New pest found in Concho Valley sorghum crops
No control needed yet for sugarcane aphid, but situation is being closely monitored, expert says
Writer: Steve Byrns, 325-653-4576, s-byrns@tamu.edu
Contact: Rick Minzenmayer, 325-365-5212, r-minzenmayer@tamu.edu
BALLINGER – Sugarcane aphids have jumped their primary host crop sugarcane, and have landed in the Concho Valley, a Texas A&M AgriLife Extension Service expert warns.
Rick Minzenmayer, AgriLife Extension entomologist for Runnels and Tom Green counties, said the pest is not new in the U.S., but what is new is its rapidly expanding range and newly acquired taste for grain sorghum.
“The pest left the Rio Grande Valley and moved into the blacklands and northern blacklands areas of Texas earlier this summer.They were found last week in Coleman and San Saba counties,” Minzenmayer said. “Now, they’ve moved west into Runnels, Tom Green and Concho counties.
“Currently, no Concho Valley fields have been treated, but the infestations are being monitored regularly and when the crop-damage threshold is reached, an insecticide can be applied,” he said. “The Texas Department of Agriculture has issued a Section 18 emergency use permit for Transform insecticide. It is the only insecticide currently available that will provide 90-plus percent control.”
The Section 18 emergency label granted by the U.S. Environmental Protection Agency earlier this year for Transform allows for application rates from 0.75 to 1.5 ounces per acre, Minzenmayer said.
Only two applications can be used during the growing season, so proper timing and thorough crop coverage are crucial for best results, he said. The pesticide also requires a 14-day interval between application and harvest.
The sugarcane aphid, Melanaphis saccchari, was first found in Texas late last summer but has been known in Florida since 1977 and Louisiana since 1999, Minzenmayer said. Known to feed on grain sorghum in other parts of the world, they have not been recorded on grain sorghum in the U.S. prior to last fall.
The aphid damage includes death of seedling sorghum plants, reduced seed set and at harvest their sticky prolific honeydew,or excrement, can cause harvesting machinery problems,” Minzenmayer said.
“The sugarcane aphid first became a problem in Texas in 2013, starting in the Rio Grande Valley and moving up the coast and then into Louisiana and Arkansas, where it caused significant problems,” Minzenmayer said. “Being a tropical insect it was pushed back to the Valley in the winter of 2013-14. In January of 2014, entomologists in South Texas documented sugarcane aphids reproducing on Johnson grass and volunteer sorghum plants. The rest is history.”
Minzenmayer added that growers in the Rio Grande Valley have had to deal with this pest for the second year with varying results.
AgriLife Today on July 23 reported the Coleman/San Saba finds which Dr. Charles Allen, AgriLife Extension statewide integrated pest management coordinator in San Angelo, said were the first documented instances of the insect west of Interstate-35.
“Finding sugarcane aphid further west does not necessarily mean that the aphid will move into the large grain sorghum producing areas in the Rolling Plains and High Plains, but growers need to be aware that sugarcane aphids have been found west of where they were seen last year,” Allen said. “Growers should keep a close watch on their grain sorghum fields as the plants begin to head.”
The tan to cream colored sugarcane aphids initially colonize on the undersides of leaves near the bottom of plants, then move up the plant as populations increase, Allen said.
“When about 40 percent of the plants are infested, it’s time to spray,” he said. “Plants are considered infested if they have 100 or more aphids on one of the leaves.”
The U.S. Department of Agriculture-National Agricultural Statistics Service reports 3 million acres of grain sorghum in Texas — about 1.9 million acres are west of I-35.
The West Texas crop which includes the Concho Valley, is generally harvested in late August through early October and is used primarily as livestock feed, according to Minzenmayer.
For more information, contact any AgriLife Extension office.
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