Estimating the critical level of kernel damage to impact field corn yield
Estimating the critical level of kernel damage to impact field corn yield
Monday, November 17, 2014: 9:12 AM
E146 (Oregon Convention Center)
The first generation Bacillus thuringiensis (Bt) traits in field corn, YieldGard® and Herculex®, demonstrated minimal activity against corn earworm feeding on grain in ears. However, the newer transgenic Bt corn hybrids express Genuity® and VT Triple Pro®, Genuity® and SmartStax®, and Agrisure Viptera® traits with significant efficacy against corn earworm infesting corn ears. Preliminary evaluations have demonstrated that these traits are effective at reducing ear damage from corn earworm, however yield responses have been variable. Studies were initiated during 2013 using simulated damage methods to determine the critical level of kernel damage required to impact corn yield. Individual ears were assigned randomly to the simulated damaged treatments which included 0, 10, 20, 40, 60, or 100 kernels. A minimum of 20 ears were used for each treatment. Damage treatments were imposed at milk stage to avoid interference with pollination. The first kernels from the tip that would mature were estimated on each ear. The number of kernels to be damaged began at that point and proceeded toward the base of the ear. Kernels were damaged manually with a sharp object or finger nail. After damage was imposed, each ear was surface sterilized with 95% ethanol and covered with a corn ear pollination bag to minimize fungal growth. Each ear was hand harvested and shelled individually into 4 sections based upon length, with section 1 representing the ear tip. The mean grain weight, number of kernels, and weight of individual kernels was determined for each ear section. Preliminary data for the 2013 trials were subjected to linear regression using (SAS Institute 2010). During 2013, a significant relationship between kernel damage and yield was observed. Preliminary analysis of the 2013 data indicated a significant relationship between kernel damage and yield. Based on the regression equation, for every kernel damaged (ca. 0.22g) of grain yield was lost. Additional studies are planned for 2014.
