Investigators bide their time to catch invasive weeds

Winter weather has covered the tracks of a pair of plant pests that invaded South Carolina last fall, but Clemson University investigators will be waiting for them when they emerge in the spring.

“In the winter as plants die back it’s impossible to identify them,” said Christel Harden, who leads the plant pest detection and nursery inspection efforts for Clemson’s Department of Plant Industry. “Once these invasive plants begin to grow again, we’ll be better able to determine the extent of their spread and try to eradicate them.”

The pair of pests appeared in the Palmetto State shortly before going dormant for the winter. Both present potential problems for important agricultural crops and are regulated by state and federal governments as noxious weeds.

The debut of Benghal dayflower, first reported by Lowcountry botanist and nurseryman Daniel Payne, led Department of Plant Industry investigators to conduct a house-to-house survey for the weed in November, concentrating on waterfront neighborhoods where the weed first appeared.

News reports on the weed’s discovery prompted homeowners to report two other infestations, since confirmed in St. Matthews and near Rowesville in Orangebug County.

Benghal dayflower — which bears the alias “tropical spiderwort” and an official name of Commelina benghalensis — grows a dense stand that can smother other plants. It is a particularly damaging pest to row crops like soybeans, peanuts and corn, which combined generate about $500 million in farm receipts in South Carolina, according to the National Agricultural Statistics Service.

Harden said the department is still investigating how the weed found its way to the Palmetto State — possibly among container plants or seeds carried by birds. This is the first time the weed has been found in the state outside of a plant nursery. Regulators in 2005 found Benghal dayflower in a container with a liriope at a South Carolina nursery, where it was destroyed.

Itchgrass, a tall Asian grass that lives up to its name, was identified in Moncks Corner in October, the first documented South Carolina detection of the pest. A second suspected case since has been reported in Spartanburg County.

“The diverse locations could indicate that it was a hitchhiker,” Harden said. “Itchgrass seeds often attach to road-construction equipment and farm machinery, depositing themselves along highways and railroads.”

The thick, fast-growing grass, which can grow 10 feet tall if left unchecked, chokes out native species. Thought to have made its way to the United States on railroad cars from Latin America, it now infests the Gulf Coast states.

“At first glance it looks very much like Johnson grass, but there are sharp, irritating hairs along its spine,” Harden said. “It will show itself again in the spring and we’ll know the extent of the infestation. Then we’ll determine how best to manage it.”

The Department of Plant Industry conducts certification and inspection programs related to plant nurseries and enforces state laws and regulations that protect the state from exotic and invasive species.

It is part of Clemson’s Regulatory Services branch, which includes departments that regulate pesticides and structural pest control, verify that fertilizer and lime meet standards and labeled guarantees, conduct seed and organic certification programs, diagnose plant pests and ensure readiness to respond to catastrophic events that impact the state’s agriculture.

Courtesy Clemson