By STACY CAMPBELL
Cottonwood Extension District
I received a phone call from a local farmer in Ellis County on Wednesday, June 12th. He asked if I could come look at his and some other farmers fields. They were seeing sorghum plants with some reddish/purple leaves and some leaves having a whitish coloring or light streaks on the upper leaf surface.
Accompanied by J.P. Michaud, K-State Entomologist at the Agricultural Research Center in Hays, we went and looked at the fields. Upon close inspection we found thrips.
Our wheat hosts many different insects and once it matures and dries down, those insects start looking for another home. So, it is probably not uncommon for our grain sorghum to have some thrips each year. But this year looks to be an anomaly with more thrips feeding on the sorghum than usual.
Thrips are less than 2 millimeters long (.079”) and vary in color from yellow to brown, gray or black. The ones we observed were dark. These tiny, barely visible, splinter-like insects rasp leaf surfaces with their sharp mouthparts and then feed on the juices released.
We had to peel back the leaves on the plant to find the thrips. The good news is that they should not cause any yield loss and therefore spraying an insecticide is not recommended. As a matter of fact, if your grain sorghum had an insecticide seed treatment applied to it and most if not, all do, it should give your young plants enough protection from the thrips for at least 3 weeks after planting. Plus, the feeding they do is more cosmetic than anything, and should not lead to any yield loss.
Now for chinch bugs, I just received word today from a farmer in Barton County that an agronomist there said he has never seen chinch bug pressure that bad. Farmers will need to be scouting grain sorghum and sorghum/sudan hay fields close to harvested wheat fields for chinch bugs. They will move out of mature wheat and high numbers feeding on young sorghum plants can kill them. Damage begins along the field edge bordering the wheat, but can progress into the field as rows of plants die and the bugs move to new plants. Eventually, plants will get big enough to withstand the feeding pressure, but chinch bug migrations may last up to 2 weeks.
If you have any questions, please give me a call at the Cottonwood Extension Office in Hays at 785-628-9430 or email me at [email protected] J.P. Michaud, Entomologist at the Agricultural Research Center - Hays can be reached at 785-625-3425 or email [email protected]
Stacy Campbell is a Crop Production Extension agent in the Cottonwood District (which includes Barton and Ellis counties) for K-State Research and Extension. You can contact him by e-mail at [email protected] or by calling 785-628-9430.