| ropical soda apple (TSA) is a troublesome, difficult to control weed in the southeastern United States. Although added to the Federal Noxious Weed Act in 1995, this weed continues to spread from the original core of infestation, peninsular Florida, throughout the United States. Tropical soda apple is now reported as far north as Pennsylvania and as far west as Louisiana. The current regulations devised to prevent the dissemination of this noxious weed have failed, as the hectares infested have increased more than 400% since 1985. Biological and physiological parameters of tropical soda apple were evaluated to aid in designing management strategies. Herbicide susceptibility and required time for TSA to behave as a perennial were investigated in greenhouse studies. Regrowth occurred in 75% of plants ranging from 14 to 55 d of age and occurred as early as one day after emergence. Plants ranging from 1 to 25 d old redifferentiated at a rate of 92% regardless of day after emergence, stem diameter, leaf number, or height. Scanning electron microscopy revealed up to 24 adventitious buds forming in callus tissue on stem apices after cutting. Eight-leaf, 16-leaf, and one-year old TSA plants responded differently to herbicide treatments and rates. Eight-leaf and 16-leaf tropical soda apple were effectively controlled (>90%) with 2,4-D + picloram at 0.44 + 0.11, 0.66 + 0.17, and 0.88 + 0.23 kg ae/ha, 2,4-D + triclopyr at 0.57 + 0.28 and 0.96 + 0.46 kg ae/ha, dicamba, at 0.56 kg ae/ha, picloram at 1.68 and 2.24 kg ae/ha, and triclopyr at 1.12 kg ae/ha or a 2% mixture with diesel fuel. One-year-old plants were effectively controlled with 2,4-D + picloram, 2,4-D + triclopyr, picloram, and triclopyr with water or diesel fuel as the carrier. Brazilian and North American populations of tropical soda apple responded similarly to 1 mM, 0.66 mM, 0.33 mM or no phosphorus for plant height in studies evaluating the effects of phosphorus on development. Phenotypic responses for leaf, bud, and bloom number over 14 weeks illustrated genotypic variation between the two populations. Plants receiving 1 mM of phosphorus produced more fruit than the other treatments. Tropical soda apple at densities of 0, 1, 2, 4, 8, 16, 32, and 64 per 700 cm2 of fescue (Festuca arundinacea Schreb.) resulted in predicted yield losses of 0, 1, 1, 1, 14, 16, 29, and 31% and 0, 1, 1, 1, 1, 11, 19, and 23% respectively for separate experiments. This interference and economic analysis suggests the further spread of TSA should be prevented. To date noxious weed legislation, Federal and State, has been unsuccessful at mandating TSA eradication and dissemination prevention. Tropical soda apple infestations costs U.S. agricultural productionalists... |
