This is the first year South Carolina grain sorghum farmers have had to deal with sugarcane aphids on a large scale. Clemson University Entomologist Francis Reay-Jones calls the sugarcane aphid one of the most devastating pests he’s seen, and it presents a great challenge because it is so difficult to control.
“The populations can expand extremely quickly and we’ve had problems in every county that we’ve had sorghum in,” Reay-Jones said at the Pee Dee Farm Field Day at the Pee Dee Research & Education Center Sept. 10 in Florence, S.C.
“One of the reasons it is such an issue is that the older chemistries registered for sorghum, dimethoate and Lorsban, only provide moderate control of sugarcane aphids."
The good news is that South Carolina was given a Section 18 Emergency Exemption Label from the Environmental Protection Agency for Transform, a new insecticide marketed by Dow, Reay-Jones said. “This is a good product and we are fortunate to have it,” he added.
In addition, another new insecticide, Sivanto, is now labeled for sorghum in South Carolina. “Both Transform and Sivanto have been highly effective in trials in other states for control of sugarcane aphid. Preliminary data from a trial in South Carolina in 2015 confirmed that these products are effective,” Reay-Jones said.
Sugarcane aphids were first detected in South Carolina in October 2014. Reay-Jones said the pest has to potential to cause significant economic damage to grain sorghum. “The insect feeds on plant sap and can seriously injure or kill plants,” he said.
“There’s a lot we don’t know about this insect,” he added. “We don’t think it over winters in South Carolina. We think it needs a live host for survival and the main weed species it develops on is Johnson Grass. Johnson Grass is everywhere but typically in a freeze it will die. We think it’s going to have to move north from Florida or South Georgia every year. But we don’t know that.”
Clemson is conducting research at both the Pee Dee Center and the Edisto Research and Education Center in Blackville on sugar cane aphids to determine their impact on sorghum in the state and to provide management recommendations.
“In addition to determining the pest status of the sugarcane aphid and exploring insecticide efficacy, research will also focus on developing sampling procedures and economic thresholds as well as identifying practices that could minimize the need to use insecticides,” Reay-Jones said.
In the meantime, Clemson Geneticist Steve Kresovich said the university is focusing on yield, stability, disease resistance, insect resistance and grain quality in its grain sorghum breeding work. “We’re looking for better varieties and better hybrids for the production system in our area that fit the system we have,” he pointed out.
Kresovich said grain sorghum has great potential in South Carolina with groups like Murphy Brown and the poultry industry needing sorghum for feed. In addition, grain sorghum is used for both syrup production and whiskey production in the Palmetto State, he said. Down the road, grain sorghum can be used for ethanol production, he added.
Clemson is working on understanding the genetics of grain sorghum. A challenge, Kresovich said, is that grain sorghum is closely related to Johnson Grass. “Johnson Grass is a really bad weed, so if we make a transgenic in sorghum, like they have in corn and sorghum, that gene would get transferred to the Johnson Grass and you would have Roundup-resistant Johnson Grass so we don’t want to use transgenics in sorghum.”