Bugs weren’t always a concern on Spence Pennington’s 10,000 acres of sorghum in Raymondville, Texas, despite the sub-tropical climate.
“We used to consider it a relatively insect-tolerant crop, but that’s changed this year and last year,” Pennington told DTN. “In years past, cotton was our big spraying crop — now we’re spraying grain sorghum for insects multiple times and we spray cotton significantly less. The tables have turned.”
The arrival of a baffling new sorghum pest, the sugarcane aphid, and the usual mix of midge, sorghum headworm and stink bugs, are adding costs to the traditionally low-maintenance crop, farmers and experts told DTN.
Most sorghum growers like Pennington aren’t letting the bugs get them down — sorghum acreage still saw a heady jump of 24% to nearly 9 million acres in 2015. But the challenge of a new pest in sorghum could hamper the crop’s chances of competing with corn and soybeans for a larger share of acres in the affected Southern states, said Justin Weinheimer, crop improvement director for the Sorghum Checkoff.
“The growth potential going from 2014 to 2015 was hindered by fear of the sugarcane aphid,” Weinheimer said. “It certainly has to do with economics, but I think it also has a lot to do with the unknown.”
SURPRISE ARRIVAL
This species of aphid has fed solely on sugarcane fields in the U.S. for more than three decades, so no one anticipated that it would ever become a sorghum pest.
Then, in 2013, the insect abruptly gained an appetite for grain sorghum and began to feast on Texas sorghum fields.
“We still don’t know exactly what happened,” explained Texas A&M entomologist Raul Villanueva. One theory suggests that the aphid made what’s known as a host shift, which has happened with other species of the aphid. The other possibility is that a new species of sorghum-eating aphid arrived here on imported grain from South America or Africa, Villanueva said.
Regardless of its origin, the aphid has proved a daunting pest for sorghum growers. Since 2013, it has spread as far north as southern Kansas and as far east as South Carolina. Villanueva saw some untreated fields lose their entire crop in south Texas last year, and yield losses from 30% to 50% were not unusual.
However, the sugarcane aphid’s permanence as a pest in sorghum is still far from certain. Pest populations built up more slowly this summer, most likely a result of the heavy rains that have bogged down much of the pest’s Southern habitat, Villanueva said. As drier weather prevails in these regions, the aphid is rebounding and spraying costs are picking up once again.
A PRICEY NEW PEST
The sorghum industry has scrambled to cobble together treatment and management options, as scientists struggle to understand the aphid’s rapid colonization of sorghum.
Thanks to a Section 18 emergency exemption in response to the aphid, Dow AgroScience’s Transform WG insecticide has been approved for use in sorghum in multiple states since 2013. In 2015, Bayer CropScience added another insecticide, Sivanto, to sorghum growers’ chemical arsenal.
Central Texas farmer Josh Birdwell said Transform performed well last year, but many still struggled to manage the aphid. Without an established spraying threshold, panicked growers sprayed at the first sight of the tiny insects in 2014.
The aphids built up again quickly and growers like Birdwell had to spray every acre a second time. “It was a learning curve,” he said.
Jim Massey, who farms near Robstown, Texas, agreed that there was a lot of over-application last year, “but I think people learned from that and I think you could possibly get by with one spray in the future.”
Sorghum’s traditionally low input costs usually make the crop a cheaper — and thus competitive — option compared to its fellow grain crops, but the aphid changed that dynamic last year, Birdwell said.
He estimated that between multiple insecticide applications by airplane and a shot of Roundup at the end of the season to dry the sorghum down and evict the aphids, he spent an additional $60 to $70 per acre.
That cost doesn’t reflect the lost time and fuel spent at harvest, he added. Aphids leave a sticky honeydew on plants that forced Birdwell to halt work and power wash the combine twice a day during harvest. “I can tell you it cut our harvest progress down by at least 50%,” he said.
THE COST OF NON-GE: MORE MANAGEMENT
Massey is content with sorghum’s status as a non-genetically engineered (GE) grain for now. The crop’s traditional breeding has kept seed costs low and opened up important new markets, like China and the domestic gluten-free food industry. But the crop does require more management, he conceded.
“Since we’ve gotten the Bt gene, cotton tends to need a lot less spraying than it used to,” he said. In contrast, insecticide costs can pile up on his sorghum acres. “Typically when I budget, I budget one round of spraying for midge, one for headworms, one for stink bugs, and now, a new one for the aphid.”
In a year when insects are plentiful, this spraying schedule can add $25 to $35 per acre. Moreover, in a wet year like 2015, growers may have to add $6 or more per acre for every application made by airplane.
However, these sorghum input costs are more easily controlled from season to season compared to GE crops like cotton, Massey said. “In sorghum, it’s true that out-of-pocket costs can be higher, but if your crop potential is low and it’s not worth it, you don’t have to spend that money on it,” he explained. “But with cotton, all your costs are front-loaded because you pay for that technology in the seed — the Bt gene and the Roundup Ready technology — so you pay no matter what the crop looks like.”
THE APHID: A TEMPORARY SETBACK?
Despite sorghum’s overall acreage jump this year, the threat of sugarcane aphids was enough to cause some Texas farmers to walk away from the crop.
“A lot of guys in our area switched to corn this year because of the aphid and the ease of growing a herbicide-tolerant crop,” Birdwell said of growers near his Malone, Texas, operation. “I actually cut back a little bit myself because of the aphid, from 1,800 sorghum acres last year to 1,200 this year.”
Villanueva saw some farmers switch to sesame, sunflowers and corn this year, but he thinks many will return. Best management practices will be fine-tuned as research continues, he said. Company and university scientists have already identified and marketed a few aphid-tolerant varieties, and they are likely to uncover more in the coming years.
Birdwell, at least, has no plans to stray from the crop.
“I’m not going to quit growing sorghum,” he said. “I believe in staying diversified. I may be the odd man out in my area, but I think these other guys will come back around.”
