Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/25/1999
Publication Date: N/A
Interpretive Summary: The western corn rootworm is one of the most economically important insect pests of corn. Many different techniques have been developed for identifying corn with resistance to western corn rootworm larvae, but little has been done to compare the reliability and repeatability of these techniques. Seventeen corn cultivars were evaluated to determine the optimal method or combination of methods to more quickly reach the goal of corn rootworm resistance in corn. Although other techniques may have applicability in determining the mechanism of resistance, a direct evaluation of corn roots for feeding damage was the most consistent technique between environments. This work will impact future studies involving corn rootworm resistance to corn by allowing them to focus on the most consistent evaluation technique, feeding damage in the field.
Technical Abstract: The western corn rootworm, Diabrotica virgifera virgifera LeConte, is one of the most economically important insect pests of corn (Zea mays L.). Many different techniques have been developed for western corn rootworm host-plant resistance screening, but little has been done to compare the reliability and repeatability of these techniques. Our objective was to evaluate seventeen maize cultivars for field adult emergence, vertical roo pulling resistance, and field/greenhouse root feeding damage to determine the optimal method or combination of methods to more quickly reach the goal of corn rootworm resistance in corn. A rootworm host-search behavior bioassay was also conducted. Rank correlation of root damage in field performance among the seventeen cultivars was found between locations in both 1996 and 1997. Greenhouse root damage experiments generally did not correlate to each other or to field locations. There was no correlation in npercent reduction of root pulling force in infested vs. non-infested rows between 1997 paired-row pulling trials. There was no correlation of field root damage performance in 1996 or 1997 to the three bioassay parameters tested: area searched, distance traveled, or number of path crossovers. It appears that the rootworm host-search behavior bioassay will not be useful in differentiating hosts within a species, and greenhouse damage ratings are questionable when comparing germplasm with limited resistance. Field damage ratings, when replicated in multiple locations, should be the final test before resistance claims are made.