Question

There are several herbicides available that claim to kill lawn weeds but not the lawn grass. This seems amazing, to me. How does this work? How can a chemical be lethal to a broad range of plants, but not to grass? What’s the difference between weeds and grass?

Answer 1

Selective herbicides target specific weedy species while sparing grasses, utilizing differences in plant growth hormones.

Step-by-step explanation:

Herbicides, commonly known as weedkillers, are substances designed to control unwanted plants. Selective herbicides differentiate between crops and weeds through various mechanisms, such as targeting growth hormones specific to broadleaf weeds but not grasses. An example is 2,4-D (2,4-dichlorophenoxyacetic acid), which affects broadleaf plants without harming grass.

Another approach is the development of herbicide-resistant crops, such as 'Roundup Ready Soybeans', which allow farmers to use non-selective herbicides like glyphosate to eliminate weeds while leaving the crop intact. This resistance is achieved through genetic modifications that integrate resistance traits from bacteria into the crop plants.

Concerns about herbicide use include the risk of developing herbicide-resistant 'superweeds', as well as potential health risks to humans and environmental impact. These challenges have prompted an interest in organic farming methods employing organic herbicides such as corn gluten meal or vinegar, which tend to be less effective than synthetic alternatives and often require integrated pest management strategies.