As temperatures rise in deep South Texas and spring rains fall across cotton and grain fields, scouting has revealed an uptick in pest pressures across the Lower Rio Grande Valley in recent days forcing many growers to advance spraying schedules in cotton and grain sorghum across the region.
In all three major Valley areas, Cameron, Hidalgo and Starr counties, Danielle Sekula- Ortiz, Extension agent- IPM, Texas A&M AgriLife Extension for District 12 in Weslaco, is reporting most of the grain sorghum in the Valley is either at boot stage or has already headed out and is now flowering. Many fields have either been irrigated in the last week or will be irrigated this week.
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Sekula- Ortiz advises growers to make certain to scout for increases in sugarcane aphid populations before they irrigate to determine if it is practical yet to consider spraying operations. So far, thresholds have not reached sufficient numbers, but she warns that day may soon be coming.
Since last week she reports growers have been seeing small sugarcane aphid colonies on sorghum leaves (5 to 15aphids per leaf) in the commercial sorghum fields they have been monitoring—but nothing that warrants spray treatment yet. Many adult, winged aphids (alates) have been flying into the fields and have started to reproduce. “However, along the river and near the coastal regions we are starting to see honeydew secretions on some leaves already.
"We have seen slightly higher colonies of 50 to 150 aphids per leaf on scattered plants in some fields," she warned. "It is critical during the next three weeks to monitor sorghum closely—every 3 to 4 days. We have received reports of some producers spraying for sugarcane aphids in recent days."
Sekula-Ortiz reports Sivanto and Transform insecticides are available for use in sorghum to treat the sugarcane aphid. Both products offer good control of the sugarcane aphid. Transform received a Section 18 for use on sorghum—effective April 8, 2016, and expiring April 8, 2017.
“Note that when making a Transform application you have to have a copy of the label in hand. Also note that the Section 18 label for Transform this year stipulates that the product Transform cannot be applied more than three days pre-bloom until after seed set.”
Sivanto also received a 24c label reducing its pre-harvest interval (PHI) from 21 days to 14 days (same as Transform).
For those who were not able to attend the RGV SCA meeting last week or for those who want to take a second look at the presentations you can find them available at: http://southtexas.tamu.edu/programs-and-services/ipm/
VALLEY COTTON UPDATE
Most of the Valley’s cotton crop has just started squaring with the exception of some older cotton farther along.
"In cotton we have been finding thrips, cotton aphids, whiteflies, flea hoppers, spider mites and beneficials," Sekula- Ortiz reported this week. "We are also seeing high numbers of cotton aphids in the Mid-Valley area and down by the Rio Grande River. If the aphids continue to increase in numbers and we do not receive a hard rain, spray might be warranted especially on the younger 5 to 7 true leaf cotton."
She says several cotton fields this week and last week were being sprayed for cotton aphids and thrips. These pests are prevalent in the seedling cotton where larger numbers of thrips in the Mid Valley area are being reported where onion fields are present. Producers are also reporting a few whiteflies in Weslaco, the Mercedes area and south along the river.
Red spider mites were also present in cotton in the Harlingen area this past week.
"If we continue to have dry weather it will be critical to scout younger cotton for red spider mites to avoid stunted growth from excessive feeding," Sekula- Ortiz warns.
All three counties are also starting to pick up on fleahoppers "but very few at this time." She says the next four to five weeks will be critical to monitor for fleahoppers as research shows that as many as 85 percent of total bolls harvested come from squares set during this time period. “Again, when scouting for fleahoppers, each time you sample (once or twice weekly is good) you will want to check about 25 terminals in at least four locations of a field starting when the first squares are appearing.
“If you notice anywhere from 15 to 25 fleahoppers per 100 terminals with squares being lost—rule of thumb: 10 percent the first week of squaring, 15 percent the second week of squaring, and 25 percent the third week of squaring, with treatment rarely needed after first bloom—treatment is justified.”
Insecticides available to treat fleahoppers include Assail, Centric, Intruder, Carbine and several others.