Masters Theses

Date of Award


Degree Type


Degree Name

Master of Science


Entomology and Plant Pathology

Major Professor

Scott D. Stewart

Committee Members

M. Angela McClure, Jerome F. Grant


Research was done in 2010 and 2011 at the West Tennessee Research and Education Center in Jackson, TN to investigate how southwestern corn borer, Diatraea grandiosella Dyar, (Lepidoptera: Crambidae), when infested at different densities and growth stages, affected the yield of infested, non-Bt corn plants and neighboring Bt plants. Infesting non-Bt corn plants with southwestern corn borer larvae caused significant injury. The number of larvae infested on plants and the timing of these infestations were factors that affected the amount of yield loss. There was little compensation by Bt plants that were adjacent to infested plants.

Other studies were done in 2010 through 2012 to evaluate how silk clipping in corn affects pollination and yield. Manually clipping silks once daily had little effect on yield. Sustained clipping by either manually clipping silks three times per day or by caging Japanese beetles, Popillia japonica Newman, (Coleoptera: Scarabaeidae) on ears affected yield if it occurred during early silking. Manually clipping silks three times per day for the first five days of silking reduced the numbers of kernels per ear and total grain weight. Caged beetles reduced the number of kernels per ear and also reduced yield one test. Some compensation for this injury was observed where other kernels within the ear grew larger where clipping reduced the total number of kernels per ear.

Following either simulated or naturally occurring corn earworm, Helicoverpa zea Boddie (Lepidoptera: Noctuidae), injury to ear tips, corn ears were evaluated to determine how yield was affected by different levels of kernel injury. In 2010 and 2011, simulated corn earworm injury reduced yield when kernels were injured at the blister and milk. In 2010, there was little or no indication that other kernels within the ear compensated for this injury by getting larger. In 2011, simulated injury inflicted at both the blister and milk stage resulted in increased kernel size within the same ear. For naturally occurring injury observed on multiple corn hybrids during 2011 and 2012, our analyses showed either no or a very weak relationship between number of kernels injured by corn earworm and yield.

Files over 3MB may be slow to open. For best results, right-click and select "save as..."

Included in

Entomology Commons