Date of this Version
Agricultural Research January 2002
Small victories are being reported by the Agricultural Research Service (ARS) in the war against tropical soda apple (Solanum viarum), a nonnative, invasive weed of pastures, row crops, forests, and urban areas throughout the southeastern United States.
Tropical soda apple (TSA) was first observed in Florida in 1988, causing little concern with fewer than 2,000 acres affected. Just 6 years later, however, researchers estimated that more than 1 million acres were infested. Charles T. Bryson, an ARS research botanist with the Southern Weed Science Research Unit in Stoneville, Mississippi, says researchers believe the resilient weed has now been eradicated from Louisiana, Tennessee, and Pennsylvania, but efforts must not become lax.
A recent report from the Stoneville unit shows that “a combination of late summer mowing, fall herbicide application, and normal winter conditions can prevent TSA survival.” Although the plant is known to overwinter as far north as 35 degrees latitude, Bryson says early detection and other control methods by persistent cattle ranchers in several states have prevented cattle from spreading the weed northward. He says Florida cattle ranchers were aided by recent severe winters and drought.
The Cattle Connection
Cattle cannot resist the sweet smell of TSA’s golf-ball-sized, yellow fruit, Bryson says. “Cows will reach into the prickly plant with their long tongue and snatch the mature fruit off without getting injured,” he says.
When cattle are moved to neighboring states for winter feeding, they transport ingested seeds with them. The seeds are also spread by way of composted manure, grass seed, sod, or hay, as well as by deer and other wildlife. TSA infests pastureland by outcompeting forage grasses, and the prickly foliage drives cows from shaded areas, leading to heat stress. Losses to Florida cattle ranchers are estimated to be about $11 million annually.