Submitted to: Corn Performance Tests
Publication Type: Experiment Station
Publication Acceptance Date: October 25, 2005
Publication Date: October 31, 2005
Citation: Ni, X., Krakowsky, M.D., Da, K. 2005. Evaluation of corn hybrids for insect resistance. In: A. E. Coy, J. L. Day, and P. A. Rose (eds.), Georgia 2005 Corn Performance Tests, Research Report 701, pp. 35-37. Interpretive Summary: not required
Technical Abstract: During the growing season of 2005, the environmental conditions in southern Georgia were favorable for the rapid buildup of insect populations, providing the potential for considerable damage to the corn crop. Six ear-feeding insects recorded in our trials were the southern green and brown stink bugs, the pink scavenger caterpillar, the corn earworm, the fall armyworm, and the maize weevil. While stink bug feeding before anthesis may kill developing silks and terminate kernel development by preventing pollination, stink bug feeding post-anthesis can prevent normal kernel development. Although the ear-feeding insects usually cause the greatest amount of damage in the late-planted corn, corn left in the field for an extended period past maturity could also be severely damaged by the pink scavenger caterpillar and maize weevil. In 2005 stink bugs caused the greatest percentage of injured kernels, while maize weevil damage was least observed. Percentage of all insect-damaged kernels for these hybrids varies from 1% to 11% and is reflected by a rating of very good (VG), good (G), fair (F), poor (P), and very poor (VP) shown in the table. Hybrids in the test sustained average of 5.2% of the kernel damage. Of the total damage, 65% was caused by stink bugs, 27% by the pink scavenger caterpillar, 8% by the corn earworm and the fall armyworm, and only less than 0.1% was by the maize weevil. Although the stink bug-damaged kernels might not result in a complete yield loss, the high percentage of shriveled and discolored kernels can reduce quality and increase the opportunity for infection by molds. Losses to the pink scavenger caterpillar and the maize weevil were based on damage by multiple generations of these insects as the crop dries in the field. Timely harvest can substantially reduce losses caused by these two insects. Hybrids resistant to insects are highly recommended for planting and are presently the most economical means, especially in late plantings, for the reduction of ear-feeding insect damage. Consult your local county agent and/or extension entomologists for additional control recommendations for a specific insect pest in your region. Rankings of the 67 hybrids for their resistance to the six ear-feeding insects are given in the following table. During the damage evaluation process, husk tightness ratings were assigned using a scale of 1 to 5, in which 1 = very loose and 5 = very tight. Because average rating for husk tightness is between 3.5 and 4.7, only loose (L), medium (M), and tight (T) ratings are given in the tables. The insect resistance ratings were VG=0-2%, G=2-3%, F=3-7%, P=7-10%, and VP>10%. The lettered ratings in the tables refer only to relative resistance to insects and are not indicative of yield. Please refer to the yield data in other tests for specific information. All entries were planted on April 5, 2005 and harvested on October 11, 2005. Plots were thinned to 20,000 plants per acre. Data for this section were compiled by J. C. Mullis, P. Tapp, and G. Gunawan at the Coastal Plain Experiment Station in Tifton, Georgia.