South Carolina farms can no longer ship sweet potatoes or seeds to two other states after a non-native pest was discovered in a Darlington County field.
Clemson University’s Department of Plant Industry (DPI) said it first encountered the Guava root-knot nematode while searching for another invasive pest in 2017, but new research suggests the pest is more destructive than first believed.
“The nematode becomes a problem in large numbers, because there aren’t any natural predators,” assistant director for plant protection Steven Long said. “So you’ll see populations explode and the sheer numbers are what cause the problem.”
That has led Louisiana and Mississippi to begin quarantines on fresh market sweet potatoes, seeds and slips. While Mississippi only blocked shipments from Darlington County, Louisiana applied the ban statewide. The two states also bar potatoes from Florida and North Carolina.
However, Louisiana’s ban covers more than the sweet potato itself. The state is also blocking the entrance of soil from South Carolina. All South Carolina commercial planting and harvesting equipment entering Louisiana must be accompanied by a DPI-issued certificate of inspection, while any nursery stock entering the state must have a soil sample and certificate from DPI indicating the sample is free of the nematode.
While South Carolina has native root-knot nematode species, the Guava is a tropical species which first appeared in Florida around 2001. Agriculture researchers were not initially concerned about the invader, but it eventually began overcoming the genetic resistance of sweet potato crops used by farms.
The US Agriculture Department has not yet studied how far the species has spread. Long admitted South Carolina researchers only stumbled across it while searching for another pest.