The Georgia Agricultural Experiment Stations
College of Agricultural and Environmental Sciences
The University of Georgia

1999 Corn Performance Tests
Research Report #661
November, 1999

Insect Screening Results

Evaluation of Corn Hybrids for Resistance to Insects

N. W. Widstrom

Environmental conditions in Georgia during the 1999 growing season were unfavorable for buildup of insect populations large enough to cause serious damage to corn. Generally, this damage is greatest in late-planted corn left in the field for an extended period past maturity.

Hybrids resistant to insects are recommended for planting and are presently the only economical means, in late plantings, for the reduction of damage by corn earworm, fall armyworm, maize weevil, and pink scavenger caterpillar. Consult your local county agent and/or extension entomologist for additional control recommendations for other insects.

Percent yield losses attributable to all insects for individual hybrids varied from 0.4% to 3.9% and are reflected by VG, G, F, P, and VP ratings in the tables. Hybrids in the tests sustained average yield losses of 1.2%, and 1.9% in the full and mid-season, and short-season hybrid tests, respectively. The mean level of overall yield loss for all tests was 1.6%. Of the total loss, about 34% was attributable to ear injury by the corn earworm, 58% to the pink scavenger caterpillar, and 8% to the maize weevil. Losses to the pink scavenger caterpillar and maize weevil are based on damage by multiple generations of these insects as the corn dries in the field. Timely harvest will substantially reduce losses to these two insects.

Evaluations for resistance to corn earworm and fall armyworm, maize weevil, and pink scavenger caterpillar are given for hybrids in the tables following. Lettered ratings refer only to relative resistance to insects and are not indicative of yield. Thus, a hybrid rated poor for resistance to insects might possibly be among the highest yielders and vice versa. See the yield data in other tables for this information.

Husk tightness ratings were assigned using a scale of 1 to 5, in which 1 = very loose and 5 = very tight. No average rating was less than 2.0 or greater than 4.0; therefore, only loose, medium, and tight ratings are given in the tables.

Both the hybrid tests (mid and full-season, and short-season) were planted April 2, 1999. Plots were thinned to 20,000 plants per acre. Ratings for overall insect damage were completed during September.

Data for this section were compiled by J. M. Cook and J. C. Mullis of the United States Department of Agriculture, Agricultural Research Service, Insect Biology and Population Management Research Laboratory, and Georgia Coastal Plain Experiment Station, Tifton, Georgia.

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