Certain herbicides (e.g., sodium arsenite) are sometimes applied by the jar method, whereby the tops of weeds are bent over and immersed in jars of poisonous solution. The herbicide is drawn into the rest of the plant and into connecting plants, gradually killing the entire system. Wild morning glory, poison oak, and camel thorn are sometimes treated in this manner. Chlorinated benzene and certain aromatic solvents are used to control aquatic weeds by adding them directly to the watery medium. See also defoliant. These genetically modified organisms (GMOs) enable effective chemical control of weeds, since only the HRC plants can survive in fields treated with the corresponding herbicide. Such crops have been especially valuable for no-till farming, which helps prevent soil erosion. However, because these crops encourage increased application of chemicals to the soil rather than decreased application, they remain controversial with regard to their environmental impact and general safety. In addition, in order to reduce the risk of selecting for herbicide-resistant weeds, farmers must use multiple diverse weed-management strategies.