The Georgia Agricultural Experiment Stations
College of Agricultural and Environmental Sciences
The University of Georgia
2003 Corn Performance Tests
Research Report Number 690
October 2003
Table of Contents

Insect Screening Results

Evaluation of Corn Hybrids for Resistance to Insects

M. D. Krakowsky and N. W. Widstrom

The environmental conditions in Georgia during the 2003 growing season were not conducive to the buildup of insect populations large enough to cause extensive damage to corn. Generally, late-planted corn left in the field for an extended period after maturity is most prone to insect damage.

To reduce the potential for insect problems it is recommended that hybrids with resistance to insects be planted, as these hybrids are presently the most economical means, especially in late plantings, to reduce damage of corn by corn earworm, fall armyworm, pink scavenger caterpillar, and maize weevil. 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 0.7% to 5.9% and are reflected by VG, G, and F ratings in the table (P and VP ratings are also present for some hybrids evaluated 2 or more years). The absence of P and VP reflects the less favorable environmental conditions for insect populations, though the ratings are present for some hybrids evaluated 2 or more years. Hybrids in the tests sustained average yield losses of 2.5% and 2.1% in the short-season and mid and full-season hybrid tests, respectively. Of the total losses, about 38% was due to feeding by corn earworm, 43% to feeding by pink scavenger caterpillar, and 18% to feeding by maize weevil. Losses to the pink scavenger caterpillar and maize weevil are based on damage by multiple generations of these insects as corn dries in the field, and these losses can be reduced by timely harvest of the corn from the field.

Evaluations for resistance to corn earworm and fall armyworm, maize weevil, and pink scavenger caterpillar are given for hybrids in the following tables. Lettered ratings refer to only to relative resistance to insects and are not indicative of yield. Thus, a hybrid rated poor for resistance to insects might 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 husk and 5 = very tight husk. No average rating was less than 2 or greater than 4; therefore, only loose, medium, and tight ratings are given in the tables.

Both hybrid tests were planted April 24, 2003 and were later thinned to 20,000 plants per acre. Ratings for overall insect damage were completed in early October. Data for this section was compiled by J. M. Cook and J. C. Mullis of the United States Department of Agriculture, Crop Genetics and Breeding Research Unit, Coastal Plain Experiment Station, Tifton, Georgia.