Lawn weed & bug killers: How dangerous to humans?

[Carnac_the_Magnificent]

According to the Scotts Company, Inc., it’s time for me to apply grub killer to my lawn. AFAIK, this involves spreading some nasty equivalent of Diazanon or Dursban all over the grass. At other times, I apply a pre-emergent crabgrass killer, broadleaf killer, another late-summer application of crabgrass killer, and then there’s my ongoing battle with clover.

Most of my neighbors use lawn services, where technicians without respirators apply their chemical brew and then post lawn signs instruction kids, in tiny print, to keep off their lawn for 48 hours. (Doesn’t sound long enough to me.)

My question: Even if one keeps off his lawn for, say, 72 hours after application of weed or pest killer, doesn’t the grass absorb these chemicals?

And if this does happen, when I’m mowing my lawn, aren’t I breathing virtually aerosolized grass clippings contaminated with insecticide/pesticide?

[tanstaafl]

This isn’t answering exactly the same question but it looks like Cecil doesn’t think there is a problem.

Are “this lawn chemically treated” signs a scam?

[DeVena]

List of EPA fact sheets about pesticide use and safety.

From Assessing Health Risks from Pesticides…

Paracelsus, the Swiss physician and alchemist, the “father” of modern toxicology (1493-1541) said, “The dose makes the poison.” In other words, the amount of a substance a person is exposed to is as important as how toxic the chemical might be. For example, small doses of aspirin can be beneficial to people, but at very high doses, this common medicine can be deadly. In some individuals, even at very low doses, aspirin may be deadly.

A child would be more susceptible than an adult due to having a smaller body mass. Also pesticides are generally considered more hazardous in “application state” (as in, liquid or airborne powder). And over time, applied pesticides lose potency from being exposed to the elements (wind, dew or rain, sunlight); very little pestide would be aerosolized during normal grass cutting, providing you aren’t doing this immediately after pesticide application.

It’s also good to remember that overuse of pesticides not only hurt your lawn, it affects your environment. It’s called Non Point Source pollution.

Nonpoint source (NPS) water pollution, also known as polluted runoff, comes from diffuse or scattered sources in the environment rather than from a defined outlet such as a pipe. As water moves across and through the land it picks up and carries away natural and human-made pollutants depositing them into lakes, rivers, wetlands, coastal waters, and even our underground sources of drinking water.

[Phlosphr]

Pestacides are bad no matter what way you look at them. And why use pestacides and weed killers when you can go Organic/biological and kill all the little nasty bugs and grubs with nematodes. . That cite has everything you’ll need to take care of your problem the safe and biologic way. I’ve been using them for years and have wonderful lawn. Home Depot and Lowes carry them in quantity.

[Philster]

Don’t get me started.

Mistake 1: Let me guess. You use a lawn program or big name fertilizers. These water soluable fertilizers don’t help your lawn. And while Scotts has some other non-water soluable nitrogen in there, it still sucks.

Mistake 2: you think these are needed to have a nice lawn

3. You probably bag all your clippings.

4. You probably fertilize three or four times a year, using the weed kill, bug kill, etc with it.

5. You probably bought disease/fungus control before.

Reality… *
Fertilizer:
You can fertilize in fall and leave it at that (golf courses do). Good options are brands known as Ringer, Milorganite…and check local nurseries/garden centers because there are many locally produced organic ferts (chicken poop, fish products, etc) that are bagged and prepared. If you are using organix, you can fert in spring, too (optional)

Cutting:
Muching blade…highest setting…leave clippings…cut regulalry
You should use a mulching blade and leave the clippings.

Weeds:
If you cut properly, you won’t have weeds. A few. This is incredibly hard to believe, but easy to understand: high grass shades seed, it won’t germinate. Healthy grass suffocate weeds. Clippings feed the grass and block sunlight from weed seeds. it’s a cylce…the best things in nature work on a cycle.

Bugs:
Healthy lawns tolerate bugs. When you get off the drugs (big name ferts & chems), you will have a lawn that has good and bad critters, and they keep eachother in check.

Disease:
Do you love diseases? Fungus? Mysterious lawn problems!? You do!? Then load up on all those big name fertlizers and other chemicals! You are** living ** now! Run out now and buy the disease/fungus control they sell (coincidence?)! Get your lawn off drugs and kiss disease good bye. And, using fungus/disease control causes long term harm for short term results. Oh, tall grass 3-4" can take a hit, like a healthy person can get to work with the sniffles. No sweat.

Watering;
HEAVY, 2-3 per week…DEEP. In morning.

Why does this all work? One thing helps the other. Proper mowing prevents thatch (which reduces disease…whick makes a healthier lawn…which chokes weeds. Reduced chem ferts reduce thatch…which reduces disease…which makes a helthier lawn…etc…Proper watering reduces thatch, etc…organic ferts prevent thatch, etc…clippings supply free fertilizer, they shade the soil, which saves water, which reduces thatch, weeds. Healthy chem free lawns grow slowly, which recudes watering, etc…Chem free lawns have good critters (worms)…I could go on for hours!

I simply have the easiest, cheapest, lawn around. I fertilize one or twice a year with Ringer organic, and resist any temptation to use bug or weed killer. And if you want, like others said, there are chem free options for that. If you have 3-4" grass, it’s hard for bugs or disease to eat the individual plants out of blade and root. Chances are, each grass plant has enough substance to make it. If you buzz cut the grass to 2", the roots and blades are short and can be gobbled up twice as fast…actually more than twice as fast, because they are unhealthy and not drought resistant either…and weeds are probably around too!

You need not underestimate the power of the above suggestions. Each one has a huge impact and plays a key role in keeping your pocket and lawn green.

I shake my head and laugh at all my neighbors. That is the best reward.

[Finagle]

@Philster

Don’t get me started.

Weeds:
If you cut properly, you won’t have weeds. A few. This is incredibly hard to believe, but easy to understand: high grass shades seed, it won’t germinate. Healthy grass suffocate weeds. Clippings feed the grass and block sunlight from weed seeds. it’s a cylce…the best things in nature work on a cycle.

Bugs:
Healthy lawns tolerate bugs. When you get off the drugs (big name ferts & chems), you will have a lawn that has good and bad critters, and they keep eachother in check.

This seems contrary to my experience. Certainly crab grass (which I would classify as a weed) doesn’t care how thick my lawn is, or how tall. And while a healthy lawn might tolerate bugs (again, not in my experience), a stretch of hot or overly moist weather can stress a lawn, opening up the gate for disease.

I’m a bit inclined to think that there is a happy medium between the weed-and-feed using the products of the evil agri-monopolies and your organic philosophy.

[Philster]

Crab grass: Tougher to control, yes. In areas where my lawn is tall, healthy and thick, it rarely rears it’s head. It weaker areas (my back) that suffer under large oak trees and heavy clay soil, it does appear.

Certainly, there is total organic psychosis, in which clover becomes a permanent part of your lawn, and areas of crab grass don’t worry you, and there is a happy medium , where you apply an occassional chemical as needed, and in certain areas. Absolutely a far stretch from 4-5 step program, plus weed control, bug control etc over the whole lawn blindly.

The thing I mentioned stack the odds in your lawns favor, but you can just dabble in the use of chems as needed.

Even nice golf courses have a friendly patch of clover or crab grass here and there. And if you practice good lawn care with good cultivation habits, you’ll find you need only to spot control, as oppossed to a landfill of chems that run off to poison to the local water shed.

[ftg]

Diazanon is one of the nastier chems out there. I would never allow anyone to broadcast it over a large area of my lawn. Spot treatment max. But note that it is actually a grass killer in moderate doses!

The Really Nasty Stuff to avoid are fungicides.

As for The Crabgrass Issue: When I first moved here I had crabgrass in my lawn. Now I don’t. No chems were used at all. Nor did I hand weed. I also don’t have thick grass due to a lot of trees. Just basic common sense lawn care. I.e., keep the lawn healthy (which means keep the chems to a min.).

[Philster]

Crab grass loves sucky soil.

Use chem fertilizers/urea based nitrogen/water soluable fertilizer and poor cultivation habits (like bagging the free organic matter called clippings) and you are killing the soil.

Crabgrass, weeds, disease, moss, chickweed and numerous others love sucky soil.

No problem. Big Chemco sells weed killer. Convenient.

To directly answer the OP: The chems, even basic fertilizer from ChemCo, are dangerous to humans because they contaminate the local water supply…esp local water sheds.

Broad use of these products almost gaurantees runoff into local water and will adversely affect local fish and animals. This is not good for humans.

[Stan_Doubt]

I’ve never worked with turf specifically, but have applied/sprayed a variety of pesticides in agriculture.

In these situations, I was always given the opportunity to have pre- and mid- season (cholinesterase activity) bloodwork done to help my doctor and I decide whether I was at risk from various pesticides I was exposed to. Because many pesticides, such as Diazinon, Malathion, Chlorpyrifos, etc. work as neurotoxins, and disrupt the normal biological cycle of a neurotransmitter called acetylcholine, this test can give a good idea of one’s exposure to these chemicals.

Here is a link to a California EPA document on the subject, intended for physycians who are caring for or supervising agricultural workers:

http://www.oehha.ca.gov/pesticides/pdf/docguide2002.pdf

While the chemistry is complicated, suffice it to say that acetylcholine is used and normally “recycled” very quickly at the site where a neuron (brain cell) and muscle fiber interact. A family of enzymes called cholinesterases allow the neurotransmitter to “un-bind” and the muscle to ready itself to work again. Many pesticides work by inhibiting the action of cholinesterases.

Again, I have zero experience with turf crops, or granular/pelletized formulations in general, but I would assume that pelletized formulations typically used in lawns would tend to be much less risky than liquid or powder spray formulations.

Pesticide regulations may vary by state and municipality, but they are intended to prevent incidental contact after a pesticide application, and give Re-entry intervals (REIs) for various pesticides. The sign on your neighbor’s lawn is intended to keep people away from the chemical when it is believed to be most harmful.

IMHO, the exposure you (the OP) would experience by mowing your lawn (as directed) following a routine pesticide treatment would be insignificant, and your exposure mowing the lawn after a subsequent rain event would be unmeasurable. You are simply much larger than an insect larva and it would take a much larger exposure to cause you any harm.

This post is not intended as an endorsement of the use of pesticides in lawns, simply an answer to the OP. As others have pointed out, there are serious disadvantages to the widespread use of nonspecific insecticides. Incidental human exposure due to lawnmowing is not, however, IMHO, a valid concern.

[bsane]

@Phlosphr

Pestacides are bad no matter what way you look at them.

You mean for your lawn right? Because that would be a bold and GD worthy statement otherwise.

[Phlosphr]

@bsane

You mean for your lawn right? Because that would be a bold and GD worthy statement otherwise.

I’d go to GD with my statement, but I’m not in the mood today! I don’t like pesticides at all. At all. That said, I’m not a tree-hugg’in green peace vegan either, and some spot treatment, and horticultural uses are fine in my book.

Oh and as usual I second what Philster Said, especially the part about the mulching blade and high cut

[bsane]

@Phlosphr

some spot treatment, and horticultural uses are fine in my book.

No worries… It just sounded like you were a tree-hugg’in green peace vegan who thinks that pesticides should have never been invented/discovered, but since your not…

Obviously there could be a lot of rational discussion about using them too much or for the wrong thing, but they can be a very safe and effective tool.