–by Anthony Zukoff — Southwest Research and Extension Center

The recent freeze and a lack of flowering sorghum has ended adult sorghum midge activity in the area. Adult midges were observed on station grounds in Garden City starting the first week of July and were still present on late flowering panicles into the first week of September.   As sorghum reaches maturity, it is easy to find evidence of midge activity even if you did not see adults when the fields were blooming.  Simply look for flattened, blank zones on the heads.  These seeds never developed because the maggots consumed them from the inside.  A general recommendation for avoiding losses due to midge is to make sure the field blooms uniformly and before mid to late August.  For comparison, in the Texas panhandle, growers are encouraged to have fields blooming no later than the first of August to avoid issues with sorghum midge.  Beginning the last week of July, sorghum on the station this year bloomed over a long period of time, which allowed some general observations to be made regarding blooming time and midge damage once heads reached maturity.  Plants that began blooming on July 25 were free of noticeable midge damage.  Those that began blooming around August 5 experienced damage to the upper 1/5^th of the panicles.  A final location that bloomed very unevenly starting August 11 experienced significant losses with most panicles being almost completely blank (Figure 1).  While midge damage is very easy to spot on varieties with red panicles, it might be more challenging to see on varieties with white panicles; however, damage will show up the same regardless of color (Figure 2).  In addition to midge damage, headworm and bird damage were prevalent in the later blooming field but are easy to differentiate (Figure 3).  If you have observed midge damage this season anywhere in the state, consider sending me a report including an estimate of acreage impacted and panicle damage.  For additional information and control options, please refer to the Sorghum Insect Management Guide.  https://bookstore.ksre.ksu.edu/pubs/MF742.PDF

Figure 1.  From left to right: example of undamaged panicle from plants that began blooming July 25, slightly damaged panicles from plants that began blooming August 5 and severely damaged panicle from plants that began blooming August 11.

Figure 2. White panicle variety: undamaged head on the left severely damaged head on the right from a plant blooming the first week of September.

Figure 3. Various types of damage to sorghum heads.  Left to right: undamaged head, severe sorghum midge damaged head, a head with heavy bird damage and on the right, a head exhibiting headworm damage.

–by Jeff Whitworth — Field Crops

Sugarcane aphids are still quite active throughout the eastern 2/3rd’s of Kansas in fields that still have some green leaves. These aphids are continuing to migrate in and almost as soon as they land on green leaf tissue, they start producing the tiny nymphs (see fig 1-just produced nymphs with winged female that produced them). These aphids are still infesting sorghum but, so far, have not caused any problems throughout northcentral Kansas. It is getting late enough in the growing season that they should not have enough time to increase to the point where they will be a problem.

Figure 1: SCA nymphs and mother (photo by Cody Wyckoff)

Figure 2 shows an area outlined by a marker, on the underside of a sorghum leaf that was infested by a substantial (200+) colony of sugarcane aphids in early September but was subsequently eliminated by natural causes-no insecticides. This has been typical for the last 3 years, i.e. sugarcane aphids migrate into Kansas, starting in about mid-July and continue until late October, and establish small isolated colonies but with very few areas actually developing significant populations that require treatment.

Figure 2: Underside of leaf previously infested by SCA colony (photo by Cody Wyckoff)