Date of Award
Doctor of Philosophy
J. J. Tollefson
The response of corn to western corn rootworm (WCR) injury is complex and may be influenced by agronomic and environmental variation. Studies were conducted at Iowa State University from 1984-1988 to determine the influence of water, nitrogen (N), root size and regrowth, and lodging on quantity and quality of corn infested with WCR-eggs. Optimal water and N were supplied to the plots using a trickle irrigation system and broadcast vs. split-N treatments. Although above-average rainfall occurred, there was less variation in grain yields of infested plants when supplemental water was applied to the plots. Midseason dry weights of infested plants were affected by both split-N and rate applications. Midseason aboveground dry weights increased with low to moderate WCR infestation levels which may be related to greater root weights in infested plants. Root growth was increased with irrigation and N applications. In a 1984-1985 study, grain yields were more consistently related to root size and root growth after feeding than to root damage. In an artificial lodging study (1987-1988), the influence of lodging on dry weights and grain yields was greater and more consistent than was the effect of WCR infestation. In a lodged canopy, greater amounts of leaf area occurred in the lower strata and light interception was 72% of that of an upright plant canopy. The rate of light extinction was reduced in a lodged vs. an upright plant canopy. In a two year study, crude protein (CP) content was determined to quantify the effect of WCR infestation on leaf and grain quality. WCR infestation had little effect on leaf CP, but grain protein content was significantly increased in infested plants. However, less total crop protein was produced in infested plants because of reduced yields. The effect of WCR infestation on CP content was increased, and interactions with other stress treatments were more profound during a drought-stressed year. Stepwise regression procedures determined that from 70 to 86% of the variation in leaf and grain CP content could be explained by the treatment and rootworm-related measured variables. It can be concluded from this research that the impact of WCR infestation on quantity and quality of grain is greater when other stress factors are imposed on the plant.
Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/
Barbara Porter Spike
Spike, Barbara Porter, "Growth response of corn rootworm-injured plants to environmental and agronomic variation " (1989). Retrospective Theses and Dissertations. 9085.