Adult Emergence of Suspected Wheat Stem Maggot from Infested Corn Plants June 22, 2017
On June 13 we reported on an insect suspected to be wheat stem maggot infesting corn fields following wheat and rye cover crops. (See June 13 CropWatch article.) Twenty-five corn plants were sampled from these fields for dissection to isolate larvae or were transplanted into containers with cages to capture adult emergence.
On June 20, adults began emerging from these containers. They were from across the entire geographic region that was sampled. In most cases a single fly emerged from an infested plant with a few plants having two adult flies. These adult flies (Figure 1) are approximately 1/5 inch long and show all the basic characteristics of a wheat stem maggot. We are currently working with Jim Kalisch, entomology extension associate, to confirm and ensure proper identification of this pest.
Reports of wheat stem maggot infesting corn are rare. However, in 2005 and 2015 wheat stem maggots were reported damaging corn and causing 5-10% stand loss in northeast Nebraska fields. Some university researchers indicate corn as a non-host for the wheat stem maggot. To better understand the interaction between this insect and corn we have placed a number of newly emerged adults (male and female) in cages with healthy corn plants (Figure 2) to determine if they can complete their lifecycle (egg to adult) with corn as the only available host. Such information will be critical for determining the suitability of corn as a host for this pest.
Many producers and consultants may be wondering about the adults that are currently emerging from infested corn fields. As indicated earlier, little is known about the interaction between this pest and corn, but it is our opinion that these adults will leave these corn fields in search of a more suitable host. We would also expect that healthy corn plants in these fields have reached a developmental stage where infestations are unlikely to cause significant damage.