When farmers in the Lower Rio Grande Valley first began noticing white aphids in their grain sorghum in 2013, it wasn’t that high numbers of what were later identified as sugarcane aphids were impacting yield so much. The problem was the honeydew secreted by the insects..
That’s been a common theme as the pest has spread from south Texas across the Gulf Coast states and up into north Texas and Oklahoma. The sugary honeydew literally “gums up the works” when farmers try to combine their crop.
“When that honeydew starts to build up you’re not going to be able to get your combine through the field,” says Sebe Brown, Extension entomologist with the LSU AgCenter’s Northeast Region. “You can be running chaff through the combine that is coated in sugar water, and when sugar water hits hot, mechanical parts it turns to gum, and it gums everything up."
Brown says farmers were burning separator belts out and other components were breaking. “Guys were driving 100 yards into the field and would be completely shut down. So it’s extremely important in late season to stop honeydew accumulation.”
Since then, researchers have found that varieties that exert their heads farther from the canopy than others can be a plus because growers don’t have to run their headers through the plants. They can just cut the heads off.
Grain sorghum has been grown for many years in the Mid-South and Southwest because it’s a grain crop that doesn’t require as much irrigation as corn. Traditionally, it has sold at a discount to corn, but that changed when China began importing significant amounts of the commodity.
With grain sorghum selling at a premium to corn and requiring lower input costs, farmers in Arkansas, Louisiana and Mississippi are believed to have increased their milo plantings significantly. (USDA’s June 30 Acreage Report will provide the first survey-based estimates of grain sorghum.)
The shift to grain sorghum means many producers have not grown the crop or grown it in a long time in 2015, a subject of increasing concern for grain and IPM specialists.
Brown and David Kerns, research entomologist at the Macon Ridge Research Station at Winnsboro, La., talked about sugarcane aphid problems in grain sorghum during a stop on the Pest Management and Crop Production Field Day at the Northeast Research Station near St. Joseph, June 17.
“Looking at desiccants, if you have honeydew-coated plants, glyphosate is not going to penetrate that honeydew,” said Brown. “We had better luck with sodium chlorate with a 1 percent crop oil concentrate. That did a better job of penetrating the crop, but the easiest way to prevent that is don’t let the honeydew get ahead of you.
“Get these aphids under control and make sure you don’t get a lot of honeydew covering your plants.”
Another consideration – movement of aphids to the grain sorghum heads. “When you desiccate a plant, and it has aphids in it, they’re going to run to the heads,” said Brown. “You haven’t contributed to honeydew, but you’re harvesting aphids with your grain.
“If you’re going to control sugarcane aphids, we’d much rather see you be early than be late,” he said. “Because if you’re late, you’ll be playing catch up the entire season, and, based on the data we’ve shown, you will be losing yield with some rather small populations infesting your fields.”
For more information on sugarcane aphids in Louisiana, visit http://www.lsuagcenter.com/NR/rdonlyres/C6BA2774-31C5-41AF-8A30-9AC50CD1135A/101354/pub3369SugarcaneAphids2NDPROOF.pdf