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ARS Home » Southeast Area » Tifton, Georgia » Crop Genetics and Breeding Research » Research » Publications at this Location » Publication #309951

Research Project: Genetic Improvement of Maize and Sorghum for Resistance to Biotic Stress

Location: Crop Genetics and Breeding Research

Title: Multiple insect resistance in 70 commercial corn hybrids - 2013

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: 11/1/2013
Publication Date: 11/1/2013
Citation: Ni, X., Toews, M.D., Buntin, G. 2013. Multiple insect resistance in 70 commercial corn hybrids - 2013. In: A. E. Coy, J. L. Day, and J. D. Gassett (eds.). Georgia Corn Performance Tests, Georgia Agricultural Experiment Station Annual Publication. 101-4.

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. Nineteen hybrids were rated as very good (VG), the highest rating for multiple insect resistance in 2013. Five hybrids were developed utilizing YHR or BHR traits (also known as Optimum® Intrasect™), and one 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. The overall insect damage was relatively low in the 2013 trial, in comparison with the previous year; 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. Multiple species of sap beetles were recorded in 2013. Corn earworm and fall armyworm feeding penetration in corn ears was between 0 and 1.7 cm, which was less than in 2012 (0 - 2.7 cm). Corn earworm and fall armyworm damage was combined because the damage was difficult to separate. Stink bug damage in 2013 was relatively low, ranging from 0 to 1.5% 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 - 2%, which is significantly higher than 0 - 0.3% in 2012, and pink scavenger caterpillar damage was about 0 - 0.5% in 2013, which is the same as in 2012 (0 - 0.5% of the kernels). Damage and losses by the sap beetles could have been caused by possibly multiple generations of these insects as the crop matures in the field. Maize weevil infestation at harvest with 19% kernel moisture was low at 0 - 7 weevils per ear. The high level of sap beetle damage, as well as relatively low level of the stink bug damage, might be caused by the frequent rainfall after pollination in 2013. In addition, cool temperature in April and May led to late pollination in 2013 (ranging from 65-74 days), and the accumulative degree days (above 60°F in April and May) were only 69% of the previous three year average. 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 2013. Husk tightness was assigned using a scale of 1 to 5, in which 1 = very loose and 5 = very tight. Because average rating for husk tightness was between 2.6 and 4.8, only medium (M) (ratings = 2.6 - 3.9), and tight (T) (ratings > 4) are given in the table. Husk extension was between 0.3 and 7.6 cm. The ear-feeding insect damage was not correlated to either husk tightness or husk extension in the 2013 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 lowest amount of insect damage, while P represents the greatest amount of insect damage in 2013. The rankings of the 70 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 control tactic, especially in late plantings, for reducing insect related yield loss, as well as quality loss related to aflatoxin contamination. Consult with your local county agent and/or extension entomologist for ad