1. Transgenic Cotton for Insect Control
Peter C. Ellsworth, Ph.D.
IPM Specialist, University of Arizona
Maricopa Agricultural Center
Maricopa, AZ, USA

2. Disclosure
Those engaged in the dialog on biotechnology should fully disclose their relationships and opinions “up front” so that audiences can consider the context.
Partial support for my research comes from companies with interests in biotechnology.
The balance of support comes from state and federal sources of competitively available public funds.

3. Disclosure (continued)
Biotechnology and its products are neither inherently good nor bad.
The specific process and each of its products should be scientifically and independently evaluated.

4. Transgenic Cotton for Insect Control
What is available now & in the future?
Origin, identity & development
Insect target(s) in the U.S.
Efficacy & utility in the Arizona system (benefits)
Safety (risks)
Resistance
Impact of gene on plant
Biodiversity
non-target effects

5. Products Available for Cotton Insect Control
Only 1 ‘trans’-gene has been commercialized
Based on the crystalline protein produced by Bacillus thuringiensis (Bt)
Developed by Monsanto as Bollgard® and incorporated into commercial varieties by several cotton seed companies (e.g., Delta Pineland Co. & Stoneville Pedigreed Seed Co.)
Sold in the U.S., Australia, Mexico, South Africa, India, China, Argentina, Indonesia

6. Bacillus thuringiensis (Bt)
Common soil bacterium
Present in nature in a variety of forms (species & strains)
Produces proteins that are toxic to insects
Commonly used in garden sprays & for commercial agriculture, including organic farming
Extremely well-known toxin in terms of human health & environmental safety

7. Bacillus thuringiensis (Bt)
Crystalline proteins are classified according to structure & have a specific nomenclature (e.g., Cry1Ac)
Cotton has been transformed with Cry1Ac (narrow spectrum; Lepidoptera only)
Protein binds with receptors in the insect gut causing pores which perforate the midgut & lead to cell leakage & insect death

8. The Transformation Coker 312
The gene of interest is spliced out of the bacterium using a vector, like Agrobacterium tumefasciens, & transferred to cotton cells grown in tissue culture
The cells are grown into a plant & then, after testing, plants are back-crossed into commercial lines to make new varieties
Recurrent back-crossing

9. BG Cotton Efficacy Young larvae present regardless of cotton type
Little difference between Bt & non-Bt (-) varieties

10. BG Cotton Kills Small Larvae
PBW larvae must feed in order to be killed.
Large larvae survive mainly in non-Bt varieties.

11. Impact on Arizona Cotton
In 1990, > 6.8 sprays were made against PBW; still, > 5% yield loss
Since 1996 when Bt cotton was introduced, it has never required oversprays for PBW control, AND
Since 1997, only 0.5 sprays have been made against PBW over all cotton acreage (Bt and non-Bt); i.e., an areawide reduction of PBW has occurred
The net reduction in insecticide use has resulted in huge savings to farmers, and large improvements to the agroecosystem in terms of beneficial insect communities & IPM

12. Safety - Resistance
Given time & exposure, insects have the capacity to overcome most insecticides. Bt cotton may be no different, however, there are safeguards:
Refugia
High-Dose Strategy
Development of additional proteins