I put down an application of Scotts plus Halts for crabgrass every spring. My lawn looks great until the end of July – then I start to notice patches of crabgrass returning. Can I use it again during the season?
– Mr Nicelawn
Sure, right. Bossy knows the very product you’re talking about. It contains 27% Nitrogen, 3% Phosphorous, 4% Potassium, and 0.194% Dithiopyr. Don’t know what Dithiopyr is? Understandable. You’re probably more familiar with its Common name: Dithiopyr.
According to the EPA, this is a very safe chemical. Of course they’re still awaiting a little item they like to call ‘weight-of-the-evidence summary assessment’. Just means they’re still missing data typically compiled by a panel of experts who look for certain types of toxicity – just little stuff such as cancer, birth defects, and reproductive harm.
We do know that Dithiopyr is toxic to Sheepshead Minnows, Bluegills, and Donaldson trout – as well as various mollusks, phytoplankton, zooplankton, and water fleas (OK, we’re not too sad about the water fleas.)
We also know that when applied topically to the shaved backs of New Zealand albino rabbits, it resulted in erythema. In layman’s terms, that’s an acute mucocutaneous hypersensitivity reaction of variable severity characterized by a symmetrically distributed skin eruption. You know, blotchy skin.
We also know that when eye-dropped into the conjunctival sac of albino rabbits, eye irritation was observed. These albino rabbits have all the luck.
But that doesn’t begin to detail what happened to the thirty-six mice and thirty-six rats that were fed Dithiopyr and died from liver, kidney, and thyroid diseases. Disregard the EPA warning that Humans are not necessarily similar to rats. But whoever said that never met any Hollywood executives.
So, sure, Mr. Nice, you can reapply your vile chemical in July, but only when the crabgrass is in the one to three leaf stage – beyond that stage you’ll kill all surrounding plant and animal life — but your crabgrass will survive.