Taxonomic name: Solanum viarum (Dunal)
Common names: juá (Portuguese-Brazil), juá-bravo (Portuguese-Brazil), tropical soda apple (English)
Organism type: shrub
Solanum viarum is an aggressive perennial shrub native to Brazil and Argentina, that has been introduced to other parts of South America, North America, Africa and Asia. The primary means of dispersal seems to be by livestock (cattle) and wildlife, such as raccoons, deer, feral hogs and birds that feed on its fruits. Intra- and inter- county and state movement of livestock that have recently fed on Solanum viarum may be the primary vector for its spread. However, contaminated hay, seeds and bags of manure for composting also serve as a means for its dispersal.
According to Bryson et al. (2002), mature plants of Solanum viarum are 1 - 2m tall and are armed on the leaves, stems, pedicles, petioles and calyxes with broad-based white to yellowish thorn-like prickles up to 1cm long. Leaves and stems are pubescent; flowers are white with five recurved petals and white to cream-coloured stamens. The immature fruits are mottled light and dark green like a watermelon. The mature fruits are smooth, round yellow, and 1 to 3cm in diameter with a leathery skin surrounding a thin-layered, pale green, scented pulp and 180 to 420 flattened, reddish-brown seeds.
agricultural areas, riparian zones, ruderal/disturbed, water courses
According to Mullahey (2003), S. viarum has been observed as a common weed in pastures, ditch banks, citrus groves, sugarcane fields, and wet areas of rangeland. S. viarum is typically found in soils belonging to the order of spodosols (nearly level, somewhat poorly drained sandy soil with a spodic horizon 1 -2m below the soil surface).
Bryson et al. (2002) indicates that S. viarum is a threat to the vegetable crop industry as a competitive weed and because it is an alternate host for numerous pathogens that cause disease in eggplant, peppers, potatoes, tomatoes, etc. These vegetable crop pathogens include the cucumber mosaic virus, gemini virus, potato leafroll virus, potato virus Y, tobacco etch virus, tomato mosaic virus, tomato mottle virus, and the fungal pathogen, Alternaria solani. Mullahey (2003) notes that it is occasionally found growing as a monoculture covering up to 50 acres or more. Bryson et al. (2002) states that damage to croplands, forestlands, and natural habitats and the cost of control of currently infested areas is difficult to determine, but S. viarum has the potential to become a major problem throughout the southern U.S. and could cost farmers and the public billions of dollars annually.
Native range: S. viarum is native to parts of South America.
Known introduced range: S. viarum has become a weed in other areas of South America and in Africa, India, Nepal, the West Indies, Honduras, Mexico, and recently in the U.S. (Bryson et al., 2002).
Introduction pathways to new locations
Agriculture: Contaminated hay, seeds, and bags of manure for composting also serve as a means of its dispersal (Bryson et al., 2002).
Local dispersal methods
Consumption/excretion: According to Bryson et al. (2002), the primary means of dispersal seems to be livestock (cattle) and wildlife, such as raccoons, deer, feral hogs, and birds that feed on fruits. Scarification of seeds by digestive systems of livestock and wildlife seems to promote seed germination.
Preventative measures: In the United States Animal and Plant Health Inspection Service has initiated an education and notification campaign on the potential weed problem of S. viarum. According to Bryson et al. (2002), early detection is paramount to eliminate the threat of this weed, which has the potential to infest millions of acres of pastures, crops, forests, and natural areas in the U.S.
Control: The best means of control varies according to the population size. Individual plants and small populations of S. viarum should be pulled up and burned completely along with all fruit. Larger populations require repeated mowing and/or one or more applications of an effective herbicide. It is important that the plants are not allowed to fruit. Individuals who find S. viarum should contact their appropriate local agency to verify the identity, document the spread, and begin control measures.
According to Mullahey (2003), seedling emergence has been observed to primarily occur during the dry season. New plants will emerge either from seed or from roots of existing plants. Roots have buds that regenerate new shoots.
Reviewed by: Dr. Harold Coble. Crop Science Department, North Carolina State University. USA
Compiled by: National Biological Information Infrastructure (NBII) & IUCN/SSC Invasive Species Specialist Group (ISSG)
Last Modified: Friday, 17 June 2005