By Vershal Hogan
A recently published study suggests that bollworms are developing a
resistance to a common pest control method.
Bt-cotton is a genetically engineered plant that produces the toxin
Bacillus thuringiensis, which is deadly to several cotton pests.

After analyzing tests from Australia, China, Spain and the United
States, University of Arizona researcher Bruce Tabashnik concluded that the
American cotton bollworm ? or, scientifically, Helicoverpa zea ? has begun
to evolve a resistance to the toxin as it exists in the genetically
engineered cotton.

Some of the plots where Tabashnik said bt-resistant bollworms were
observed were in Mississippi.

There?s no reason to panic if the bollworms have developed the
resistance, Tabashnik said.

?There are other control methods for bollworms such as conventional
pesticides,? he said.

The problem is that the engineered plants were developed to ease the
use of pesticides.

?The reason these plants were developed was to reduce the use of
pesticides, but that?s not an area of major concern,? Tabashnik said.

For Concordia Parish farmer Buddy Tanner, who has used the engineered
cotton since it first became available approximately 12 years ago, there?s
not a lot of concern about the bt-resistant bollworms at this point.

?They?re still a good distance away,? Tanner said.

And Tanner said if the bt-resistant bollworms made their way into the
area he would just have to use more pesticides.

?We?re trying to move away from that because pesticides are expensive
and can be harmful to the environment,? Tanner said.

MSU-cotton entomologist Angus Catchot said he has not yet encountered
the bt-resistance at a field level, and even Tabashnik noted in his research
that some researchers thought that a low susceptibility to the bt-cotton was
just a natural variance within the bollworm population.

?The bt-cotton has never been that good at controlling the bollworms
at the reproductive stage anyway,? Catchot said.

But if the caterpillars are developing a resistance to the toxin,
other major pests it targets are not.

?There are five other major pests that are not showing any resistance
(to the bt-cotton),? Tabashnik said.

The bollworm ? also commonly known as the corn earworm and the tomato
fruitworm ? is a caterpillar that consumes cotton bolls. As an adult,
Helicoverpa zea is a moth.


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