By Pat Melgares, K-State Research and Extension news service
Manhattan, KS- While there’s no reason for alarm, a pair of Kansas extension agents are at least urging the state’s sorghum producers to be on the lookout for a couple of pests that have recently shown up in this year’s crop.
Anthony Zukoff, the coordinator of the Insect Diagnostics Program at Kansas State University’s Southwest Research and Extension Center in Garden City, said the sorghum midge was recently found in the southwest part of the state.
If not for the destruction it causes, the midge is a remarkable insect. The adult lifespan of the fragile, reddish-orange fly is a mere 24-48 hours, but during that time females can lay 50-120 eggs – to the detriment of sorghum plants.
“Heads with severe midge damage take on an overall flattened appearance with blank areas,” Zukoff said. “These blank areas are where midge larva feed within the developing seeds and completely consume them.”
Zukoff said sorghum is only susceptible to midge damage during the bloom period when flowers are bright yellow. Female midges fly to blooming sorghum and crawl over seed heads, depositing eggs in the open flowers.
“Once the flowers take on a brownish rusty color, they are not attractive to females and are no longer able to be infested,” Zukoff said. “Adult midges do not damage sorghum; all yield loss is due to the larvae.”
Historically in Kansas, the midge has been considered a minor pest confined to the southeast part of the state, according to Zukoff. Kansas producers have never actively treated fields for the pest.
“However, between 2017 and 2021, there were reports of large infestations resulting in significant losses in southwest and southeast Kansas,” Zukoff said. “So far, there is no clear pattern to these events, and locations that experienced losses one year have not necessarily ended up with problems in the years following.”
Zukoff noted there are no treatment or threshold recommendations for sorghum midge in Kansas, though “states south of us recommend treatment at (a threshold) as little as 1 midge per sorghum head.”
“There are a variety of treatment options in those states, but cultural practices are shown to help reduce losses from this pest, including planting early in the season,” so that fields are blooming before mid-August.
Meanwhile, near Ellsworth, Kan., Midway Extension District agricultural agent Craig Dinkel reported a single case of the sorghum aphid (previously called the sugarcane aphid) in a farmer’s sorghum crop last week. Since then, some isolated cases have been found in other parts of Kansas.
Even so, Dinkel said “I am not foreseeing the sorghum aphid to be a widespread infestation this year.” He noted he has “checked multiple fields” and found just the one infestation.
“Right now, producers should just be monitoring their milo fields for the sorghum aphids knowing what varieties they have planted,” Dinkel said. “Many seed companies have bred tolerance into milo, but still some varieties – like the one I checked – are susceptible to the aphids.”
He adds: “Patience is key. If producers find sorghum aphids in a field, it doesn’t mean they will become a problem to spray for. Our beneficial insects have adapted to the sorghum aphids and have controlled them very well.”
More information on pests that affect Kansas farm crops is available at local extension offices.