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Lawn Sharks
12-01-2002, 11:40 AM
Found an interesting study of which I pasted a section below. This is not meant to incite a riot but instead to provide interesting reading for those considering organic additions to their current service. A lot has been said, in the archives, about organic vs. inorganic fertilzers and pesticides but very little mention of the benefits and/or harm to the long term health of the organisms that already live there. It is a fascinating compilation of different studies. For the whole document go to :

http://www.cityofseattle.net/util/lawncare/docs/Grnlwn61.pdf

Here is a small segment that I found particularly interesting......

"Ecologically Sound Lawn Care for the Pacific Northwest Why Make A Change? 10
.......Earthworms and other soil invertebrates are essential to maintaining soil structure and recycling organic
debris, such as thatch, back into nutrients available to the grass plant.85 86 87 Thousands of microorganism
species (bacteria, fungi, and protozoa) form the food base for these invertebrates.a The microorganisms
perform the essential first steps in nutrient recycling, and build soil structure at the microscopic level.88 89
They also compete with and (along with predacious invertebrates) prey upon the relatively few fungi and
insects that cause pest problems in turfgrass.90 91 Several studies have identified negative side-effects of
regular use of pesticides and soluble fertilizers on the health of this soil ecosystem, and on turfgrass vigor,
drought hardiness, soil compaction, and thatch buildup.
A study measuring acute toxicity to worms concluded that most pesticides were “very toxic to extremely
toxic” (LC50 = 1-100 mg/cm2, which means that at that concentration half the earthworms died during a
short experiment) and reported that the breakdown products of 2,4-D were more toxic than the original
material. The soluble fertilizers that were tested, ammonium nitrate and methyl urea, had LC50’s in the
100-1000 mg/cm2 range.92 Another study concluded that earthworm growth and reproduction is
significantly reduced at much lower chemical concentrations than those that cause death.93 Several
turfgrass trial studies with commonly used fungicides, insecticides and herbicides have reported large
reductions in earthworm activity and a significant buildup of thatch layers, compared to untreated control
plots.94 95 96 97 98 Another study reported that mechanical exclusion of earthworms (by mesh bags)
prevented thatch breakdown, and concluded that earthworm activity provides benefits (such as soil
incorporation into the thatch layer) that are comparable to topdressing with topsoil.99
A trial that simulated a high-maintenance (synthetic fertilizer, herbicides and insecticides) lawn care
program for four years concluded that “soil and thatch pH decreased significantly [soil became more acid]
and thatch accumulation more than tripled under the high maintenance program” compared to untreated
control plots. Soluble nitrogen fertilization commonly results in soil acidification, which inhibits microbial
activity and soil invertebrate populations.100 A seven-year trial of varying rates of ammonium nitrate
fertilization on turf reported that soil acidity and thatch thickness increased, and earthworm and other
invertebrate populations decreased, in direct proportion to increasingly high levels of nitrogen
fertilization.101
Soil compaction, like thatch buildup, causes poor root development, lack of drought hardiness, and lack of
vigor in grass plants.102 A trial on British sports fields where worms were killed with a strong insecticide
reported that water infiltration rates fell 16% by six months after treatment, and fell 40% by twelve
months after the worms were killed. This study concluded that “The main cause of the reduction was
a Dr. Elaine Ingham of Oregon State University notes, “Earthworms do not make the enzymes to degrade organic
matter – they have the enzymes to digest bacteria and fungi and absorb the soluble nutrients that are released.
Bacteria bind the smallest building blocks of soil into microaggregates. Fungi, and root hairs, bind the small building
blocks into larger aggregates. Earthworms consume these aggregates, with the bacteria, fungi, root hairs, protozoa,
nematodes and arthropods in them. Earthworms then build larger channels in soil, but the smaller aggregates and
other organisms must be present for earthworms to survive in soil.”
blockage of the main conducting channels,” as these large pore spaces were no longer being created by
the earthworms.103 In a laboratory experiment, researchers concluded that the presence of earthworms
“greatly enhanced” the growth of perennial ryegrass. “Uptake of most major and trace elements by
ryegrass was increased in the presence of earthworms.” That study also concluded that earthworms
reduced soil compaction and increased pore space in the root zone of the ryegrass plants.104
Most plants, including grasses, depend on webs of beneficial fungi, which grow in and around their root
systems, to provide both nutrients from the soil and protection from disease-causing fungi.105 Several
studies have concluded that these beneficial “mycorrhizal” fungi (“root-fungi”) are inhibited by fungicides,
and also by high levels of fertilization.106 107 108
Resurgence of disease and insect problems is commonly reported after use of fungicides and insecticides,
because of reductions in fungi and insects that compete with or prey upon the problem pests.109
Resistance to pesticides developed by both insects and fungal diseases is also commonly noted by turf
scientists and professionals.110
The scientific literature reviewed here suggests that turf management techniques that support the diversity
of life in the soil community, through proper cultural practices and through limiting the intensity and
frequency of chemical applications, will yield healthier turf with less thatch and fewer soil compaction,
disease, and insect problems."

KLR
12-03-2002, 08:31 AM
Keith, i'm curious, what do you apply for weed control, disease control, insect control??

i'm also curious why you use the term 'organic', instead of 'natural'?

interested in having an open minded, unemotional conversation concering 'organic' vs 'chemical'

Lawn Sharks
12-03-2002, 09:09 AM
I use the word "organic" strictly for marketing purposes and have only recently added it to my flyers and brochures but have been practicing these principals for awhile now.
"Organic' is a hot word right now with the higher end clients as they are all buying organic vegetables etc. These people pay a premium of about 15-20% to eat vegetables that were grown organically.
This helps a great deal when informing them of pre emergent and fertilizer costs.

As for pesticides, herbicides and fertilizers I use very little. Just as a person who buys organic celery may expect to see a worm tucked in between the stalks I educate my customers that a lawn with a small percentage of broadleaf weeds still looks good from the street and it is child-safe. Once I get the lawn in shape after years of abuse from fast release nitro products they are shocked at how good it looks.

Fertilizer Program - Aerate, topdress with Grade A compost. For a quicker boost I use alfalfa meal which is about 3-2-2. Not very effective in colder weather but, again, I educate my customers about it. I use a bit of lime as well where needed. Mow to 2 3/4 -3 1/4 inches.

Weed Control- Typically don't use any herbicides as a healthy well overseeded lawn will choke out most weeds. If you have a lot of weeds there is something wrong with the soil. "Feed the soil, not the plant" Will use corn gluten meal for bad cases of crabgrass applied in spring when the forsythias bloom to recover a lawn that I just took over. I walk a yard with a bag and do spot removal of some weeds by hand if they have taken over an area. Again, aerate, compost, overseed and watch the grass choke out most weeds. Nothing wrong with clover although it may be a sign of soil in need of help.It usually decreases dramatically after aeration and compost dressing. For driveways and sidewalk cracks I use a mixture of acetic acid (pickling vinegar), orange oil and a bit of soap to help it stick. Doesn't work on everything but it is quite effective.

Pesticides- None that I use on a regular basis. Have tried different things in rare cases but my first priority is increasing the health of the soil. Once this is accomplished pests are typically not a problem. I have never had army worms though! I wouldn't panic if it happened since the grass grows back after an army worm invasion. Around here the biggest bug problem is Japanese Beetle grubs. Nematode innouculation (short term) and milky spore (long term) are both very effective. Healthy soil contains enough balance so that grubs stay in check. Again, the soil is the key.

I have nothing against those who choose to apply chemicals and run around with bottles of Roundup it is just that I choose not to do it myself. I, romantically, see myself as a caretaker of soil and am pleased when I can look at a lawn that I have been caring for and know that the soil is alive and taking care of itself with a little help from me.

My way takes a bit longer and I charge for it.

Hope this helps.

Keth

KLR
12-03-2002, 11:46 AM
i agree that 'organic' is a huge "buzz" word. funny, how most people dont have a clue as to what it means. we have folks ask us if we are 'organic', i say we have a synthetic organic fert. product as are basic service and can provide a 'natural' product at a higher cost.

i also agree that the best weed control is a thick turf, and i agree that people need not freak out over insect populations. if they understand thresholds. we get tons of calls from folks who use a mowing service and that guy tells them they have 'bugs'! Or the irrigation guy who, during his install, sees a couple of grubs and tells homeowner they are going to loose their whole lawn!

we dont get involved with vegitation control in cracks on driveways/sidewalks, we'll tell homeowner to have their mowing guys take care of it (most will beat it down with a string trimmer now and again) if they dont use a mowing service we suggest that they could hire a neighborhood kid to handle it.

aeration is the best thing anybody could do for their lawn, no matter what condition it is in.

we have never used milky spore or nematodes for grub control (i take that back, i have used milky spore years ago when i worked for another company) found little to no results. was told that we are to far north, yet you are further north then us, go figure.

the corn gluten is another product that we have not used yet, but i also here very limited control over crabgrass.

though we practice IPM, we do blanket pre emergent crabgrass controls, spot treat broadleaf weeds when needed and we use Merit for grub preventative control. so, as you can see, we are not totally IPM. funny how many people are concerned about the planet yet expect nothing less than perfection on their properties.

we dont use fungicides. we find the majority of turf disease is from improper cultural practices. poor watering (over watering), poor mowing freqentcy and/or height. so we try to educate homeowner. of course weather patterns cant be helped, but as you know, in new england you just need wait a minute and weather will change.

we did have a huge army worm population in 2001, first time ever here in eastern MA, phone ringing off the hook, we actually stopped answering. sent out a letter to our customer base to explain that we would be out to fertilize on our regular schedule and they should water to help turf recover, not one lawn needed overseeding due to army worm. no populations reported this season, whew!

so, i feel we are on the right track, we have decreased pesticide use dramaticly over the years. i still feel there is a need for pesticides in lawn care and we use them responsablly.

thanks for the conversation

Lawn Sharks
12-03-2002, 04:22 PM
Interesting. Similar approaches.

As far as milky spore I have to add that you need to do a lot of yards in the same area for it to be truly effective according to most published literature. Seems like the critters migrate from neigbors yards.

I am unaware of any research that indicates Milky Spore is affected by freezing or that they are not suitable for this area.
I will dig around and if I find anything I will ask my local garden supply to stop carrrying it. When I bought my house we had a bad grub problem with massive amounts of Beetles in the garden after hatching so my neighbor and I did the spores for both yards since we are surounded by woodlands. We now see very few beetles and I can't remember the last time I saw a grub and always attirbuted it to the spores. Perhaps it was just improving the soil that caused the change. I think there is a way to detect by eye if a grub is infected with the spores. I will dig up the id for it.

A flock of starlings may be your best friend. It may be a wivestale but I recently that they can hear the grubs under ground and
dig em up. Always wondered what they were after when the swarmed a yard. Let's hope it is true.

Cheers,
Keth

KLR
12-03-2002, 06:25 PM
it is true that birds, starlings, black birds, crows etc. can here grub movement in soil. Also skunks have this keen sence of hearing. Thats why them rascals know exactly where to dig, natures way of survival.

getting back to milky spore. i'm under the impression that they can't survive in frozen soil conditions...got some liturature somewhere, i'll dig around this weekend. what you mentioned about doing many yards in a neighborhood makes sence, could be why i hadn't seen great results in the past.

i'm also curious about grub species, do they only affect Jap. Beetle larvae? or are Oriental beetles, northern chafers, asian beetles also controlled? last several years we have seen a decline in jap. Beetle populations, however, oriental, and northern chafers are on the rise! interesting stuff, keeps us on our toes.
have a good night

Lawn Sharks
12-03-2002, 06:58 PM
KLR,
Found a few things.

" If the conditions are right, grub population high and feeding vigorously, and soil is at least 70 degrees F and very moist, the disease can spread through the grub population in a week or two. In general, however, the disease should not be thought of as a quick knockdown insecticide. It may take a season or two before it has a substantial impact. It can remain effective for a decade."

from

http://www.beyondpesticides.org/infoservices/pesticidefactsheets/leasttoxic/microbebasedpesticides.htm

and this

The bacterium first infects a small percentage of the population and slowly kills the grubs, but two to three years are required to allow the levels of bacteria to increase among the grub population before significant control is obtained. In the meantime, other insecticides cannot be used to kill the grubs as this will prevent the bacteria from multiplying. A new Bacillus thuringiensis (Bt) strain, Bt japonensis strain Buibui, provides good control of Japanese beetle and green June beetle grubs, although it is less effective on May beetle grubs."

from

http://ipcm.wisc.edu/programs/school/section_3/whgrub.htm

Interesting stuff. Have to run install a friends computer. Back later.

K

tremor
12-03-2002, 08:16 PM
Milky Spore is only effective on Jap Beatles.
Around here chafers, orientals, & asiatics are all more common. Possibly because MS was used for many years. At any rate with the "organic displacemt" of Jap's, others have stepped up to the plate & now rule the roost. And there is currently nothing natural or organic the controls these others. Except for Skunks & Crows. They both do a nice job of controlling grubs & aerating at the same time. Cheaper too.

Steve

KLR
12-03-2002, 08:54 PM
Steve,
our customers who insist on our Natural Program (i use the word 'insist' because i dont push it) will have grub problems. typically we do a curative with dylox, not a hard sell when lawn is being torn up from preditors.

we'll go with Mach 2 on a customers property who 'insist' on our natural program as a preventative. explaining to customer how mach 2 works, affecting molting of larvae, it also is not a hard sell. of course, poor control on....hmmm....chafers?? or is it orientals?? anyway, Merit is our product of choice. even this season with the drought conditions (knowing not all customers will follow instructions and water product in) we had great control. only had one call back on a property where Merit was applied, and I'd say it was applicator error, not product failure.

i will say this about Mach 2, it claims it will stop the preditors from tearing up turf once applied. we have used it as a curative (poor results on controlling grubs) but good results on stopping preditors.

tremor
12-04-2002, 08:57 AM
My reply was in jest. But when animals do dig up turf looking for grubs, it may take a while for them to stop looking no matter what was applied.
Spraying a patch of grub infested turf with bird shot would result in very fast grub control! But skunks will still detect & try to feed on the protein until it has become more energy spent to find the insect protein than can be consumed. Sometimes animal repelents are in order for very stubborn critters. Miller's Hot Sauce works.

Mach2 is a very grub specific compound that will not impact earthworms when applied properly. It is consistant up to the 2nd instar only. Beyond 2nd instar, it won't work. So don't try. To control existing grubs with Merit, you would have to smack the 2nd instar grubs with the Merit bag to kill them, so Mach2 is more useful late season (August).
Mach2 was originally promoted at rates of 1.5lbs Ai/A. Forget that rate if you enccounter European chafers. 2.0 lbs AI/A is mandatory for EuChafers.
Milky Spore doesn't have any impact on EuChafers. To insure consistant performance of grub control, check with your local commercial friendly entomologist or chemical distributor for halofenozide rate advice before making the decision to use it. Recent cost reductions make Mach2 competitive with Merit even at the heavier rate. But if all you encounter is JapBet grubs, then 1.5# is OK.

There is a new Milky Spore Disease that will be specific to Masked Chafers, but it's not yet comercially available as far as I know. I don't know the name. Given the track record, I doubt we'll see Bayer, Dow, Monsanto, et al, lining up to purchase, register, & market this stuff. The demand would be way too low to justify the cost. And let's face it. The average LCO doesn't have the time or the client expectation to inspect every grub out break, & then treat with a species selective material.

I find the earthworm data here rather interesting. I often use urea or ammonium nitrate (depends on the temperature) in my compost pile when the green matter is low (like now), to keep the pile "cooking". I have yet to note a reduction in earthworm activity post treatment. Now sulfur containing fertilizers can impact earthworms when applied at high rates. Due most likely to rapid, short-term acidification. This is good for turf sometimes (summer patch disease) and obviously bad for earthworms. But if they recover in a timely fasion, then who cares? I am going to research these claims a little more as time allows & check back in on this.

Quite a few pesticides over the years have been noted to cause earthworm population reductions however short termed (Sevin, Benomyl, etc). Remember Cholrdane? But newer molecules aren't likely to be reason for concern. I'll check around.

If a lawn is lacking earthworms, I would first look to a soil test. Check for "Percent Organic Matter". If lower than 5%, I'd begin to periodically topdress with Peatmoss, composted manure, or quality municipal leaf compost. Then buy some night crawlers from a bait shop & release them on a cool evening following a good rain. Thatch reduction, improved fertilizer response, & enhanced water percolation are just some of the advantages.

All4now

Steve

Lawn Sharks
12-04-2002, 09:16 AM
Steve,
Thanks for the insight. Do you know why the Bacillus popillae bacterium would only choose Japanese Beetles? I know Mother Nature works this way sometimes but I would have to think, since you indicate they have developed a host specific strain of Milky disease for attacking Masked Chafers (Cyclocephala borealis), we might not be far away from a broadbased "All Grub Milky Spore". If it were developed it might be commercially viable for whatever chemical company get's the patent on it.

Thanks

Lawn Sharks
12-04-2002, 09:24 AM
http://ohioline.osu.edu/hyg-fact/2000/images/2505_2.jpg
Northern Masked Chafer Life Cycle

tremor
12-04-2002, 10:51 AM
Hi Keth,

Bacteria are some of the oldest & simplest single celled organisms on this plant. As simple as they are, their existence is still being explored. Some cause death of higher organisms like us. Others live in us & help us to digest our meals. My favorites are used to ferment spirits & ales :oD

I would have to imagine that the Jap Beatles enzymatic body chemistry contains a compound that is vitally significant to the milky spore bacterium. Indeed, when a deviant variation in milky spore cultivation took place in the '80's, the resulting version had no impact even on Japbets. Please see the following.

http://www.ag.uiuc.edu/cespubs/hyg/html/200120b.html

This is a cute explaination of soil bacteria for children. Sorry, I couldn't resist.

http://www.agry.purdue.edu/pub/bobbact.htm

You can kill some bacteria with cool temperatures or even warm water. Hydrogen peroxide, rubbing alcohol, & sophisticated antibiotics are all used to battle harmful bacteria like E-Coli & Salmonella, while at the same time, a fair part of the worlds population would starve in a matter of weeks without yeast. Others, like my Lyme Disease casusal pathogen Borrelia buradorferi, sometimes hide in the human body effectively enough to resist 6 weeks of IV antibiotic (Rosephin) therapy. ;>(

I think it remains to be seen if a volatile environment like that found in soil can sustane a stable enough bacteria population with the genetic potential to cause significant population control of a wide range of insect species. Bio engineering of specific bacteria is just getting started. Some are allready cleaning up oil spills. Yet those that clean up the Exxon Valdeez won't work on the #2 home heating oil that get's spilled on your customer's lawn. And these are even different from the bacteria that live in the fuel tank & filter of your favorite diesel dump truck.

Time will tell. I'd wager that much better options are going to arrive before guys our age are ready to retire.

Steve

GroundKprs
12-04-2002, 12:59 PM
"Do you know why the Bacillus popillae bacterium would only choose Japanese Beetles?"

Get down and dirty, get into nature, and you will find that nature is very picky. Many know that lady bird beetles (ladybugs) are predators of many harmful ornamental insects. But how many know that there are hundreds of varieties of lady bird beetles? And some varieties are very specific in their diets: they only feed on a certain instar of special insects.

So it would be likely that a disease, bacterium, or virus were also species specific on the life forms it attacks. Most of the silver bullets in the trade have been manmade, and they were often found to do damage to beneficials once they were put into general use. Predators are often larger than their targets, therefore they are easier targets for a pesticide spray - so you kill all the predators and only 95% of the harmfuls, gauranteeing a new explosion of harmfuls.

"Organic" lawn care uses naturally occuring materials, but overuse of any material can cause damage if not done properly. A bowl of chocolate is generally more harmful to a dog than a bowl of 2,4-D (dependant on concentrations of both items).

Also when using existing life forms in controls, you need to be aware that any life form requires sustenance to survive. Just because ladybugs controlled your aphids two weeks ago, you cannot assume that they will control aphids on your site forever. If the ladybugs ate all the aphids, there is no more food for them there, and they will leave and not lay eggs on your site. So next outbreak of aphids has no natural predators nearby, and their population will explode. Same idea with any natural controls. If there is no presence of the target species, the predator species or parasitic species will also decline in population. No food, no survival. True natural controls are an ebb and flow situation. As the harmful increases, the beneficial follows, reducing harmful population. But then the beneficial population decreases, letting the harmful increase again. True natural control requires a degree of tolerance.

Russ
12-05-2002, 08:36 AM
Very good thread with well thought out quality replies. Threads like this are why I come here.

f350
12-05-2002, 11:14 AM
jim, this is a really great insite..

"Organic" lawn care uses naturally occuring materials, but overuse of any material can cause damage if not done properly. A bowl of chocolate is generally more harmful to a dog than a bowl of 2,4-D (dependant on concentrations of both items)."

i really need to remember that
jonathan

tremor
12-05-2002, 05:14 PM
Here's another ugly toxicity association.

Years ago when I worked for "the Big Guys", we had a "concerned customer" leave behind peice. It explained the toxicity of a round 1 monster mix application (1lb of Urea N, 1.5lbs Ai Pre-M, Triclopyr, MCPP, dicamba, & Dursban). The application was made in enough water to deliver 4 gals H2O per 1000. Immediately after our spray residue was dry, if you mowed the lawn & collected the clippings, you would have to eat ? bowls full of clippings to equal the toxicity of 1 cup of coffee or soda (the caffiene) or 2 asprins (almost as bad as the caffiene).

I'm sorry I don't remember how many bowls of treated clipping were claimed. The idea was that anyone eating this much raw grass roughage would get violently ill & begin vomitting long before the pesticide consumed would equal the relative toxicity of a cup of coffee. I kept a few of those but have since gave them away or lost them. Maybe another old Chemmer will remember.

I did find a chart with some relative information you guys may find useful.

Material.......Oral LD50.......Pounds needed to kill 150lb man
Arsenic___________1____________________.00015 lbs
Red paintpigment__10_____________________.0015 lbs.
Iodine___________14____________________.00195 lbs.
Thiodan__________18______________________.003 lbs.
Kerosene_________28_____________________.0039 lbs.
Rotenone liquid___60______________________.009 lbs.
Lindane__________76______________________.011 lbs.
Sodium Nitrate___85______________________.013 lbs.
Windex cleaner__350_______________________.04 lbs.
Table Salt______3000_______________________.41 lbs.
Merit 75WSP____4820_______________________.72 lbs.
Heritage_______5000_______________________.75 lbs.

Kind of interesting.

Steve

KLR
12-05-2002, 06:19 PM
Steve,
as i remember from 20 years back when i worked for that large national co, chem****, pretty sure it was 50 cups of grass clippings= toxicity of 2 childrens asprin, for that application you mentioned

Lawn Sharks
12-05-2002, 06:32 PM
With Merit and 2,4-D being broad-based insecticides and herbicides does anyone know of studies that show the effects on earthworm populations in treated soils? I would have to assume that earthworm populations would decrease in soils that are treated with these chemicals and a result would be increasing your dependence on aerators, dethatchers and fertilizers.

Lawn Sharks
12-05-2002, 06:53 PM
I found some other statistics regarding Merit (Imidacloprid)

While it may take 3/4 lb to kill you it seems to have a few nasty side effects. Can't say I would want my kid playing on a lawn treated with this stuff.


* Imidacloprid is a relatively new, systemic insecticide chemically related to the tobacco toxin nicotine. Like nicotine, it acts on the nervous system. Worldwide, it is considered to be one of the insecticides used in the largest volume.

* It has a wide diversity of uses: in agriculture, on turf, on pets and for household pests.

* Symptoms of exposure to imidacloprid include apathy, labored breathing, incoordination, emaciation and convulsions. Longer-term exposures cause reduced ability to gain weight and thyroid lesions.

* In studies of how imidacloprid affects reproduction, exposure of pregnant laboratory animals resulted in more frequent miscarriages and smaller offspring.

* An agricultural imidacloprid product increased the incidence of a kind of genetic damage called DNA adducts.

* Imidacloprid is acutely toxic to some bird species, including sparrows, quail, canaries and pigeons. Partridges have been poisoned and killed by agricultural use of imidacloprid. It has also caused eggshell thinning.

* The growth and size of shrimp are affected by imidacloprid concentrations of less than one part per billion (ppb). Shrimp and crustaceans are killed by concentration of less than 60 ppb.

* Imidacloprid is persistent. In a field test in Minnesota, the concentration of imidacloprid did not decrease for a year following treatment. It is also mobile in soil, so is considered by the U.S. Environmental Protection Agency to be a potential water contaminant.

* The development of resistance to imidacloprid by pest insects is a significant concern. In Michigan potato fields, the Colorado potato beetle developed resistance to imidacloprid after just two years of use.

Lawn Sharks
12-05-2002, 07:00 PM
Found the earthworm info I was looking for on Merit at least. Still have found it for 2, 4-D

Here is what I found for Merit:

"Imidacloprid effects on earthworms

Earthworms are an important part of the soil ecosystem. In a typical soil, about 80 percent of the animals, by weight, are earthworms. They make important contributions to soil fertility and the breakdown of organic material. (51) Imidacloprid is acutely toxic to earthworms; for example, the LC (50) of the species Eisenia fetida is between 2 and 4 ppm in soil.51

At lower concentrations, other effects occur. The activity of the enzyme cellulase, which is found in the earthworm's gut and allows it to break down plant litter, is reduced by imidacloprid concentrations of 0.2 ppm.(52) The frequency of deformed sperm in earthworms was increased by a soil concentration of 0.2 ppm. The frequency of damaged DNA (genetic material) in earthworms was increased by a concentration of 0.05 ppm.(51)"


50. U.S. EPA. Office of Prevention and Toxic Substances. 1993. Screen of the NTN 33893 microcosm study. Memo from A.F. Maciorowski, Ecological Effects Branch, to D. Edwards, Registration Div. Washington, D.C., Apr. 19. p. 10.

51. Zang, Y. et al. 2000. Genotoxicity of two novel pesticides for the earthworm, Eisenia fetida. Environ. Pollut. 108:271-278.

52. Luo, Y. 1999. Toxicological study of two novel pesticides on earthworm, Eisenia foetida. Chemosphere 39:2347-2356.