Location: Crop Genetics and Breeding ResearchTitle: Resistance to multiple ear-feeding insects in 56 commercial corn hybrids - 2009 Author
Submitted to: Agricultural Experiment Station Publication
Publication Type: Experiment Station
Publication Acceptance Date: 1/26/2010
Publication Date: 1/26/2010
Citation: Ni, X., Wilson, J.P., Buntin, G. 2009. Resistance to multiple ear-feeding insects in 56 commercial corn hybrids - 2009. In: Coy, A.E., Day, J.L., Gassett, J.D. (eds). Georgia 2009 Corn Performance Tests, Georgia Agricultural Experiment Stations Annual Publication 101, Athens, GA. Interpretive Summary: not required
Technical Abstract: During the 2009 growing season, 17 of the 56 hybrids were developed utilizing YieldGard VecTran Triple technology (abbreviated as VT or VT3), which stacks multiple traits for stalk protection, root protection and weed control in one transformation event. Five ear- and/or kernel-feeding insects and their damage were recorded in 2009. They are in the order of infestation severity: the corn earworm and the fall armyworm, the brown stink bug, the pink scavenger caterpillar, and the sap beetles. Although the brown stink bugs were abundant, few southern green and green stink bugs were detected throughout the season. In addition, no maize weevil infestation was detected on these entries at harvest with 18% kernel moisture in 2009. The combined insect damage rating shown in the table reflected cob damage by the corn earworm and the fall armyworm, as well as kernel damage by the stink bugs, the pink scavenger caterpillar, and the sap beetles. Multiple insect resistance was categorized in five groups according to the dendrogram generated by cluster analysis; they are very good (VG), good (G), fair (F), poor (P), and very poor (VP). VG represents the lowest amount of insect damage, and VP represents the greatest amount of insect damage. Losses to pink scavenger caterpillar and sap beetles were based on damage by multiple generations of these insects as the crop matures in the field. Corn earworm and fall armyworm damage was combined because the damage was difficult to separate, as was damage by pink scavenger and sap beetles. Corn earworm and fall armyworm feeding penetration in corn ears on the 56 hybrids was between 0.7 and 3.5 cm, which was lower than what we observed in 2008 (1.6 - 6.4 cm). Stink bug damage in 2009 (0.5-5.6% discolored kernels) was higher than that in 2008 (0.3-4.6%), 2007 (0.02-2%), and 2006 (0-1.5%). A period of drought around the flowering time in this study possibly led to lower corn earworm damage on cobs, but greater stink bug damage on kernels. Pink scavenger caterpillar and sap beetle damage was 0.2-1.7%, which is lower than in 2008 (0.4-7.6%), and similar to 2007 (0.1-2.6%), and 2006 (0.1-3.2%). No maize weevil infestation at harvest with 18% kernel moisture this year confirmed that timely harvest at maturity could be an effective management tool to reduce maize weevil infestation. The most important insects were the corn earworm and the fall armyworm, which caused the greatest kernel loss among all ear-feeding insects examined. Twelve entries were categorized as very good, while 9 entries were very poor. The rest of the 35 entries in between were ranked as follows: 13 entries were good, 13 were fair, and 9 entries were poor. Some of the transgenic Bt hybrids showed poor insect resistance ratings (with deep ear penetration), which could be caused by the fact that transgenic events in these hybrids only confer resistance to one species or the other but not to both species.