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United States Department of Agriculture

Agricultural Research Service

Research Project: ECOLOGICALLY-BASED PEST MANAGEMENT STRATEGIES FOR WESTERN COTTON

Location: Pest Management and Biocontrol Research

Title: Pink Bollworm and Tobacco Budworm, Cabbage Looper and Beet Armyworm Larval Mortalities Fed on Bacillus Thuringiensis Cotton Pollens and Pink Bollworm Adult Mortality Fed on Sucrose Solutions Containing Cry1ac Toxin

Authors
item Henneberry, Thomas
item Jech, Lynn
item Maurer, Jamie

Submitted to: Southwestern Entomologist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 14, 2005
Publication Date: March 1, 2006
Citation: Henneberry, T.J., Jech, L.J., Maurer, J.C. 2006. Pink bollworm and tobacco budworm, cabbage looper and beet armyworm larval mortalities fed on bacillus thuringiensis cotton pollens and pink bollworm adult mortality fed on sucrose solutions containing cry1ac toxin. Southwestern Entomologist Vol 31, No. 1: 1-12.

Interpretive Summary: Cottons containing the gene or genes that mediates the production of insect toxic crystalline proteins of Bt have had a major impact on management of lepidopteran insects worldwide. Most information to date concerns the effects on Bt toxin expression in flower buds and bolls for pest insects damaging cotton fruiting forms and toxin expressed in leaf tissue for leaf feeding pests. We fed pink bollworm (PBW), tobacco budworm (TBW), cabbage looper (CL), and beet armyworm (BAW), pollens from Bollgard or non- Bollgard cottons. Bollgard cottons express the Cry1Ac toxic protein PBW and TBW were highly susceptible to the toxin in BG pollen whereas results with BAW and CL were more variable, probably because both species are inherently less susceptible to the Bollgard toxin and because plant pollens may not be acceptable sources of food for either species. Enzyme Linked Immunosorbent Assays (ELISA) were positive for all Bollgard pollen cotton samples tested. We also collected cotton nectars from extrafloral and floral nectaries of Bollgard and non-Bollgard cottons. The occurrence of positive ELISA for nectar was variable and unexplained. We fed moths 10% sucrose solutions alone or containing varying amounts of Cry1Ac protein. Feeding on the sucrose Cry1Ac solutions had no effect on male or female longevity or egg hatch. Moths fed less on sucrose solutions containing Cry1Ac protein compared to sucrose solutions alone. ELISA positive and negative moths were found and our evidence suggests that moths at least in some cases PBW moths excrete the toxic protein after it is imbibed.

Technical Abstract: We fed pink bollworm (PBW), Pectinophora gossypiella (Saunders), tobacco budworm (TBW) Heliothis virescens (L), cabbage looper (CL), Trichoplusia ni (Hubner), and beet armyworm (BAW), Spodoptera exigua (Hubner), pollens from cottons containing the Bollgard (BG) gene from Bacillus thuringiensis Kurstaki (Berliner) that produce the CrylAc toxin. PBW and TBW larvae were highly susceptible to the toxin in BG pollen; whereas, results with BAW and CL were more variable, probably because both species are inherently less susceptible to the BG toxin and because plant pollens may not be acceptable sources of food for either species. Enzyme Linked Immunosorbent Assays (ELISA) were positive for all BG pollen cotton samples tested. We also collected cotton nectars from extrafloral and floral nectaries of BG and non-BG cottons. The occurrence of positive ELISAs for nectar was variable and unexplained. We fed moths 10% sucrose solutions alone or containing varying amounts of CrylAc formulated as MVP II bioinsecticide (Mycogen Corporation, San Diego, CA). Feeding on the sucrose CrylAc solutions had no effect on male or female mortality or percentages of egg hatch. Moths fed less on sucrose solutions containing the Cry1Ac formulation compared to sucrose solutions alone. The inert ingredients in the MVP II may be a factor influencing the results. ELISA positive and negative CrylAc moths were found, and our evidence suggests that PBW moths in some cases excrete the toxin after it is imbibed.

Last Modified: 4/19/2014
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