Will this weed killer hurt my grass?

Alex's lawn was overrun with dandelions and crabgrass, so he decided to buy an herbicide to kill the unwanted plants. At the store, he found many weed killers to choose from. The product that caught his eye was a "complete" weed killer that featured pictures of his weeds on the label. Alex purchased the product, mixed it according to the instructions while wearing gloves and applied it thoroughly to the weedy spots in his lawn and pavement cracks. Several days later, he noticed with satisfaction that the weeds in the sidewalk cracks began to wilt. However, brown patches in his lawn began to appear as well, especially where he had focused his weed control efforts. Alex realized with dismay what he may have done, and called the phone number on the herbicide label.

Take Home Message

The NPIC pesticide specialist explained that some products are selective and kill plants such as dandelions OR crabgrass, and leave other plants, like grass, unharmed. The specialist said there are other products that are designed to kill all plants (non-selective herbicide). Alex had purchased and used a non-selective herbicide by mistake.

Alex asked if his lawn would recover if he re-seeded the area. The specialist said herbicides can work as pre-emergent, and/or post-emergent pesticides. Pre-emergent herbicides keep weed seeds from sprouting, whereas post-emergent herbicides kill weeds that are visible. He went on to say that if Alex's product has pre-emergent herbicidal activity, grass seed may not be able to grow in those areas for an entire season, or longer!

Alex regretted that his seemingly small oversight may have cost him his beautiful lawn for an entire summer. He learned to read the entire product label from now on and call NPIC if anything on the label is unclear BEFORE using the product.