We recently heard from our Extension counterparts in Nebraska that they have been observing numerous fields that are infested with the wheat stem maggot. However, the crop in the infested fields is corn and not wheat. Prior to these 2017 reports, there have been just a few reports from Nebraska of wheat stem maggot infestations in corn that was planted following a rye cover crop. In wheat, the percentage of plants that are infested by the wheat stem maggot is usually fairly low. However, Nebraska Extension Entomologists Justin McMechan, Robert Wright, and Wayne Ohnesorg have observed corn fields with wheat stem maggot infestations that ranged from 2-30%.
Symptoms & Plant Damage
The infested corn displayed symptoms that were initially observed during the early vegetative growth stages. During the V2-V4 growth stages, the infested plants exhibited “dead heart” symptoms. This occurs when the maggots enter the stem and burrow upwards, causing the center leaves to die. Upon revisiting infested fields, plants were found to have no additional growth and excessive tillering in some cases (Figure 1).
Potential S.D. Impact
Although no cases have been reported yet in South Dakota, there is the potential for this pest to infest corn following rye cover crops. If you suspect wheat stem maggot infestations please contact us.
Figure 1. Wheat stem maggot infested corn (left) compared to uninfested corn (right). Courtesy: J. McMechan, University of Nebraska Extension