In 1999 the cost of pesticides and the yield loss of crops to pesticide resistance was estimate at $1.5 billion in the US alone.  In 1996 it was estimated that over 500 insects were resistant to one or more pesticides commonly used to control them.  There were also 270 weed species, over 150 plant pathogens and a half-dozen species of rats that were resistant.  Those numbers have only grown in the last 15 years.

There is even a common name for this problem.  It is called the “pesticide treadmill”.  It is called a treadmill because once it starts to develop people apply more pesticide which causes more resistance.  So more pesticide is applied and even more resistance develops.

In some places in the world mosquitoes that spread malaria are resistant to all pesticides known to control them.  Pigweed, the most common weed in cotton fields is resistant to the active ingredient in the herbicide Roundup.  In Florida in 2002 somewhere between 10 and 50 sites the aquatic plant hydrilla is no longer controlled by the preferred herbicide.  This forces use of a more expensive herbicide to control it cost taxpayers more.

• You can help by applying pesticides responsibly:
• Use mechanical methods
• Use natural products
• Only use chemical pesticides as a last resort and then do spot treatments.
• Only use a pesticide that has your pest on its label.
• Find pest tolerant plants to use in your garden.
• Clean up debris and dead leaves from around plants to reduce habitat for insects.
• When mixing pesticides from concentrate; follow the directions.
• If you use chemical pesticides, rotate among a variety to as not to develop resistance.

Recently, farmers have realized that certain weeds weren’t dying anymore; in Georgia that plant is Palmer Amaranth, commonly called pigweed.  This strain of pigweed has a genetic mutation that makes it resistant to Glyphosate, the weed killing chemical in Roundup.  Thirteen states are reporting weed resistance and farmers’ associations are reporting 103 biotypes of weeds with herbicide resistance.

Glyphosate is the most used herbicide in the United States and while the chemical has been associated with deformities in a host of laboratory animals, its impact on humans remains unclear; the Environmental Protection Agency (EPA) considers glyphosate to be relatively low in toxicity, but does post the greatest danger to amphibians.  Fish and aquatic invertebrates are more sensitive to Roundup, which is not registered for aquatic uses.

Farmers are now looking for alternate solutions to manage the weeds and they are turning toward Stanley Culpepper; a weed scientist at the University of Georgia and is the state’s expert on cotton weeds, for help.  He says the days of easy weed killing are over and that farmers are going to have to spray a lot of different chemicals to overcome the weeds and some will kill their crops if care isn’t taken.  Culpepper believes that the key to surviving the herbicide resistant weeds it to try lots of different things; some involve chemicals and some doesn’t, but it will mean more work.

However, another extremely tempting solution for farmers will be a new batch of engineered crops that will be resistant to the herbicide needed to kill the pigweed.  Dow AgroSciences, Monsanto, and Bayer CropScience, three big cotton seed companies; plan to sell such a seed within the next few years.  Farmers will be able to spray 2,4-D (one of two ingredients used in the production of Agent Orange) and dicamba right over their crops like they are doing now with Roundup.  Dow Agrosciences has already asked the US Department of Agriculture to approve genetically modified corn, which will allow farmers to spray with 2,4-D.

David Mortensen, a weed ecologist at Penn State University and other environmentalists are angry about these new products.  Mortensen predicts that weeds will evolve and develop resistance to these new herbicides leading to an endless cycle of new crops and new chemicals. “When one herbicide fails, you add a second herbicide, and then a third herbicide to the package.  And I am convinced that this is not a sustainable path forward.”

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