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Virginia Cooperative Extension -
 Knowledge for the CommonWealth

Bt Cotton Successful in Southeast US

Crop and Soil Environmental News, March 1998

Charles Hagedorn
Extension Specialist, Biotechnology
Virginia Tech,

During Bt cotton's first year of substantial commercial availability, Southeastern growers who planted the new varieties experienced significant net benefits from their Bt cotton compared to their conventional plantings, according to a survey that was recently completed. Both yield increases and lower pesticide costs contributed to the relative profitability of Bt cotton. The survey was conducted during the winter of 1996-97 by crop specialists from North Carolina State University and the University of Georgia. The findings were presented at the recent Beltwide Cotton Conference in San Diego.

Reported insecticide use was lower on Bt cotton, and growers reported a significant shift from synthetic pyrethroids to other types of insecticides on their Bt cotton, according to the survey. A random sample of Southeastern cotton growers in Alabama, Georgia, South Carolina and North Carolina were surveyed during the winter months of 1996 following the growing season. About 300 farmers completed the forms, for an acceptable response rate of 30 percent.

For the entire sample of respondents, about 22 percent of the cotton acres were planted to Bt cotton in 1996 but 36 percent of all growers planted some Bt cotton. Reported acreage adoption was much higher in the lower South (25 percent) in Georgia and 66 percent in Alabama) than in the upper South (three percent in North Carolina and 14 percent in South Carolina). Growers who adopted the new technology in 1996 experienced an 11.4 percent yield improvement on their Bt acres compared to their conventional cotton acres. Insecticide applications per season were 72 percent lower on the Bt cotton compared to the conventional cotton acres.

There also was a significant reduction in total insecticides applied with a more than proportional reduction in synthetic pyrethroids on Bt acres. Additional profits from Bt cotton averaged $51 per acre or a 155 percent return on the seed investment, according to the survey. The average yield increase on Bt cotton acreage compared to conventional acreage was not statistically significant in the upper South. However, growers in the lower South experienced a 13 percent average yield increase on their Bt cotton acres.

In both regions (upper and lower South), growers who did not adopt Bt cotton in 1996 had significantly lower yields than the conventional cotton yields of those who did adopt Bt cotton on some of their acreage. Most of this difference occurred in Georgia. This result, according to the survey, is somewhat puzzling, and further research is being conducted. Bt adopters in both regions showed a significantly lower number of insecticide applications on their Bt acres compared to their conventional acres. On average, insecticide applications dropped from two to three applications per season to one or less.

Forty-five percent of the growers made no spray applications. The average percent decrease in insecticide applications was 72 percent. Total insecticide active ingredients decreased, as well, in both regions. Growers used proportionately fewer synthetic pyrethroids on their Bt cotton acres and slightly more organophosphates. This decrease in pyrethroid use may help to slow resistance buildup to this class of insecticides in cotton, based on the survey. Combining the increased yield effects with the lower insecticide use resulted in additional net benefits to adopters over and above the additional seed cost and technology fee, according to the survey.

Average additional profit was $82 per hectare in the upper South assuming the yield increase occurred - and twice as much in the lower South or $160 per hectare. This represents a 121 percent rate of return on the extra investment in the upper South and a 174 percent rate of return in the lower South. Based on these results, states the study, Bt cotton adoption should proceed fairly rapidly in the Southeastern states, especially in the lower South. This is welcome news to cotton producers, as the better Bt cotton economics come at a time when cotton acreage is decreasing and cotton prices are declining.

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