(07/22/20) BATON ROUGE, La. — Louisiana sugarcane growers received an exemption to use an insecticide to combat severe aphid infestations.
The Louisiana Department of Agriculture and Forestry submitted the crisis exemption, and the Environmental Protection Agency approved the temporary use of Sivanto (flupyradifurone) in Louisiana sugarcane.
Sugarcane farmers can use it from July 22 to Aug. 5, 2020.
“Infestations of the sugarcane aphid and the yellow sugarcane aphid have been severe in many fields across the industry this summer,” said LSU AgCenter entomologist Blake Wilson. “These infestations have produced heavy sooty mold and leaf yellowing.”
Both species produce the honeydew that allows for sooty mold development, but it is primarily the yellow sugarcane aphid that causes leaf discoloration, he said.
The effect of aphids on sugar yields is not well understood, but reduced growth can occur in fields suffering from heavy infestations.
Observations suggest the presence of sooty mold reduces the efficiency of chemical ripeners, resulting in low sucrose recovery during milling, Wilson said. Research efforts to determine yield effects have been hindered by the lack of effective insecticides.
“Prior to the crisis exemption of Sivanto, treatment of aphid infestations was not recommended because pyrethroids registered for use in sugarcane are not effective against aphids,” he said.
Sivanto is effective against both aphid species as well as the West Indian canefly, Wilson said. No economic threshold or scouting protocol has been determined for aphids, and the insecticide should be applied only if infestations are observed to be increasing.
“Aphid infestations can decline naturally late in the summer, particularly under wet conditions, and controlling declining infestations is not likely to provide economic returns on insecticide costs,” he said.
Priority should be placed on protecting fields that will be harvested early and will require substantial ripening to obtain acceptable sugar yields. Insecticide applications can prevent further sooty mold development, but heavy rain is needed to remove sooty mold that has already formed.
The LSU AgCenter and the LSU College of Agriculture