Tropical Soda Apple

What is tropical soda apple?

Tropical soda apple identification is easiest when the plant is fruiting: its round fruit, mottled green and white like a miniature watermelon before it ripens to yellow, is its most distinctive feature. This prickly perennial in the nightshade family is native to Argentina and Brazil. Ranchers in south Florida first identified it in 1988, likely brought in with contaminated seed, plants or cattle, and it spread quickly through the Southeast and mid-South. It is on the federal noxious weed list.

The problem is mostly economic. Cattle will not eat the prickly foliage, so infested pastures carry fewer animals, and a pasture can be overrun within one to two years. One plant can make 40,000 to 50,000 seeds a year with little dormancy, and germination is high. Cattle and wildlife eat the fruit and spread the seed in their manure. Florida alone has an estimated million acres infested, mostly in improved pastures, and the plant can also form near-impenetrable thickets that crowd native plants out of forest understories.

Tropical Soda Apple identification: what to look for

In warm areas it can carry fruit almost any time, so look for fruit first, then confirm with the prickles and leaves. Wear heavy gloves; the prickles are sharp.

• Growth form: A bushy, upright perennial with several stems, usually 3 to 6 feet tall and about as wide. Stems are hairy; young ones are green and age to brown or coppery.
• Prickles: Straight, broad-based prickles, white to yellowish, cover the stems, the veins of the leaves, the flower stalks and the green cup behind each flower. Most are under half an inch, though some on the branches are longer.
• Leaves: Alternate, 4 to 8 inches long and 2 to 6 inches wide, cut into broad, pointed lobes so they look a bit like oak leaves. Fine hairs give them a soft, velvety sheen; they are dark green above and lighter underneath.
• Flowers: White, five-petaled, about half an inch across, with cream to yellow anthers in the center, in small clusters. In warm areas it can flower nearly all year.
• Fruit: Round berries 1 to 1.5 inches across. Young fruit is green with white mottling or dark veining like a small watermelon; ripe fruit turns yellow. A plant can produce up to about 200 fruits a year.
• Seeds: Each fruit holds 200 to 400 flat, light reddish-brown seeds about a tenth of an inch wide, packed in a sticky coating.

Where it grows in the United States

NC State Extension lists tropical soda apple in Alabama, Arkansas, Arizona, Florida, Georgia, Louisiana, Mississippi, North Carolina, South Carolina, Tennessee and Texas, as well as Puerto Rico. Florida has the most, with roughly a million acres infested. It has been reported throughout Tennessee and in south-central North Carolina, and a Virginia Tech report notes that the USDA PLANTS map has shown a record as far north as Pennsylvania. It is not very cold hardy, but when frost kills the top, the roots resprout, so a hard winter does not end an infestation.

It favors open, sunny, semi-disturbed ground. Look for it in improved pastures (especially bahiagrass in Florida), along ditch banks, in citrus groves, sugarcane and other crop fields, in wet rangeland and in wooded hammocks. In North Carolina it has turned up in fields used to hold cattle. Within a pasture, the thickest stands usually grow where cattle gather to feed and rest. It handles seasonally wet soils, but standing water for more than about three weeks can kill it.

Tropical Soda Apple look-alikes

A few plants get mixed up with it:

• Horsenettle (Solanum carolinense): NC State Extension notes the two are often confused. Horsenettle is a prickly perennial that spreads by rhizomes, with sandpapery, hairy leaves about 2 3/4 to 4 3/4 inches long, usually with 2 or 3 lobes, star-shaped white or purple flowers with a yellow center, and smooth berries that are green when young and turn yellow. Tropical soda apple grows into a shrubby plant 3 to 6 feet tall with bigger, velvety, deeply lobed leaves 4 to 8 inches long, and its young fruit is mottled green and white like a watermelon before ripening yellow.
• Red soda apple (Solanum capsicoides): Also called cockroach berry, this is often mistaken for tropical soda apple, but it is less common and its fruit ripens cherry-red instead of yellow.

How to get rid of tropical soda apple

Pulling, digging and mowing: Mowing will not kill tropical soda apple, but frequent mowing stops it from flowering and setting seed, which is half the battle. Florida's recommended program mows to about a 3-inch stubble as soon as possible and repeats the mowing every 50 to 60 days, as plants reach the flowering stage, through April, then follows with a herbicide on the regrowth. Plants resprout from the roots, so cutting or mowing must be paired with other steps. If you deal with a few plants by hand, wear heavy gloves and long sleeves, and do not leave ripe fruit lying where cattle or wildlife can eat it. After control, replant bare ground with desirable forage quickly and keep checking for new plants.

Cultural control matters most, because the right conditions keep it from coming back.

• Buy cattle from areas free of tropical soda apple, or hold newly bought animals in one pasture or pen for up to six days so any seed they ate passes before they reach clean ground.
• Before shipping cattle out of an infested pasture, mow it to remove the fruit.
• Clean mowers, tractors, trucks and boots before leaving an infested field.
• Scout feeding and resting areas, ditch banks and fence lines often; plants can fruit quickly and at almost any time of year.
• In Florida, a leaf beetle released as a biological control since 2003 weakens plants and cuts fruit production on small or remote patches, but it does not control large infestations and plants often rebound in winter.

Herbicides: For dense infestations in pasture and rangeland, Extension programs rely on aminopyralid, which kills existing plants and also keeps new seedlings from establishing for about six months; some pasture products combine it with 2,4-D. Apply before plants flower whenever possible. Triclopyr is the other main option and is usually used after a mowing program: once the mowed regrowth reaches first flower, typically late May to June in Florida, it is sprayed on the regrowth. Triclopyr has no soil activity, so follow-up spot treatments are needed for seedlings. For scattered plants, spot-spray each one until it is fully covered, add a marker dye so you can see what has been treated, allow a few hours of drying before rain, and recheck monthly. Read the whole label, including any grazing or haying instructions, use only products labeled for your site (pasture, rangeland, crop or noncrop), and remember the label is the law. If you hire someone to spray, make sure they hold your state’s pesticide applicator license; the rules for each state are in our pesticide applicator license guide.

Keeping it from coming back

Most new infestations start with seed carried in by animals or equipment. Cattle, deer, feral hogs, raccoons and birds eat the fruit and pass viable seed, and seed can survive up to six days in a cow's digestive tract. Contaminated hay, sod and machinery also move it. Do not move cattle from infested pastures to clean ones without a holding period, clean equipment and footwear before leaving infested ground, and be choosy about where your hay and sod come from.

Wildlife movement cannot be stopped, so early detection matters. In states where it is new or rare, such as North Carolina and Virginia, Extension asks people to report suspected plants to the state department of agriculture or to EDDMapS, the online invasive species reporting system, so single plants can be removed before they seed.

Questions we get about tropical soda apple

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HorsenettleSolanum carolinenseBuffaloburSolanum rostratumCommon TansyTanacetum vulgare