Clemson University researchers have detected the damaging sweet potato weevil in three more South Carolina counties, increasing the likelihood they could be added to a quarantine which already covers Charleston and Beaufort counties.
The insect has now been detected in Jasper, Colleton and Berkeley counties, he said. The quarantine could be extended later this year to include the new areas.
Clemson Department of Plant Industry Assistant Director Steven Long said the problem is that when the weevil does not have sweet potatoes to feed on, it can consume native Morning Glory plants and survive the winter.
“Because of the temperature variance in those coastal areas compared to farther inland, it just doesn’t get cold enough to kill those Morning Glories or those weevils,” Long said. “If the Morning Glories were to be killed out if you had a harsh enough winter, the weevils would not survive, either… Because those coastal areas don’t typically get as cold as other parts of South Carolina, that’s typically where you would see the increased risk of the sweet potato weevil overwintering and surviving.”
Long said the weevil has not been detected in any of the state’s sweet potato farms for years.
“We don’t want it to become established in sweet potato farms,” he said. “We actually did have a pretty severe winter, so that’s really unfortunate for what we found. We would have liked to have seen a lot of negative trap findings this year and be able to associate an uncommon cold winter with being able to kill out those weevils but we didn’t see that.”
The sweet potato weevil is one of the most destructive sweet potato pests in the world, capable of causing losses of up to 97 percent in a single crop. It is widespread on every continent but Antarctica — almost anywhere sweet potatoes can be grown.
“We’re going to continue to trap,” Long said. “We’re going to continue doing surveys down there to try to figure out exactly where it is. We weren’t completely surprised to find it in the counties that we found it in. But we’ve got a lot more work to do now to figure out exactly where it is in those counties.”
Long warns would-be farmers to buy sweet potato plants locally and to not move even ornamental plants from one county to another.
“That is a major threat for moving around sweet potato weevil in South Carolina and throughout the Southeast, quite frankly,” he said. “Just be aware that those plants like Morning Glory are in the same genus of plants as the sweet potato and can move the sweet potato weevil around. . . they depend on that human movement.”
Researchers are trying to determine exactly where the sweet potato weevil is before establishing quarantine in the three counties.