Insect screening results: multiple insect resistance in 64 commercial corn hybrids, 2023

Authors: Ni, Xinzhi; MAILHOT, DANIEL - University Of Georgia; TOEWS, MICHAEL - University Of Georgia; BUNTIN, G. DAVID - University Of Georgia

Submitted to: Agricultural Experiment Station Publication
Publication Type: Experiment Station
Publication Acceptance Date: 11/3/2023
Publication Date: 11/15/2023
Citation: Ni, X., Mailhot, D., Toews, M.D., Buntin, G. 2023. Insect screening results: multiple insect resistance in 64 commercial corn hybrids, 2023. In: D.J. Mailhot, D. Dunn, and G. Ware. D. Buntin, X. Ni, and M. Toews (eds). Georgia 2023 Corn, Sorghum, and Summer Annual Forages Performance Tests. Georgia Agricultural Experiment Station Annual Publication. pp. 29-32.

Interpretive Summary: not required.

Technical Abstract: Commercial corn hybrids were screened for ear- and kernel-feeding insect resistance under field conditions at Tifton, GA, and the results are summarized in the following table. A total of 64 transgenic Bt hybrids were included in this year’s trial; 14 hybrids were rated Very Good (VG), the highest rating for multiple insect resistance in 2023; 17 were Good (G); 14 were Fair (F), and 19 were Poor (P) as shown in Table 1. Eight hybrids are non-Bt, which has only herbicide-resistant roundup ready (RR) trait; one has SmartStax™ (SS); two have YHR traits (also known as Optimum® Intrasect™); 25 have VC trait, or VT2P, denoting for vector-stacked transformation (VecTran or VT), which combines two (double) Bt traits into a single DNA insertion process; 13 have TC or TRE (denotes for Trecepta Technology); and 25 contains Vip3A trait, which is shown as 3110, TC or TRE (Trecepta), VIP(or Viptera), or VYHR as shown in Table 1. SmartStax™ combined multiple transgenic technologies to control both above- and below-ground insect pests, as well as for herbicide tolerance. The Optimum® Intrasect™ insect protection traits (or YHR) include a combination of two insect protection traits – Herculex® I and YieldGard® Corn Borer, while the VC or VT2P (denoted for Genuity Double PRO®) trait contains a stack of two Bt genes (Cry1A.105 + Cry2Ab2), which target foliar- and ear-feeding lepidopteran pests. For hybrids contain Vip3A trait as shown in Table 1, 3110 in hybrid names denotes for CRY1Ab + Vip3A; TC or TRE for Cry1A.105 + Cry2Ab2 + Vip3A; VIP for Viptera (Cry1Ab + Cry1F + Vip3A); and VYHR for Intrasect + Vip3A. Please refer to column of “Bt designation” in Table 1 for Bt trait packages in each hybrid. Flowering time of all entries was between 55 and 63 days after a relatively late planting (April 20, 2023) due to precipitation in April. In comparison to 2022 (53-60 days after planting), the later flowering in 2023 reflected the relatively cooler weather conditions before pollination at the Tifton location. The data from 2021 and 2022 were used for multiple year performance assessment in Table 1. Overall insect damage on corn ears in 2023 was very high on the UGA-Gibbs Research Farm when compared to the observed damage in 2021 and 2022. The six types of ear- and/or kernel-feeding insects in order of damage severity were: corn earworm and fall armyworm, stink bugs, the pink scavenger caterpillar, maize weevil, and sap beetles. Corn earworm and fall armyworm damage was measured by the length (cm) of feeding damage penetrated from the tip of the ear toward the base. Feeding penetration by natural infestation of these lepidopteran pests (from the means of the five sampled ears per plot) was between 0.3 and 5.63 cm per ear, which was much greater than the damage observed in 2022 (0-2.03 cm). Kernel-feeding insect damage was assessed by percentage (%) of damaged kernels per ear. The number of kernels per ear were estimated by multiplying the number of kernels per row by the number of rows from a representative ear for each plot. Because of individual kernel feeding insect damage was relatively low, maize weevil, stink bug, sap beetle, and pink scavenger caterpillar damage was combined, which was ranged between 0.4-12.01% of the damaged kernels in 2023. The data related to insect damage were subjected to the principal component analysis using percentage of damaged kernels and three traits related to corn earworm and fall armyworm damage, that is, husk tightness and extension, and pest penetration on corn cobs. During the field season of 2023, corn rootworm and corn borer damage was not detected at the Tifton trial. Because corn husk tightness and extension are considered important traits for ear- and kernel-feeding insect resistance, the husk features of the sampled ears were examined. Husk tightness was assigned using a scale of 1 to 5, in which