Abstract :
Tropical soda apple (Solanum viarum) is a perennial weed that is a serious problem in many perennial grass pastures of Florida and throughout the southeastern United States. Tropical soda apple (TSA) was recently reported in Australia and could possibly be present in other Asian-Pacific Countries. Field and laboratory research in the U.S., primarily in Florida, on the biology, ecology, and control of TSA has resulted in weed management strategies that will benefit Asian-Pacific Countries that are infested with TSA or at risk for invasion by TSA. TSA is unpalatable to livestock and can infest a pasture or native area in 1-2 years resulting in lower stocking rate. At maturity, TSA is from 1 to 2 m tall; stems and leaves have broad-based white to yellowish prickles; the fruit is globular, about 2 to 3 cm in diameter and yellow when mature. Night temperature generally exerted a greater and more consistent effect than day temperature on plant growth and development. In the US, the potential ecological range for plant growth and development is greatest over latitudinal ranges of 15 to 33 degrees S, which is similar to its native South America. Throughout the year, this plant will have immature and mature fruit present that ensures large numbers of viable seeds (@40,000 per plant) with an average germination rate of 70%. Seedling emergence in Florida primarily occurs from August through March compared with April through October for other southern states. Seed in the soil can remain dormant for two or more years though germination will rapidly occur when conditions are favorable. Tropical soda apple has been observed as a weed in agricultural land and in natural areas. The TSA seed is spread by cattle, wildlife, moving water, and anthropogenic activity (contaminated hay, grass seed, shipping cattle, and sod production). Cattle and wildlife spread TSA by consuming the fruit and spreading the seed via feces. Cattle grazing TSA infested areas should be considered a major seed dispersal vector. Tropical soda apple can tolerate a frost or freeze but the foliage will suffer cold damage with some plant mortality. Control strategies include herbicides, biological (insects, viruses), and cultural practices. Successful (90-100%) control has been reported for the herbicide aminopyralid (Milestone), a beetle known as Gratiana boliviana (TSA beetle), and a virus called Tobacco mild green mosaic tobamovirus. An integrated weed control strategy that includes prevention (early detection, rapid response) and control is the best longterm strategy to managing TSA infested areas in the U.S. or Asian-Pacific Countries.
