The survival and development of the beet armyworm, Spodoptera exigna (Hubner) (Lepidoptera : Noctuidae), on conventional Roundup Ready, Bollgard I and Bollgard II

Author

Subi Jacob

Date of Award

12-2003

Degree Type

Thesis

Degree Name

Master of Science

Major

Entomology and Plant Pathology

Major Professor

Gary L. Lentz

Committee Members

Jerome F. Grant, Reid R. Gerhardt

Abstract

The beet armyworm, Spodoptera exigua (Hubner)(Lepidoptera: Noctuidae), is a sporadic, but serious late-season pest on cotton. The cultivation of genetically modified varieties of cotton, sueb as Bollgard I and Bollgard II is being explored as a possible supplement to integrated pest management programs. This research consisted of two components: I) evaluation of the survival, developmental time, and pupal weights of beet armyworm larvae reared from the first instar until pupation on conventional Roundup Ready (SG521R), Bollgard I (SG125BR), and Bollgard II (DPLX01W970R) cotton varieties, and 2) evaluation of the survival, developmental time, and pupal weights of beet armyworm larvae reared from the third instar until pupation on conventional Roundup Ready (SG521R), Bollgard I (SG125BR), and Bollgard II (DPLX01W970R).

A survival of 24.6% was observed in feeding trials with beet armyworm larvae reared from the first instar until pupation on Bollgard II cotton. A survival of 56.2% and 66.2% was observed for experiments with beet armyworm larvae reared from the first instar until pupation on Bollgard I and conventional Roundup Ready cotton varieties, respectively. The mean developmental time of the beet armyworm from the first instar until pupation was observed to be slower for those individuals reared on Bollgard II (31.7 days) when compared to larvae reared on Bollgard I (30.3 days) or conventional Roundup Ready (27.4 days) cottons. A reduced mean pupal weight was also observed for first instar beet armyworm larvae when fed until pupation on Bollgard II (0.0426 mg) in comparison to those larvae similarly reared on Bollgard I (0.0513 mg) or conventional Roundup Ready (0.0587 mg).

A survival of 34.2% was observed in feeding trials with beet armyworm larvae reared from the third instar until pupation on Bollgard II cotton. A survival of 50% and 72.4% was observed for experiments with beet armyworm larvae reared from the third instar until pupation on Bollgard I and conventional Roundup Ready cotton varieties, respectively. The mean developmental time of the beet armyworm from the third instar until pupation was seen to be slower for those individuals reared on Bollgard II (9.8 days) when compared to larvae reared on Bollgard I (7.9 days) or conventional Roundup Ready (6.0 days) cottons. A reduction in mean pupal weight was also seen for third instar beet armyworm larvae when fed until pupation on Bollgard II (0.0445 mg) in comparison to those larvae similarly reared on Bollgard I (0.0456 mg) or conventional Roundup Ready (0.0470 mg). This research contributes to our understanding of the relative efficacy of transgenic cotton varieties such as Bollgard 1 and Bollgard II with regard to minimizing the establishment of the beet armyworm on the crop and also the economic damage caused by the pest.

Recommended Citation

Jacob, Subi, "The survival and development of the beet armyworm, Spodoptera exigna (Hubner) (Lepidoptera : Noctuidae), on conventional Roundup Ready, Bollgard I and Bollgard II. " Master's Thesis, University of Tennessee, 2003.
https://trace.tennessee.edu/utk_gradthes/6615