A five-year field study was conducted in Arizona to assess the long term impact of transgenic cotton expressing the Cry1Ac dð-endotoxin of Bacillus thuringiensis (Bt) on population densities of 22 taxa of foliar-dwelling arthropod natural enemies and on the effect of the natural enemy community on key pests in the system. Multi-year analyses of arthropod abundance revealed small, but statistica...

Despite the widespread adoption of Bt cotton, farmers still spray excessive pesticides in their cotton fields. In contrast to scientists who always use high quality seeds in the laboratory and/or experimental fields, farmers may plant low quality seeds with a low expression of Bt toxin. How does the expression of Bt toxin influence farmers' pesticide use? On the basis of a plot-level survey and...

Transgenic cotton that produced one or more insecticidal proteins of Bacillus thuringiensis (Bt) was planted on over 15 million hectares in 11 countries in 2009 and has contributed to a reduction of over 140 million kilograms of insecticide active ingredient between 1996 and 2008. As a highly selective form of host plant resistance, Bt cotton effectively controls a number of key lepidopteran pe...

We use a regulatory model with resistance evolution in two pests to insecticidal Bt cotton and pyrethroids (a conventional insecticide) to examine non-Bt cotton (refuge) planting requirements designed to manage Bt-resistance evolution in the midsouth. Our analysis suggests that reduced refuge requirements would enhance producer profitability, sprayed refugia are more cost effective than unspray...

The overall goal of this study is to measure the effect of the impact that genetically modified cotton varieties have had on the production efficiency of small holders in farming communities in China. We also find that the adoption of Bt cotton varieties leads to a significant decrease in the use of pesticides. Hence, we demonstrate that Bt cotton appears to be an agricultural technology that i...

Transgenic crops producing Bacillus thuringiensis (Bt) toxins kill some key insect pests and thus can reduce reliance on insecticides. Widespread planting of such Bt crops increased concerns that their usefulness would be cut short by rapid evolution of resistance to Bt toxins by pests. Pink bollworm (Pectinophora gossypiella) is a major pest that has experienced intense selection for resistanc...

This study provides the first evidence of a direct link between the adoption of a genetically modified (GM) crop and improvements in human health. Estimation of the impact of Bacillus thuringiensis (Bt) cotton adoption on pesticide use from data from a survey of cotton farmers in northern China, 1999-2001, showed that Bt cotton adoption reduced pesticide use. Assessment of a health-production f...

Cotton produces insecticidal terpenoids that are induced by tissue-feeding herbivores. Damage by Heliothis virescens caterpillars increases the terpenoid content, which reduces the abundance of aphids. This effect is not evident in Bt-transgenic cotton, which is resistant to H. virescens. We determined whether induction of terpenoids by caterpillars influences the host quality of Aphis gossypii...

Widely grown transgenic crops producing insecticidal proteins from Bacillus thuringiensis (Bt) can benefit agriculture, but adaptation by pests threatens their continued success. Refuges of host plants that do not make Bt toxins can promote survival of susceptible insects and delay evolution of resistance, particularly if resistance is inherited as a recessive trait. However, data have been lac...

Transgenic insect-resistant cotton (Bt cotton) has been extensively planted in China, but its effects on non-targeted insect species such as the economically important honey bee (Apis mellifera) and silkworm (Bombyx mori) currently are unknown. In this study, pollen from two Bt cotton cultivars, one expressing Cry1Ac/EPSPS and the other expressing Cry1Ac/Cry2Ab, were used to evaluate the effect...