ARS | Publication request: Assessing beet armyworm damage on Bt and non-Bt cottons by visual observations and remote sensing

Submitted to: National Cotton Council Beltwide Cotton Conference
Publication Type: Proceedings
Publication Acceptance Date: March 7, 2008
Publication Date: July 5, 2008
Citation: Greenberg, S.M., Adamczyk Jr, J.J., Armstrong, J.S. , Yang, C. 2008. Assessing beet armyworm damage on Bt and non-Bt cottons by visual observations and remote sensing. National Cotton Council Beltwide Cotton Conference, Jan. 8-11, 2008, Nashville, TN. 2005.

Interpretive Summary: Beet armyworm, as a secondary cotton pest, may likely become a major pest because the cotton boll weevil eradication proram is currently in action, and natural enemies in cotton are under high adverse pressure from multiple applications of insecticides to control the boll weevil. We evaluated damage, survival, and yield of beet armyworm, Spodoptera exigua (Hubner), populations on Bollgard II (ST 4357 BGII/RRF and AMX 1532RGII/RR), WideStrike™ (Phy 485 WRF), Bollgard® (DPL 444 BRRR), and non-Bt cottons (AMX 262R, Phy 425 RF) in the Lower Rio Grande Valley (LRGV) of Texas. Only at the end of the season (110 d after planting), the damage of Widestrike™ cotton was 1.4-fold higher compared to Bollgard II® damage.

Technical Abstract: We evaluated damage, survival, and yield of beet armyworm, Spodoptera exigua (Hubner), populations on Bollgard II (ST 4357 BGII/RRF and AMX 1532RGII/RR), WideStrike™ (Phy 485 WRF), Bollgard® (DPL 444 BRRR), and non-Bt cottons (AMX 262R, Phy 425 RF) in the Lower Rio Grande Valley (LRGV) of Texas. Experiments were conducted under natural infestations in field plots and by artificially infesting cotton in field cages where damage assessment was evaluated by visual ratings, reflectance in field cages where damage assessment was evaluated by visual ratings, reflectance spectra, and airborne color-infrared (CIR) digital imagery. Visual observations showed that season-long beet armyworm leaf damage on non-Bt cotton was 3.6-fold higher than on genotypes containing dual Bt proteins (Bollgard II® and WideStrike) and 1.5-fold higher than on Bollgard® varieties. Only at the end of the season (110 d after planting), the damage of Widestrike™ cotton was 1.4-fold higher compared to Bollgard II® damage. Ground reflectance spectra and airborne color-infrared (CIR) digital imagery were obtained from the test plots shortly before harvest. The obtained images were able to differentiate beet armyworm damage levels between genotypes containing dual Bt proteins and non-Bt cotton group of varieties.