks, citrus groves, sugar cane fields, watermelon fields and along roadsides.Wildlife, such as raccoons,
deer and feral pigs, apparently also spread the seed. Birds have not yet been observed feeding on the fruits and may not be
vectors for spread.

DISTRIBUTION: Originally native to Argentina and Brazil, Solanum viarum has spread into other parts of South America,
Africa, India, Nepal, Caribbean, Mexico and Florida. It is thought that most Florida counties south of Lake County have been
infested by this pest plant Herbarium specimens at Division of Plant Industry Herbarium (PIHG) document Solanum
viarum in Osceola (W. J. Shirle B93-172), Polk (J. E. Lindsav B93-180\, Hendry (Coile 5936. 59371, Highlands (CoQji
5938.5939 and Alachua (Coile 5947) counties. The latter county is north of Lake Co.

DESCRIPTION: Solanum viarum is an herbaceous perennial which can persist if winters are mild. Plants grown in good
conditions may reach 2 m (6 feet) in height; usually the plants are about 1 m (3 feet) tall. The stems are sturdy and have
scattered small, hooked prickles. Leaves are alternate, simple, lobed; to 20 cm (8 inches) long, to 15 cm (6 inches) wide;
and covered with fine soft hairs which give a velvety sheen to the leaves (Fig. 1). Rigid, yellowish prickles up to 20 mm (%
inch) are scattered along the midvein and the secondary veins on both surfaces of the leaf blade and are more concentrated
on the petiole (leaf stalk). The flowers are in small terminal clusters. The calyx is five-lobed and has tiny prickles on the
surface; corollas are white, with five, recurved petals; anthers are cream-colored and surround the single pistil (Fig. 2).
Immature fruits are pale-green with dark-green veining (appear like a tiny striped watermelon). Mature fruits are a dull
medium-yellow, leathery-skinned, about 2 to 3 cm (up to 1 A inches) across (Fig. 3). The pulp band is narrow, pale-green,
mucilaginous and scented. Seeds are numerous, flat, bitter and mucilaginous.

MAY BE CONFUSED WITH: World-wide there are over 1400 species of Solanum (Mabberly 1987). In Florida, the
prickly species are: S. capsicoides Allioni, S. carolinense L., S. dimidiatum Raf., S. tempacense Dunal, S. rostratum Dunal,
S. sisymbriifolium Lam., S. torvum Sw. and S. viarum Dunal.

Solanum capsicoides may be listed as S. aculeatissimum Jacq. or as S. ciliatum Lam. in older references
(Kartesz and Kartesz 1980). Common names are soda apple, cockroach berry, Devil's apple, love-apple and berenjena
(Perkins and Payne 1978; Standley 1923). The distribution is Texas, southern U.S., Bermuda, West Indies and tropical
America (Correll and Johnston 1970). The stems are densely covered with broad-based, hooked, yellowish prickles, in
contrast to S. viarum which has scattered prickles. The fruits are persimmon-red while S. viarum has yellow fruits which
are slightly larger. Solanum capsicoides may grow in the same pastures as S. viarum, but in comparatively small numbers.

Solanum caroinense, or horse-nettle, was originally native to the southeastern United States north to Virginia
and Kentucky. It is now distributed north to Ontario and westward (Gleason and Croquist 1991). This weed of disturbed
areas has lavender to white flowers about 2 cm (% inch) wide. The prickles are not as long as those ofS. viarum. Plants
may reach 1 m (3 feet) in height, but are usually much shorter.

Solanum dimidiatum, originally of Kansas, Arkansas and Texas (Gleason and Cronquist 1991), has now
spread to south Georgia and North Florida (Clewell 1985; Small 1933; Wunderlin 1982). Commonly called western horse-
nettle, this species is distinguished by its purple corolla with a green eye. The fruit is pale yellow and the plant is clothed
with stellate hairs (Correll and Johnston 1970).

Solanum tampicense (called S. houstonii in the earlier edition of this circular) is a newly discovered pest plant
in Florida. Wunderlin et al. (1993) note that S. houstonii Dunal is a homonym of the 1807 S. houstonii Martyn and is thus
illegitimate. The common names for this species are Tampico soda apple and wetlands soda apple. Standley (1923) uses
the following common names: aijicon, huistomate, or huevo de gato. Solanum tampicense is distributed from Mexico, West
Indies, British Honduras (Gentry and Standley 1974) and now Florida. The leaves of S. tampicense differ markedly from
S. viarum: (1) being more elongate (to 16 cm long) and narrower (2.2 to 5.5 cm) wide; (2) lacking straight prickles but
having curved on both leaves and stems. The plants are straggly and clamber onto other plants. Mark L. Runnals (personal

communication) observed that plants along the Peace River (near Arcadia) attained a height of 15 feet. The fruits are
arranged in lateral clusters opposite the leaves, small (to 8.5 mm across), and red. The sites observed in Florida are along
rivers and in cypress stands. The presence of this alien species may imperil natural areas of the state.

Solaium rostratum, with common names of buffalo bur, Kansas thistle and mala mujer (Correll and Johnston)
1970 is native to the great plains (Gleason and Cronquist 1991) and is an occasional weed in Florida. It is not likely to be
confused with S. viarum because the leaves resemble a watermelon leaf (are pinnatifid) and are covered with stellate hairs
and many straight prickles. The extremely prickly calyx covers the fruits entirely.

Solanum sisymbriifolium, introduced from South America (Clewell 1985), occurs in the Panhandle and
Central Florida Unlike S. viaman, it has pinnatifid leaves. There are glandular hairs on the leaves which give it the common
name, sticky nightshade. The spiny calyx mostly cover the red berry; spines are not as dense as those ofS. rostratum.

Solanum torvum is a federally-listed noxious weed. Common names are bushy white solanum (Correll and
Correll 1982) and susumber (Bird and Heinlein, no date; Gentry and Standley 1974). Leaf shape is highly variable: leaves
may be lobed similar to those of S. viarum, unlobed, or oddly lobed. Both stems and leaves are covered with stellate hairs,
and there may also be prickles which are straight or curved. The flowers are terminal and the petals are not recurved. Ripe
fruits are yellow. Specimens, which were grown for especially for their edible fruit, have been located in Florida.

ECONOMIC IMPORTANCE: The difficulty of control is due to its: (1) prickly nature, (2) rapidly expanding range, and
(3) tendency to form huge patches. This suggests that S. viarum will have a major economic impact in agricultural fields,
orange groves and pastures. Natural areas are also at risk Because of the displacement of native and preferred forage plants
and the components of natural ecosystems, the Florida Department of Agriculture and Consumer Services in 1993 listed S.
viarum as a noxious weed, followed in 1994 by addition to the Federal Noxious Weed List (USDA).

Solanum viarum is grown in India as a source of steroids (Mullahey 1993). The glycoalkaloid solasodine which
is present in the fruit is a precursor for the steroid diosgenin, which is used in contraceptives (Budavari 1989). Although
it is not advised, I bit into a fruit as far as the seed cavity and immediately took the fruit out of my mouth. It is bitter and the
mucilage sticks to the teeth. The bitter alkaloids of the solanine type (eg., solasodine) are poisonous to humans (Kingsberry
1964; Smith, 1976).

CONTROL MEASURES: Research is underway at the IFAS Southwest Florida Research and Education Center toward
controlling this pest plant. Moderate success in control has been observed by mowing the plants before they set fruit and
following up with the application of an herbicide to the young seedlings. Reintroduction of seed from neighboring
uncontrolled sites will require repeating control measures. Considerably more funds and research need to be directed
towards understanding how to control this extremely pestiferous "plant from hell."


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Revised August 1996