Degree Type


Date of Award


Degree Name

Doctor of Philosophy




The trivial movements of adult corn rootworms within 5 Iowa cornfields were examined by aerially applying Sevin('(REGTM)) 4 Oil to the perimeter of 12.6-ha areas leaving the central 6.4-ha portion untreated. The initial, emerging, and final beetles per plant were determined for successive time intervals, varying from 1-5 days. The western corn rootworm was the predominant species at all sites. The sharp decline of the beetle population in the unsprayed area was attributed to movement into the spray zone. A diffusion model was modified to express instantaneous population change due to trivial movements. The average instantaneous net displacement rate of the adult population was 17 m/day with values ranging from no movement to 64 m/day. Mean daily temperature and mean beetle density had a significant positive effect on net displacement rates observed in the field;Dispersal-selection chambers, consisting of a central 40-dram plastic container connected to 3 similar compartments with Tygon('(REGTM)) tubing, were used to evaluate the relative effects of density and temperature on western corn rootworm female activity. Laboratory densities of 10, 20, and 40 females per chamber did not have a significant effect on percent dispersal rates in 3 of 4 trials. Percent dispersal was greater at higher densities in the significant trial. Significantly more activity occurred in chambers exposed to a temperature range of 28-34(DEGREES)C than in chambers at 20-26(DEGREES)C. The density-temperature interaction was not significant;The effects of intraspecific interactions on western corn rootworm female activity were examined by placing 30 females in the center compartment of dispersal-selection chambers and observing their preferences for stimuli confined in plastic zipper cases that were located in peripheral compartments. Beetles were not significantly attracted to other females confined in zipper cases, and the addition of a food attractant did not change the results. The existence of an aggregation pheromone was not supported by this study. Beetles were significantly attracted to zipper cases with corn silks, even when the beetles could not see or physically contact the food source.



Digital Repository @ Iowa State University,

Copyright Owner

Robert George Bruss



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File Size

76 pages

Included in

Entomology Commons