INSECT SCREENING RESULTS

Evaluation of Corn Hybrids for Resistance to Insects

N. W. Widstrom and B. R. Wiseman

Environmental conditions in Georgia are normally favorable for buildup of insect populations large enough to cause serious damage to corn. Generally, this damage isgreatest 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 0.5% to 7.3% and are reflected by VG, G, F, P, and VP ratings in the tables. Hybrids in the three tests sustained average yield losses of 1.4%, 2.2%, and 3.1% in the preliminary and full-season, mid-season, and short-season hybrid tests, respectively. The mean level of overall yield loss for all tests was 2.6%. Of the total loss, about 32% was attributable to ear injury by the corn earworm, 43% to the pink scavenger caterpillar, and 25% 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.

Each of the three tests of hybrids (preliminary and full-season, mid-season, and short-season) was planted April 9, 1997. Plots were thinned to 20,000 plants per acre. Ratings for overall insect damage were completed during September 16-18, 1997.

Data for this section were compiled by L. G. Adcock, J. M. Cook, J. C. Mullis, and J. L. Skinner 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.






Tifton, Georgia: Short-Season Corn Hybrids, 1997 Evaluations for Resistance to Insects and Other Traits

------------------------------------------------------------------------ Overall Resistance to Insect Injury2 ------------------ Company or Hybrid Husk Days to 2 or Brand Name Name Tightness1 Anthesis 1997 more years ------------------------------------------------------------------------ Pioneer 3245 M 72 VG G Pioneer 31b13 M 75 G - Asgrow RX770 M 70 G - UAP DG-5516 M 71 G F Southland EXP-1497111 M 70 F - Terra E1154 M 70 F - Gutwein 2810 M 72 F - Southland SS-3115 M 73 F - Pioneer 32K61 M 70 F - Southland EXP-1497007 M 71 F - Pioneer 3320 M 71 F - UAP Funk's G5581 M 70 F F Northrup King NX7305 M 71 F - HyPerformer HS9843 M 72 F G Asgrow RX897 M 70 F - Southland EXP-1497009 M 74 F - Southland EXP-1497005 M 73 F - DeKalb DK668 M 72 F G Northrup King N7931 M 70 F P Southland SS-2112 M 72 F - AgraTech EX6714 M 70 P - Cargill 7512 M 70 P - AgriPro AP9707 M 70 P - AgraTech EX6712 M 69 P - AgraTech 787 M 72 P F Southland EXP-1497003 M 72 P - AgraTech ATX770 L 71 P F Southland SS-2113 M 70 P - AgraTech ATX721 M 69 P - AgraTech ATX725 M 69 P - Pioneer 3223 M 72 P F Gutwein 2696 M 70 P - AgriPro AP9616 M 70 P - UAP Funk's DG-5510-A M 71 P F HyPerformer HY9646 L 72 P - Southland EXP-1497002 M 71 VP - Northrup King NX7906 M 68 VP - Mycogen 2725 M 70 VP - DeKalb DK618 M 69 VP - ------------------------------------------------------------------------ 1. L = loose husks, M = medium-tight husks. 2. Overall resistance to insect injury evaluations were made on the basis of total percent damage to the ear by one or more of the following insect categories: corn earworm and fall armyworm, maize weevil, and pink scavenger caterpillar. Ratings were made on a scale from very good to very poor, where VG = very good, G = good, F = fair, P = poor, and VP = very poor.





Tifton, Georgia: Mid-Season Corn Hybrids, 1997 Evaluations for Resistance to Insects and Other Traits

------------------------------------------------------------------------ Overall Resistance to Insect Injury2 ------------------ Company or Hybrid Husk Days to 2 or Brand Name Name Tightness1 Anthesis 1997 more years ------------------------------------------------------------------------ UAP Funk's G-5688 M 71 VG - Northrup King N8811 T 70 VG G DeKalb DK683 M 70 G G Northrup King 4714 T 72 G G Northrup King N 83-R7 M 69 G - DeKalb DK687 T 70 G - DeKalb DK706 T 70 G G Southland SS-5119 T 70 G - Pioneer 3146 M 71 G G Cargill X8502 T 70 G - HyPerformer HS9944 M 72 G F AgraTech ATX999 M 72 G F DeKalb DK714 M 70 G G Pioneer 3167 T 72 G G Terra TR 702E T 72 F G HyPerformer HS9977 M 71 F F AgraTech EX6890 T 70 F - Terra TR1185 L 71 F F Mycogen 2815 T 70 F - Southland SS-4116 L 69 F - Mycogen 8460 L 72 F F Terra TR1167 T 72 F F Asgrow XP9317 M 71 P - Southland SS-4120 M 69 P - Terra E1186 T 70 P - UAP DG-5670 M 73 P F Pioneer 3163 M 72 P P AgriPro AP9909 M 70 P - Mycogen X2888 M 71 P - HyPerformer HY9919V L 70 P F Cargill 8011 L 68 P - ------------------------------------------------------------------------ 1. L = loose husks, M = medium-tight husks, T = tight husks. 2. Overall resistance to insect injury evaluations were made on the basis of total percent damage to the ear by one or more of the following insect categories: corn earworm and fall armyworm, maize weevil, and pink scavenger caterpillar. Ratings were made on a scale from very good to very poor, where VG = very good, G = good, F = fair, P = poor, and VP = very poor.





Tifton, Georgia: Preliminary and Full-Season Corn Hybrids, 1997 Evaluations for Resistance to Insects and Other Traits

------------------------------------------------------------------------ Overall Resistance to Insect Injury2 ------------------ Company or Hybrid Husk Days to 2 or Brand Name Name Tightness1 Anthesis 1997 more years ------------------------------------------------------------------------ Pioneer 3085* M 72 VG G Terra TR1226* L 73 G F Greenwood 7412* M 75 G - Greenwood 6415* M 76 G - AgraTech X71629 L 74 G - AgraTech X71611 L 72 F - AgraTech X71651 M 71 F - ------------------------------------------------------------------------ 1. L = loose husks, M = medium-tight husks. 2. Overall resistance to insect injury evaluations were made on the basis of total percent damage to the ear by one or more of the following insect categories: corn earworm and fall armyworm, maize weevil, and pink scavenger caterpillar. Ratings were made on a scale from very good to very poor, where VG = very good, G = good, F = fair, P = poor, and VP = very poor. * Full-season hybrids.