Pesticides and Earthworms......

Discussion in 'Pesticide & Herbicide Application' started by Lawn Sharks, Dec 1, 2002.

  1. Lawn Sharks

    Lawn Sharks LawnSite Senior Member
    Posts: 394

    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 :

    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
    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."
  2. KLR

    KLR LawnSite Member
    from Zone 6
    Posts: 171

    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'
  3. Lawn Sharks

    Lawn Sharks LawnSite Senior Member
    Posts: 394

    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.

  4. KLR

    KLR LawnSite Member
    from Zone 6
    Posts: 171

    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
  5. Lawn Sharks

    Lawn Sharks LawnSite Senior Member
    Posts: 394

    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.

  6. KLR

    KLR LawnSite Member
    from Zone 6
    Posts: 171

    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 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
  7. Lawn Sharks

    Lawn Sharks LawnSite Senior Member
    Posts: 394

    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."


    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."


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

  8. tremor

    tremor LawnSite Bronze Member
    Posts: 1,476

    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.

  9. KLR

    KLR LawnSite Member
    from Zone 6
    Posts: 171

    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.
  10. tremor

    tremor LawnSite Bronze Member
    Posts: 1,476

    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.



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