My sister, who lives in the Pittsburgh area, just gave me a call. She and her husband have two kids and a lawn and she wanted to know my feelings about using herbicides to keep the grass free of weeds. When we were growing up our parents had a large lawn (and lots of fruit trees) and it took two of us two hours to mow the whole thing. It kind of turned her off to grass. The truth of the matter is that she doesn’t even want the lawn she currently has, but her husband wants it – and he wants it weed free. So she called me giving me the “you’re supposed to know about this stuff” line and asked me what she should do. My response was that the herbicide her husband would be applying (trimec) wasn’t on my list of super bad things to apply, but that, in my opinion too many people want their lawn too free of weeds. I don’t see anything wrong with applying an herbicide once a year – it won’t keep a lawn pristine, but it will knock out most of what most people want knocked out. Why do people insist on having spotless yards – applying herbicides from three to six times per lawn per year? It’s insane. Not so much for the safety of humans, but for the good of the lawn ecosystem. It’s good to have a mix of different plants – it’s healthy. Using an herbicide really cuts down on you biodiversity, and can affect the safety of dogs too. You see, 2,4 D, probably the most used pesticide on lawns in the US (and a component of trimec), isn’t rapidly excreted by dogs. If we are exposed to 2,4 D we just pee it out – our kidneys process it rapidly and out it goes. In a dog’s system this chemical sits and sits. It is for this reason that 2,4 D is considered particularly bad for dogs and is suspected of potentially causing cancer.
One more note about dogs. The reason that lawns get dog spots is because of the amount of nitrogen in the dogs urine – it kills plants – it IS NOT because of the pH of the urine.