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ARS Home » Southeast Area » Tifton, Georgia » Crop Genetics and Breeding Research » Research » Publications at this Location » Publication #314207
Title: Multiple insect resistance in 77 commercial corn hybrids - 2014

Author
item Ni, Xinzhi
item TOEWS, MICHAEL - University Of Georgia
item BUNTIN, G. DAVID - University Of Georgia

Submitted to: Agricultural Experiment Station Publication
Publication Type: Experiment Station
Publication Acceptance Date: 11/15/2014
Publication Date: 11/15/2014
Citation: Ni, X., Toews, M.D., Buntin, G. 2014. Multiple insect resistance in 77 commercial corn hybrids. In: J.D. Gassett, Dunn, D., Coy, A.E., Jordan Jr., H., Day, J.L. (eds.), Georgia 2014 Corn Performance Tests, Georgia Agricultural Experiment Stations, Annual Publication 101-6.

Interpretive Summary: not required

Technical Abstract: Commercial corn hybrids were screened for ear- and kernel-feeding insect resistance under the field conditions at Tifton, GA. Twenty hybrids were rated as very good (VG), the highest rating for multiple insect resistance in 2014. Two hybrids were developed utilizing YHR traits (also known as Optimum® Intrasect™), and four hybrid was developed with Genuity VT Triple PRO (abbreviated as VT3P). The Optimum® Intrasect™ insect protection traits include a combination of two insect protection traits – Herculex® I and YieldGard® Corn Borer, while the VT3PRO traits contain a stack of three Bt genes. Two Bt genes are targeted for lepidopteran insect pests and the third gene is for the rootworms. Overall insect damage was relatively high in the 2014 trial. The six groups of ear- and/or kernel-feeding insects in the order of infestation severity were: corn earworm and fall armyworm, stink bugs, sap beetles, pink scavenger caterpillar, and maize weevil. Corn earworm and fall armyworm damage was combined because the damage was difficult to separate. Feeding penetration by these caterpillar pests in corn ears was between 0.2 and 4.3 cm, which exceeded damage observed in 2013 (1.7 cm). Multiple species of sap beetles were recorded in 2014. Stink bug damage in 2014 was relatively high, ranging from 0.2 to 4% of the kernels per ear. The highest percentage of stink bug-discolored kernels in the previous five years ranged between 0.8 and 5.6%. Sap beetle damage was 0.4 – 1.1%, which is lower than 0 - 2% in 2013, and pink scavenger caterpillar damage was about 0 - 1% in 2014, which was greater that in 2013 (0 - 0.5% of the kernels). Maize weevil infestation at harvest with 18% kernel moisture was very low at 0 - 2 weevils per ear. The low level of sap beetle damage, as well as relatively high level of the stink bug damage, might have been influenced by weather conditions in 2014. Because husk tightness and husk extension are considered important traits for ear- and kernel-feeding insect resistance, the husk features of the sampled ears were also examined in 2014. Husk tightness was assigned using a scale of 1 to 5, in which 1 = very loose and 5 = very tight. Average ratings for husk tightness were between 2.8 and 3.9, which were all considered medium for husk tightness. Husk extension was between 0.1 and 4.9 cm. The ear-feeding insect damage was correlated to husk extension, but not to husk tightness in the 2014 data. Multiple insect resistance was categorized in four groups according to the insect damage ratings on corn cobs and kernels; they are very good (VG), good (G), fair (F), and poor (P). VG represents the least amount of insect damage, while P represents the greatest amount of insect damage. The rankings of the 77 hybrids for multiple insect resistance in the table was based on the results of the principal component analysis using corn husk extension and tightness, and damage caused by corn earworm and fall armyworm, stink bugs, sap beetles, pink scavenger caterpillar, and maize weevil. The lettered ratings in the table refer only to relative resistance to insects and are not indicative of yield. Please refer to other reports for yield data. Hybrids resistant to multiple insects are highly recommended for planting and are the most economical insect control tactic, especially in late plantings. Increased insect damage can lead to yield loss, as well as quality loss related to aflatoxin contamination. Consult with your local county agent and/or extension entomologist for additional control recommendations for a specific pest in your area. The trial was planted on the University of Georgia Gibbs Research Farm near Tifton, GA on April 17, 2014, and harvested August 25-28, 2014. Kernel moisture was approximately 18% at harvest. The experimental plots were thinned to 20,000 plants per acre and maintained using local Extension recommen