Pesticide resistant weeds are introducing a new problem to cotton
farmers. Traditionally, herbicide resistance is dealt with by
simply changing the herbicide. But according to North Carolina
State weed scientist Alan York, farmers are running out of options:
there are no more effective pesticides to switch to. The majority
of farmers in the Cotton Belt are now growing Monsanto’s genetically
engineered Roundup Ready cotton, which is resistant to glyphosate
pesticides. As a result of the heavy use of glyphosate in the
area, varieties of pigweed have developed an immunity to it. Tests
at the University of Georgia showed that the pigweed Palmer Amaranth
has developed amazing resistance to glyphosate. Scientists doused
the weeds three times with a quadruple concentrated dose of glyphosate,
but the pigweed continued to grow and multiply. "If you grow
cotton in the Southeast, and you have Palmer amaranth in your
fields, looking at side-by-side comparisons of resistant and non-resistant
pigweed should scare you to death," York says. /old_articles/ge/cotton060404.cfm