Semi field trials to evaluate undersowings in maize for management of western corn rootworm larvae

Authors: SCHUMANN, MARIO - Georg August University; TAPPE, BIANCA - Georg August University; French, Bryan; VIDAL, STEFAN - Georg August University

Submitted to: Bulletin of Insectology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/30/2016
Publication Date: 6/1/2017
Citation: Schumann, M., Tappe, B., French, B.W., Vidal, S. 2017. Semi field trials to evaluate undersowings in maize for management of western corn rootworm larvae. Bulletin of Insectology. 70:63-68.

Interpretive Summary: In North America and Europe, the western corn rootworm (WCR) larvae eat the roots of corn and in high numbers can cause severe damage to corn and reduce yield. Roots from plants mixed or undersown with maize roots may interfere with the ability of WCR larvae to find the corn roots thereby lowering their survival and reducing larval numbers. Undersowing corn with perennial rye grass, Italian ryegrass, a mixture of Italian ryegrass and white clover, white clover, yellow mustard and sunflowers we found that only sunflower caused a significant reduction in larval densities, whereas the remaining five tested undersowings did not reduce larval density. Historically, undersowings have not been considered as a control measure against WCR larvae, but our study shows that sunflowers mixed with corn plants indicate a promising option as an additional control measure for WCR management.

Technical Abstract: Western corn rootworm larvae (Diabrotica virgifera virgifera) need to feed on maize roots after hatching from overwintering eggs. It was hypothesized that the roots of undersown plants mixed with maize roots disrupt the host finding of the larvae, lowering their survival and subsequently reducing larval densities. Six undersowings (Perennial rye grass, Italian ryegrass, a mixture of Italian ryegrass and white clover, white clover, yellow mustard and sunflowers) were tested with a standard maize cultivar. Semi field plots with a silt loam and peat soil mixture were set up to simulate field conditions. The larval density per plant was determined by extracting the larvae from the root core of the maize plants with a Kempson extraction system 14 – 21 days after the first larval hatch. Contrary to the hypothesis only sunflower caused a significant reduction in larval densities, whereas the remaining five tested undersowings did not result in a significantly lower larval density. White clover as an undersowing resulted in a significantly higher larval density than in the control. In conclusion, undersowings generally do not provide an alternative control measure against western corn rootworm larvae. Sunflowers mixed with maize plants indicate a promising option as an additional control measure, but would have to be tested under field conditions to confirm its potential for Western corn rootworm management.