Larval behavior, survivorship, and injury potential of Helicoverpa zea (Boddie), and tobacco budworm, Heliothis virescens (F.), was evaluated on cotton plants genetically engineered to express Bacillus thuringiensis (Bt) insecticidal proteins, Vip3A and Vip3A +Cry 1Ab (VipCot). Larvae (2-d-old) of both species were infested on plant terminals of vegetative or flowering stage cotton plants. Regardless of species, more larvae migrated from the plant terminals of Vip3A and VipCot plants compared to larvae infested on a conventional non-Bt cotton line (Coker 312). Larval (2-d-old) survivorship on VipCot plant structures was generally lower than that on similar structures of the Vip3A cotton line. However, H. virescens survivorship was higher than that for H. zea on similar structures of Vip3A plant. Age-specific (2 d, 4 d, 6 d, and 8 d-old larvae) survivorship was further evaluated on flower buds (cotton squares) of Vip3A and VipCot plants. Cumulative survivorship levels for both species and all larval ages were significantly lower on Vip3A and VipCot squares compared to that for Coker 312. No larvae of either species successfully pupated on VipCot squares. A limited number of H. virescens larvae completed larval development on Vip3A cotton squares.
Field trials quantified cotton fruiting form injury on these Bt lines from artificial and native infestations of H. zea or H. virescens. Larvae (L2 stage) of H. zea infested in white flowers injured an average of 8.6, 4.6, and 1.0 fruiting forms per larva on Coker 312, Vip3A, and VipCot plants, respectively. Similarly, H. virescens injured an average of 9.2, 5.9, and 0.9 fruiting forms/larva on Coker 312, Vip3A, and VipCot plants, respectively. Native infestations of both species during 2005-2007 injured fewer fruiting forms on the Bt lines compared to that on Coker 312 plants. Seasonal efficacy patterns showed the VipCot plants to be more durable with less fruiting form injury than that recorded on Coker 312 and Vip3A, especially during periods of peak insect infestations. The combination of two proteins in the VipCot line generally improved efficacy against these pests compared to that of the single protein in the Vip3A line.
| Identifer | oai:union.ndltd.org:LSU/oai:etd.lsu.edu:etd-03272008-094704 |
| Date | 27 March 2008 |
| Creators | Bommireddy, Padma Latha |
| Contributors | Patrick K. Bollich, Richard N. Story, Michael J. Stout, Guy Boyd Padgett, Billy Rogers Leonard |
| Publisher | LSU |
| Source Sets | Louisiana State University |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.lsu.edu/docs/available/etd-03272008-094704/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached herein a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to LSU or its agents the non-exclusive license to archive and make accessible, under the conditions specified below and in appropriate University policies, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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