( Agency funded the research. Bt cotto...)Biotech cotton provides same yield with fewer pesticides

Bt cotton controls only one of Arizona's three major cotton pests. To control the other two pests, sweet potato whitefly (Bemisia tabaci) and the western tarnished plant bug (Lygus hesperus), growers use broad-spectrum insecticides and other types of insecticides known as insect growth regulators.

Carrière and his colleagues studied how Arizona farmers actually planted their crops and applied pesticides.

The researchers compared the yield and pesticide use for 40 fields of non-Bt cotton, 21 fields of Bt cotton and 20 fields of Bt cotton that was also herbicide-resistant.

In addition, each cotton field selected for the study was next to an uncultivated area. That allowed the researchers to compare ant and beetle biodiversity among the various cotton fields and the uncropped areas.

The team used Geographical Information Systems (GIS) and LANDSAT satellite imagery to map the fields and evaluate plant growth in the non-cultivated areas. Plant growth can affect the biodiversity of insects found in an area.

The researchers found that, per pesticide application, Bt cotton produced 9 percent more cotton/acre than non-Bt cotton. However, growers that planted Bt cotton used fewer applications of broad-spectrum insecticides. As a result, growers ended up with similar yields/acre regardless of the type of cotton grown. Carrière suggests that yields were similar across cotton types because the additional insecticide applications on the non-Bt fields cut down on the damage from whiteflies and western tarnished plant bugs.

To see what factors affected insect biodiversity in the cotton fields, the researchers used a type of statistical analysis called path analysis. Factors that affected biodiversity included the sandiness of the soil, use of broad-spectrum insecticides and insect growth regulators, number of cotton seeds planted per acre, and the amount and types of plants in the adjacent unc
'"/>

Source:University of Arizona