(Note: The following article is taken from the Kansas Insect Newsletter of August 28, 2015, issue No. 19: http://entomology.k-state.edu/doc/Newsletters/2015/KSInsectNewsletter19.pdf)
Sorghum headworm (corn earworm, fall armyworm) populations continue to cause much concern throughout south central and north central Kansas. Sorghum is most vulnerable to headworms from flowering to soft dough. The general rule is that headworms may cause 5% loss per worm per head during the approximately 2 weeks the worms are feeding directly on the grain. Early detection, while the larvae are small, is always recommended; thus, if treatment is justified, control will be achieved before maximum damage is realized. For more information on sorghum headworm and control options, see: http://entomology.k-state.edu/extension/insect-information/crop-pests/sorghum/cornearworm.html
Figure 1. Sorghum headworms. Photos by K-State Research and Extension.
The sugarcane aphid continues to spread in Kansas sorghum and has now reached as far west as Haskell County and as far north as Dickinson County. The sugarcane aphid was discovered in Edwards County on Aug. 28. Populations are low in these counties so far, but fields in these areas should be monitored closely. Producers can contact their local Extension agent if they discover the sugarcane aphid or need help identifying aphids in sorghum.
Of these, light-colored corn leaf aphid and light-colored greenbugs tend to be the aphids that are most confused with the sugarcane aphids. The nymphs can be especially hard to differential without magnification.
Greenbugs have dark feet, dark antennae, but light-colored cornicles (tail pipes). Greenbugs will often have a green stripe down their backs, but this can be hard to see in light-colored aphids. The sugarcane aphid also has dark feet and darker antennae, however it has dark cornicles and no green stripe down its back.
Thresholds have recently changed for the sugarcane aphid. For the latest threshold and scouting information for Kansas, see: http://myfields.info/sites/default/files/page/ScoutCard%20KSU%20reduced%20v3.pdf
For information on chemical options, see Insecticide Selection for Sorghum at Risk to Sugarcane Aphids from Texas A&M University: http://myfields.info/sites/default/files/page/2_Insecticide_Selection_Sugarcane_Aphid_2015.pdf
Jeff Whitworth, Extension Entomology
Holly Schwarting, Entomology Research Associate
Sarah Zukoff, Southwest Area Extension Entomologist, Garden City