Miller, James H.; Manning, Steven T.; Enloe, Stephen F. 2010. A management guide for invasive plants in southern forests. Gen. Tech. Rep. SRS–131. Asheville, NC: U.S. Department of Agriculture Forest Service, Southern Research Station. 120 p.
Tropical soda apple (Solanum viarum Dunal) is an upright, thorny perennial subshrub or shrub, 3 to 6 feet (1 to 2 m) in height, characterized by remaining green year-round in most southern locations. It has oak-shaped leaves, clusters of tiny white flowers, and golf-ball sized fruit that are mottled green white turning to yellow in late summer to fall. Immature greenish fruit can contain viable seeds. Fruit have a sweet smell attractive to livestock and wildlife. Spread is now rapid by cattle and other livestock transportation that have consumed the fruit and by wildlife-dispersed seeds as well as seedcontaminated hay, sod, and machinery. Report infestations to county agents for treatment under a federally sponsored eradication program. One leaf feeding biocontrol insect has been released in Florida, Georgia, Alabama, and Texas, and has become established in Florida. Three more biocontrol insects are undergoing further testing and are expected to be released soon. Herbicide treatments should not be applied if heavy defoliation is observed.
Management strategies
- Do not allow cattle to eat fruit.
- Treat when new plants are young to prevent seed formation.
- Cut and mow when fruit are not present (cutting and mowing is used for stopping fruit production but will not control plants).
- Collect and destroy all fruit.
- Manual pulling is hindered by thorny branches and limited to new seedlings.
Recommended control procedures for isolated sightings
- Thoroughly wet leaves and stems with one of the following herbicides in water with a surfactant at times of flowering before fruit appear: Garlon 4 (or Remedy® in pastures), Tordon K* ‡, or Arsenal AC* as a 2-percent solution (8 ounces per 3-gallon mix); Milestone VM* as a 0.5-percent solution (2 ounces per 3-gallon mix); Tordon 101* ‡ as a 4-percent solution (1 pint per 3-gallon mix); or a glyphosate herbicide as a 3-percent solution in water (12 ounces per 3-gallon mix).
- If mowing is used to stop fruit production, delay herbicide applications until 50 to 60 days to ensure adequate regrowth.
* Nontarget plants may be killed or injured by root uptake.
‡ When using Tordon herbicides, rainfall must occur within 6 days after application for needed soil activation. Tordon herbicides are restricted use pesticides.
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