Texas Agriculture April 21, 2017 : Page 8
Texas Farmers See Early Emergence of Pests
The dry and mild winter Texas experienced this year allowed farmers in many regions to get a jump-start on their corn, grain sorghum and cotton plantings. But the warmer temperatures and favorable planting conditions have also brought with them the early appearance of unwanted pests.
“The one that is on everybody’s mind right now is the sugarcane aphid,” Dr. Robert Bowling, Texas A&M AgriLife Extension assistant professor and Integrated Pest Management Extension agent, Corpus Christi, said.
As of April 10, sugarcane aphid populations had been detected on commercial sorghum in three Rio Grande Valley counties—Willacy, Cameron and Hidalgo. Farmers in that region have already been spraying fields, according to Bowling.
“Since we started earlier this year with the favorable conditions, we are actually seeing the aphid moving into sorghum about a month earlier than what we did last year,” Bowling said. “We’ve had similar conditions in the Lower Gulf Coast area—Nueces, San Patricio and Kleberg counties.”
Sugarcane aphids are a multigenerational pest and these favorable conditions could also extend their reproduction window and increase numbers, according to Bowling.
“When conditions are favorable either up front or in the tail end of the season, that just adds to the generations that could possibly occur,” Bowling said.
To reduce yield losses, farmers should be vigilant and pay close attention to field borders.
Many of the early-seeded crops are no longer protected by an insecticide treatment because residual activity is only effective 30-50 days after planting, Bowling said.
And the canopy stage of development in sorghum is very conducive to the aphid.
“We really don’t see these very rapid explosions of the aphid until the plant starts to get closer to reproductive development,” Bowling said. “That’s really when the aphid can start to increase its population very rapidly, certainly as the head pushes out and starts flowering in the grain field.”
Bowling said rain events caused a gap in the planting season, which is making aphid detection and treatment more of a challenge for some farmers.
“It’s almost like you’ve got two separate crops—early-planted sorghum, you’ve got the gap and you’ve got some later-planted sorghum,” Bowling said. “That later-planted sorghum could be challenged by a number of insects, but certainly the sugarcane aphids are going to be the ones we will need to watch closely.”
The sorghum crop is most at risk to lose big yields to sugarcane aphid populations during the flowering stage, Bowling said.
As farmers consider making insecticide applications, Bowling recommends they spray fields when aphid populations reach 50-125 aphids per leaf, with the exception of the Texas High Plains.
“When those populations hit that threshold, spray and make sure that the spray volume is enough to penetrate that canopy,” Bowling said. “That’s extremely important. The way these insecticides work, they really have to come in contact with all the leaves to be effective.”
Bowling stressed farmers who planted sorghum hybrids that are highly tolerant to sugarcane aphids still need to scout their fields.
“None of these sorghum hybrids are immune to the aphids,” Bowling said. “You still need to scout those fields, and if the aphid populations start building to high levels, then they do need to be treated.”
There are also environmental factors that could help suppress the aphid populations.
Bowling noted cooler conditions and rain will help slow reproduction. A fungus that will attack the aphids develops in high humidity levels combined with rain. He said very high temperatures typical in mid-June and July can also have a suppressing effect on the aphids.
Conditions are also favorable for aphid populations on cotton in the Rio Grande Valley and the Coastal Bend region.
“The cotton crops that were treated with insecticide seed treatment are providing some nice levels of protection,” Bowling said. “But those seed treatments won’t last forever as that crop advances into the six-, seven-, eight-week stage.”
He also said some farmers are spraying for thrips on cotton.
Bowling had not heard much pest activity on planted corn so far. But if the dry conditions continue, mites could be a concern.
“Mites really do like corn that’s under drought stress, especially corn going into reproductive development,” Bowling said.
He urges farmers to continue scouting their fields to help identify pests.