• Herbicide-resistant crops allow you to attack the weeds without hurting the crop.Jupiterimages/Photos.com/Getty Images
  
  Herbicide-resistant or genetically modified organism (GMO) crops are genetically modified so that the crops are not affected by herbicides and pesticides. This allows farmers to spray weed-killing herbicides without adversely affecting the crop even during the sensitive stages. According to GMO Compass, herbicide-resistant crops degrade the active herbicide ingredient, making it harmless to the crop. This site, however, states that there is controversy surrounding the use of GMOs, since they can reduce the number of wild plants on a farm.
  
  

Soybean

• According to Pennsylvania State University, there are two main types of herbicide-resistant soybean varieties: Roundup Ready and LibertyLink. The Roundup Ready soybean is resistant to herbicides from seed cracking through to flowering. This allows farmers to use Roundup and similar herbicides that use glyphosate anytime. Glyphosate is an herbicide used to kill broadleaf weeds and perennial grasses. LibertyLink helps farmers deal with broadleaf weeds and grasses using glufosinate, which is an active herbicide ingredient in Ignite 280 herbicide. Both types of soybean varieties allow you to add multiple coatings of herbicides.
  
  

Corn

• There are three main varieties of herbicide-resistant corn, according to Pennsylvania State University. Roundup Ready corn allows you to use glyphosate herbicides on your corn, including Roundup weed killers. ClearField corn is resistant to imidazolinone, which is an active ingredient in Scepter and Pursuit herbicides. This is a hybrid corn, which means that it was created by preserving the best traits of different types of corn. Additional varieties of the ClearField hybrid are also resistant to sulfonamide, which is found in Python herbicide, and sulfonylurea, which is found in Exceed and Accent herbicides. LibertyLink corn is genetically engineered to make it resistant to glufosinate, which is found in Liberty herbicide products.
  
  

Cotton

• According to the Farrer Centre, genetically engineered cotton is resistant to glyphosate (Roundup Ready) and glufosinate (LibertyLink) herbicides. Other varieties are also resistant to bromoxynil and 2,4-Dichlorophenoxyacetic acid (2,4-D). Bromoxynil is a pesticide used for the control of annual broadleaf weeds, and you apply it after these plants have emerged. This is a restricted-use pesticide (RUP), which means that homeowners cannot use this product. According to Extonet, 2,4-D is an ingredient in different herbicides, including Plantguard, Weedtrine II and Crop Care's Barrage Herbicide.