Response of Bt and non-Bt cottons to high infestations of bollworm (Helicoverpa zea Boddie) and tobacco budworm (Heliothis virescens (F.)) under sprayed and unsprayed conditions

Authors: Allen, Clint; Luttrell, Randall; Little, Nathan; Parys, Katherine; Perera, Omaththage

Submitted to: Agronomy
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/12/2019
Publication Date: 11/15/2019
Citation: Allen, K.C., Luttrell, R.G., Little, N., Parys, K.A., Perera, O.P. 2019. Response of Bt and non-Bt cottons to high infestations of bollworm (Helicoverpa zea Boddie) and tobacco budworm (Heliothis virescens (F.)) under sprayed and unsprayed conditions. Agronomy. 9(11):759. https://doi.org/10.3390/agronomy9110759.
DOI: https://doi.org/10.3390/agronomy9110759

Interpretive Summary: Cotton varieties expressing insecticidal toxins (Bt cotton) and non-Bt cotton were infested with bollworm and tobacco budworm moths inside of large field cages (0.04 ha) during the summers of 2011 and 2012. Both early-maturing and full-season cotton lines were used to measure the possible need for supplemental use of insecticides for caterpillar. Depending on sample date, plots averaged up to 13 eggs per plant after moth release. Fruit survival within-season and at-harvest was carefully mapped on individual plants within comparative plots of all cottons untreated and sprayed with two different insecticides following insect infestations. Differences among cotton maturity groups were not consistently obvious, but early-maturing Bt cottons were among the higher yielding experimental plots both years. Average harvested fruit ranged from 0.3 to 7.5 bolls per plant for plots during 2011, while during 2012, plots ranged from 0.7 to 6.0 open bolls per plant. Bt cottons generally protected fruit from insect damage and resulted in final yields comparable to those of insecticide sprayed Bt and non-Bt cottons. Unsprayed non-Bt cottons were significantly damaged by insects in these high-infestation environments.

Technical Abstract: Early-maturing and full-season Bt and non-Bt cottons were exposed to high densities of tobacco budworm (Heliothis virescens F.) and bollworm (Helicoverpa zea Boddie) in 0.04 ha field cages during the summers of 2011 and 2012 to measure the possible need for supplemental use of insecticides on Bt cotton. Depending on sample date, plots averaged up to 13 eggs per plant after moth release. Fruit survival within-season and at-harvest was carefully mapped on individual plants within comparative plots of all cottons untreated and sprayed with lambda-cyhalothin (0.0448 kg a.i./ha) or chlorantraniliprole (0.1009 kg a.i./ha) following insect infestations. Differences among cotton maturity groups were not consistently obvious, but early-maturing Bt cottons were among the higher yielding experimental plots both years. Average harvested fruit ranged from 0.3 to 7.5 bolls per plant for plots during 2011, while during 2012, plots ranged from 0.7 to 6.0 open bolls per plant. Bt cottons generally protected fruit from insect damage and resulted in final yields comparable to those of insecticide sprayed Bt and non-Bt cottons. Unsprayed non-Bt cottons were significantly damaged by insects in these high-infestation environments.