Last year, a tiny goo-oozing aphid surprised the sorghum industry by marching across a large swath of Texas, Oklahoma and Kansas into areas it had never been seen before.

Last year, a tiny goo-oozing aphid surprised the sorghum industry by marching across a large swath of Texas, Oklahoma and Kansas into areas it had never been seen before.

Before the season was over, roughly one-third of all sorghum acreage had to be treated for the sugarcane aphid at least once.

Researchers are still learning about the patterns, preferences and behaviors of this new pest, but what they do know is it can travel widely and reproduce explosively when conditions are right.

“I know that some folks in south central Kansas and in Texas are considering growing other crops instead,” said Sarah Zukoff, who is in her third year as entomologist for K-State’s Southwest Research and Extension Center in Garden City, Kansas. “They literally lost their entire crop.”

While infestations were heavy in parts of Texas, Oklahoma and Kansas, southeast Colorado was largely spared.

“We did find it in southeast Colorado in Baca County, and that was verified by an entomologist,” Zukoff said. “It was a big year for a lot of different aphids, so we had to make sure to distinguish it from the lookalikes.” The Colorado finding came very late in the season at populations well below treatable levels. It likely migrated on the wind from neighboring Oklahoma counties where the problem was worse.

The pale yellow aphids are what Zukoff calls “passive fliers.”

“Wherever the wind is going is where they will go. They are like plankton in the ocean that just go with the current,” she said.

“It’s too early to say for sure how far they will go, but their movement north and west appears to get slower once they get past Oklahoma,” she added. “We don’t know if the humidity gradient is holding them back, or if it’s the elevation. Their most westward limit we are not sure, but we did have some areas in eastern New Mexico that were above threshold last year.”

Zukoff has been speaking on sugarcane aphid monitoring and control at area meetings this winter. She will discuss the topic again at two K-State sorghum schools in Western Kansas early next month, Feb. 2 in Scott City and Feb. 3 in Phillipsburg.

According to Brent Bean, a longtime Texas A&M agronomist who has been on staff with the United Sorghum Check-off since June, sorghum growers have two primary pesticide options for treating the aphids. Both work well without harming beneficial insects.

Bayer’s Sivanto is federally approved for use in grain sorghum; Dow’s Transform was used widely last year under an emergency use Section 18 label.

The Environmental Protection Agency pulled Transform’s federal label last fall pending further review, and it’s not clear whether that will make it harder to get section 18 approval in 2016. At least one state — Texas — has already re-applied for emergency use.

It’s important to have at least two different herbicide chemistries available to avoid the development of resistance issues, agronomists say.

Cost of application of either chemical ranges from $13 to 20 an acre, Bean estimated. Farmers can skip use of an adjuvant; sorghum check-off research has shown it doesn’t improve control rates enough to justify the added cost.

“I think most people who had the problem were able to get by with one application,” Bean added, although there were exceptions where farmers had to spray twice or more.

The aphid can reduce yields substantially by sucking sap and nutrients from plants, and the sticky secretions can lead to sooty mold and create hassles at harvest.

Zukoff fielded questions from aerial applicators about successful treatment of aphids last fall when she spoke in La Junta during the annual fly-in of the Colorado Agricultural Aviation Association.

Some agronomists now recommend using a ground application. That’s because it’s necessary to get the chemical on the underside of the leaves and on the green foliage closest to the ground.

“Our recommendation is to use a ground rig with a minimum of 10 gallons of water, but preferably 15, and use some type of nozzle where you get big drops and high pressure down into the canopy,” said long-time extension sorghum specialist Rick Kochenower, who is now the national sales agronomist for Chromatin, based at their seed headquarters north of Lubbock.

Also, avoid spraying during a cool snap. “The efficacy goes way down,” he said. “The entomologists think it’s because the insects stop feeding.”

Another key is to treat aphids early because they can multiply very quickly. In the wild, sugarcane aphids are all females that reproduce asexually making multiple clones. Or as Kochenower puts it, “they are basically born pregnant.”

“As the temperature goes up, their reproduction goes up,” he said. “They will start producing young in just four or five days.”

The treatment threshold has now been established as occurring when 20 to 30 percent of the crop shows localized infestations, depending on the plant’s growth stage.

Kochenower said it is also important to control Johnsongrass next to fields, because it will harbor the insect. Sudangrass is another potential host plant.

Varieties with moderate to high aphid tolerance are available, Kochenower said, and can give producers greater peace of mind. However, they won’t repel the pest entirely.

As farmers look ahead to next year, they can take comfort from knowing the bug doesn’t overwinter without green vegetation. “We think the furthest north it will overwinter is Abilene, Texas, but there’s still some question about that,” Bean said.

Kochenower said a freeze this winter had already killed host vegetation as far south as Beaumont, Texas, about 80 miles east of Houston.

The United Sorghum Check-off invested $350,000 in sugarcane aphid research and education last year. Sorghum leaders recently agreed to make a similar investment in 2016, Bean said. The Sorghum Check-off is now distributing a handy 3-by-5-inch, 20-page pamphlet that covers all aspects of sugarcane aphid control. Bean also convened a gathering of key entomologists and agronomists earlier this winter to discuss what they’ve learned about the aphid so far.