Stink bugs and grasshoppers are showing up in Oklahoma cotton fields, according to Terry Pitts, Oklahoma State University Extension integrated pest management specialist.
"Stinkbugs feeding on bolls may cause boll shed and/or seed damage, lint staining and yield reductions," said Pitts, who is located at the Southwest Oklahoma Research and Extension Center south of Altus.
When making management decisions on whether to treat for stink bugs, Pitts advises examining six row-feet of cotton in several locations in each field.
An average of one or more stink bugs per six feet of row can cause excessive loss of squares and small bolls and may stain lint, he said.
"Additionally, at least 50 small bolls the diameter of a quarter and smaller should be examined. If 20 percent of the small bolls have evidence of internal feeding, such as callous growth on internal boll walls and/or stained lint, and stink bugs are present, treatment should be considered.
"Bolls larger than a quarter harden enough to prevent stink bug feeding. Focus on the squares and small bolls when considering control."
Stink bugs often clump near field margins. Spot treatment provides effective control when this situation exists, Pitts said. Second through fifth instar stink bug nymphs and adults can damage bolls. Fourth and fifth instars can cause the same level of damage as adults.
Information developed by Dr. Al Bell, USDA pathologist with Texas A&M University, shows most boll rot and seed staining and hard lock are a result of insect feeding punctures. These punctures can be made by fleahoppers s well as stink bugs. With a high incidence of boll disease, there probably has been some feeding on the bolls by one of these insects, Pitts said.
He reports seeing numerous grasshoppers in Southwest Oklahoma this season and many people have asked him about how to control grasshopper depredations.
"Jerry Stoll, a consultant in Tillman County, says he has been spraying for grasshoppers in cotton that was planted following wheat,” Pitts said. "The grasshoppers were eating small cotyledon cotton plants in no-till wheat/cotton fields."
Grasshopper population increase is favored by a fairly mild, moderately dry winter followed by early spring with cool, wet weather that prevents premature hatching. If the premature hatching does not take place, it is more likely that an adequate food supply will be available after hatching occurs, Pitts said.
"Under these conditions," he said, "we would expect to have heavy populations of grasshoppers.
"Control in small acreage is difficult due to re-infestation from surrounding areas. In cases where protection of gardens is attempted, it is best to apply a product such as carbaryl (Sevin) to labeled garden plants as well as a 20 to 30 foot strip surrounding the garden. In cropland, frequent treatment of the edge of the fields and an outside strip will provide some protection."
Directions are on some Sevin insecticide labels for making a wheat bait for distribution in a wide ban along field edges hoppers must cross to get to a crop, Pitts said.
Products approved for use in cotton are Lorsban, Baythroid and Malathion. Products labeled for grasshopper control on rangeland and pastures include Sevin, Dimilin, Malathion and methyl parathion.
To obtain more in-detail information on this subject, refer to the NTOK Cotton website www.ntokcotton.org. Pitts' can be reached at his cell phone 580-482-0208 and the Extension Center phone 580-482-8880. His email address is firstname.lastname@example.org.
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