Calling the current “white” sugarcane aphid outbreak in Deep South Texas a crisis, Texas AgriLife Extension Integrated Pest Management specialist Danielle Sekula-Ortiz is warning Lower Rio Grande Valley sorghum growers to "brace yourself" after scouting sorghum fields this week and warns about the proliferation of the pest in other types of crops.
Sekula-Ortiz says 172 growers and guests crowded into a special meeting this week at the Texas AgriLife Research & Extension Center in Weslaco to listen to entomologist Dr. Raul Villanueva and other pest specialists provide an update on the outbreak after scouting sorghum fields in recent days revealed an explosion of aphid populations.
"Practically overnight we saw a huge jump in aphid population numbers in sorghum fields across parts of the Valley and we are beginning to see movement between sorghum fields and corn and even sugarcane. I have never seen anything blossom this fast," Sekula-Ortiz said.
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Also present at the meeting were a number of entomologists and pest management specialists from across the border in Mexico where farmers are also engaged in the same kind of battle with this new pest.
"One researcher from Mexico took the floor and told growers that farmers and officials on both sides of the border need to view this outbreak as a regional problem and not as two isolated incidents," she said.
Sekula-Ortiz has been warning sorghum growers to scout fields for the new sugarcane aphids, but she says many are still confused over the more traditional yellow sugarcane aphid and this new aphid species.
"Several growers have dealt with the larger yellow sugarcane aphid in the past and have not fully understood this new aphid represents a greater risk. We have been talking about calling this new aphid a white sugarcane aphid in order to delineate between the two kinds of similar pests," she added.
The “white” sugarcane aphid is translucent at early stages with a pale yellow tint and becomes a little darker yellow as they mature. But Sekula-Ortiz says a distinct difference is obvious once you see the two aphid varieties side-by-side. The yellow sugarcane aphid is “neon” yellow and generally larger and when scouting fields growers may find a few of the yellow aphids and hundreds of the new white aphid variety.
"These are the ones we are concerned about," she said.
Over a two week period of scouting for the new aphids and committing those results on a graph, AgriLife officials were astounded at the rapid jump in aphid numbers. Eleven large commercial sorghum fields were used to chart the outbreak and Sekula-Ortiz said in spite of scouting the test fields regularly, they felt like they were caught by surprise when population numbers suddenly skyrocketed.
"I think it was a number of factors that contributed to this population explosion—warmer weather, maturing plant stages, the initial heading of the plants and other factors. We just didn't expect it to happen this soon, though we knew we had a potentially risky outbreak."
The good news, if there is any, is that early applications of Dow AgroSciences' Transform WG are proving to be effective if applied correctly. The downside is an application increases input costs by about $6 an acre. EPA authorized a Section 18 to Texas Department of Agriculture for the use of Transform WG (sulfoxaflor) on sorghum to control the sugarcane aphid.
Sekula-Ortiz says using drops on spray booms and hollow cone nozzles to apply the chemical under the bottom leaves where aphids feed is the most effective treatment method. She also recommends using a surfactant to help ensure better coverage. A high rate of water, 10 to 20 gallons per acre for irrigated fields, is best.
"We are looking at the need for two applications for adequate control, and maybe a third application depending on the intensity of the problem in individual fields."
And that, she says, is the downside.
"Some of our larger producers in the Valley decided early on they wouldn't treat their fields because of the added costs. Some felt like they had weathered past aphid outbreaks, but over the last week or so they are beginning to understand this is not just an average outbreak of the yellow sugarcane aphid but an entirely new threat."
She advises that if scouting determines 40 out of 100 sorghum plants are infested by the new aphid, consider treating with Transform WG.
To add to concerns over the outbreak of the new white sugarcane aphid in sorghum fields across the Valley, Sekula-Ortiz says last week they began noticing winged varieties of the new aphid had migrated to corn and sugarcane test plots at the Weslaco research center.
After scouting commercial corn and sugarcane they began to spot aphids that had moved to these crops.
"At first we were just seeing a few aphids in corn and sugarcane, but over the course of a week these numbers increased rather rapidly and we are continuing to monitor the spread of the aphid to other crops beyond sorghum," she added.
Sugarcane is a year-round crop and that adds to concern over the proliferation of the new aphid variety. While population densities in corn are not alarming at this point, a greater number of the aphids are being found in sugarcane.
"One reason we are so concerned about the rapid movement of this pest is that we are getting reports of the new aphid from places like Louisiana and have heard they were found in Oklahoma late last year. At this point some are suggesting that by the end of the growing season we may see the new aphid showing up as far north as Kansas, so this is a concern that goes far beyond the Rio Grande Valley."
Sekula-Ortiz says one of the reasons for concern is that the white sugarcane aphid is a more serious threat because it can more readily spread plant viruses.
"It's a much better vector of viruses like yellow leaf virus, and that's a real concern. You know, we thought about advising growers to skip a fall planting of sorghum as a defensive strategy to help control this aphid, but now that we are beginning to realize the outbreak may include other crops like sugarcane that strategy would be ineffective. We still have a lot to learn about this pest, so our research will continue."