How To Treat Lawn Disease Organically

Is Using Cornmeal to Treat Lawn Disease a Myth?

Not only does Dr. Linda Chalker-Scott consider the use of cornmeal as a fungicide a myth, an article from 2010 claims the myth is busted. Dr. Linda Chalker-Scott is the author of The Informed Gardener and numerous articles on horticultural myths

When I discovered Dr. Chalker-Scott's myth articles online a few years ago I read threw them all and found myself mostly agreeing with a lot of the content and was able to find corroborating work in other studies from what I remember. I even referenced her when I was asking myself... does SuperThrive work?

In this case however I find I can't agree with everything she says. Sadly, from the time I first started writing this piece, some of the links I originally quoted are now broken but I've tried to find similar research. The original article wasn't meant to be a rebuttal to Dr. Chalker-Scott but I tried to incorporate her opinions in the new version.

Note I actually started writing this article one or two springs ago which is why I have reference to all the rain. Right now it's the middle of summer and there hasn't been much if any rain but I'm leaving that verbage intact to illustrate what I was seeing at the time. I decided to finish it after seeing Dr. Chalker-Scott's article recently.

Well, it's been raining here for quite some time and it's going to continue for another week it seems. I've touched on the issue of lawn disease recently and it should come as no surprise considering the wet weather.

In the few breaks in the rain, I've managed to get in a few bike rides and there are plenty of brown, yellow or orange tinged lawns throughout the neighborhood. Brown and yellow could just be a result of lawn crews waiting too long to cut the grass as they try and squeeze what they can in between downpours but most likely a good bit of it is due to fungus caused by all the moisture and landscapers that are mowing the grass when it's wet because they can't afford to wait for dry weather.

As I look over my lawn and compare it to the neighbors there is a vast difference in color. Mine is a nice dark green, theres is a mixture of light green and orange (grorange?) Part of the reason for that is a much discussed organic fertilizer that tends to make people laugh or look at me funny when they hear what it is.

In the early morning when other's are mixing up cornmeal for muffins, I'm out spreading it on my lawn. Plain old corn meal that you can get from the supermarket. (Not corn gluten meal.) I've posted about corn meal recently (where to buy big bags of corn meal, how to get organic corn meal delivered every month or two) but with so many grorange lawns out there I thought it might be good to explain it a little more about how it works and how to use it as well as some other organic fungicides.

How Corn Meal Cures and Prevents Lawn Disease

Well the truth is, corn meal doesn't kill fungus. In fact, it does the opposite. I can hear you now saying "But you said...." Hear me out.

With organic lawn care, you're not usually solving the problem in one step. Instead you create a condition where beneficial organisms can thrive and/or add beneficial organisms. Such is the case with cornmeal.

The beneficial organism in this case is trichoderma, a family of cannibalistic fungi that kill other fungi. When you apply cornmeal to your lawn you're not killing lawn disease, you're supplying the troops of trichoderma so they can multiply and wage war on lawn disease.

The video isn't in a language I speak but I'm pretty sure based on the title and the footage that this is a video of trichoderma killing sclerotinia. A form of sclerotinia occurs in lawn and is commonly referred to as Dollar Spot.



Trichoderma are found in most soils and grow well on corn meal. Corn meal, like everything else that hasn't been sterilized, also harbors bacteria and fungi and trichoderma is a common fungi to find on cornmeal (I think from what I read). Even if it's not on the cornmeal it's a fungus that's commonly found in soil.

Three of the species of trichoderma that are used to fight plant and lawn disease are trichoderma harzianum, tricoderma viride and trichoderma hamatum. They are parasitic and feed off other fungi in a variety of ways. Trichoderma harzianum for instance can excrete and enzyme called chitinase under the right conditions. Chitinase breaks down, hydrolizes, digests, whatever you want to call it, chitin which is what the cell walls of fungi are made of. It basically disolves other fungi.

There are (were?) ongoing university studies that have shown promise using corn meal to treat plant diseases such as this study on controlling fungi in peanut fields with corn meal (link no longer works but is available on archive.org referenced here). My emphasis added.

It is known that certain fungal species in the genus Trichoderma feed on mycelium and sclerotia of Sclerotinia minor. Sclerotium rolfsii and Rhizoctonia sp. All peanut fields in Texas tested to date have a natural population of Trichoderma. For several years, tests have been conducted in Texas using corn meal to stimulate Trichoderma development as a way to control the major soilborne disease fungi. When yellow corn meal is applied to fields in the presence of moist surface soil, Trichoderma builds up very rapidly over a 5 to 10 day period. The resulting high Trichoderma population can destroy vast amounts of Sclerotinia, Sclerotium and Rhizoctonia. This enhanced, natural biological control process is almost identical to the processes that occur when crop rotation is practiced. The level of control with corn meal is influenced by: 1) organic matter source 2) soil moisture, 3) temperature, and 4) pesticides used. Seasonal applications of certain fungicides may inhibit Trichoderma. Testing will continue to determine the rates and application methods that will give consistent, economical control.

The above quote is the reason why some of us started using cornmeal on our lawns in the first place. Dr. Chalker-Scott calls it "research" (with quotes) indicating it wasn't really following the scientific method. It's hard to say without being able to see the original report but from what I remember it seemed to have been conducted using sound principles. From what I recall, they didn't just guess that trichoderma populations increased, they actually examined the soil.

Dr. Chalker-Scott also claims the study just proved that crop rotation is a beneficial practice that can prevent disease. That's not what I'm reading here.

I'm not much of a conspiracy theorist but I do find it odd that the original paper and some of the others I linked to below are no longer online.

The study that led to the discovery of corn gluten meal as a weed control also had an interesting observation regarding corn meal and lawn disease. The original study was regarding pythium on bentgrass. Pythium was cultured in the lab on corn meal, which is a common growth media for such fungus. There were three plots observed. A plot which received the pythium and corn meal, a plot which received fresh corn meal without pythium grown on it and a third control plot which did not receive any pythium or corn meal. Pythium failed to establish in the treated plot where the pythium grown on corn meal was applied. It seems Dr. Nick Christians Ph.D. focused more on the lack of germination in the corn meal plot as I can't find any documentation that he tried to determine why the pythium may not have established.

The previous quote from Texas A&M doesn't say anything about lawns or common lawn diseases does it? Hmm... OK this is the problem with organic research. While it has been studied for a long time, it unfortunately hasn't been that long and you may not find direct evidence of exactly what you're looking for. So this is what we do, or I do at least. I'm not the type of person that likes to waste money and see if something works just because someone said it does. I want to see something that justifies the claim. Sometimes you can't get to it directly so you have to find corresponding research and peice it together without getting so convoluted that it looks like a Chewbacca defense.

Now that we know it's not actually cornmeal that's curing the lawn disease all we have to do is look for research that indicates trichoderma is effective at killing a particular diesease. That shouldn't be too hard because according to the Wikipedia article there's a strain of trichoderma that can kill almost any other fungus and trichoderma is found in all soil. Maybe not in soil that has been treated with some fungicides such as chlorothalonil (Daconil) but some species of trichoderma seem to be resistant to copper based fungicides.

Lawn Diseases That Corn Meal Can Treat

Well theoretically treat that is. I'll be updating this list as I have time but here's a quote from a Cornell publication on trichoderma:

So far as the author is aware, different strains of Trichoderma control every pathogenic fungus for which control has been sought. However, most Trichoderma strains are more efficient for control of some pathogens than others, and may be largely ineffective against some fungi. The recent discovery in several labs that some strains induce plants to "turn on" their native defense mechanisms offers the likelihood that these strains also will control pathogens other than fungi.

These are common lawn diseases that trichoderma attacks. If you can get trichoderma to grow on your applied cornmeal then there's a chance for corn meal to treat the following:

Sclertinia (Dollar Spot) - See video above and this paper found trichoderma provided up to 71% control of dollar spot and was able to delay disease development by up to 30 days.
Botrytis (Grey mold) - An interesting study at Cornell (link dead) using bees to disseminate Trichoderma harzianum to protect strawberries from Botrytis was effective. Here's a working link that discusses using trichoderma to suppress Botrytis of Begonia in a peat/compost potting mix.
Pythium - A nasty lawn disease can be controlled with trichoderma harzianum and trichoderma virens according to this PSU paper. There are even two products that contain trichoderma that are EPA registered for treating pythium. The link to the paper is gone but this PSU fact sheet indicates Trichoderma harziamum, Trichoderma virens as well as Bacillus subtilis, Candida oleophila, Gliocladium catenulatum and Streptomyces griseoviridis are biological controls of pythium.
Fusarium (Summer Patch) - There are a number of documents indicating trichoderma is effective against fusarium including this Colorado State study on trichoderma against fusarium on tomatoes.
Necrotic Ring Spot - This publication indicates trichoderma hazrianum is effective against necrotic ring spot in laws and that there is an EPA registered product.
Drechslera tritici-repentis (Leaf Spot) - In vitro study showed Trichoderma "inhibited significantly the mycelial growth ofD. tritici-repentis between 50% and 74%"
Rhizoctonia solani (Yellow Patch) - This in-vitro study showed that various strains of trichoderma were up to 81.8% effective at inhibiting mycelial growth of Rhizoctonia solani.

Organic Products With Trichoderma

In researching the topic I found a number of different products that contained trichoderma that were EPA registered fungicides.  The first time I used cornmeal on my lawn I did it without adding anything else and I found the application of cornmeal was beneficial to my lawn. It may have been the tricoderma, it may have just been that my grass needed fertilizer and the extra boost it got from the cornmeal allowed the grass to grow out of the disease or make it healthier so it could resist it. I'm not a horticultural specialist and I don't have the tools to know the difference.

These days, when I apply cornmeal to my lawn I also apply Organica Plant Growth Activator Plus using a pump sprayer that I filled up 2 days prior to allow the chlorine to outgas. Chlorinated water can kill the beneficial fungi I'm trying to spread. Humic acid and ascorbic acid (Vitamin C) are also said to reduce chlorine in water.

Organica's Plant Growth Activator Plus contains a number of beneficial bacteria and fungus some of which have been shown to prevent or control plant and lawn disease. It contains:

• Trichoderma hazianum 2,000,000 CFU per gram. 
• Bacillus subtilis 10,000,000 CFU per gram. 
• Bacillus licheniformis 10,000,000 CFU per gram, 
• Bacillus megaterium 10,000,000 CFU per gram, 
• Paenibacillus polymyxa 10,000,000 CFU per gram, 
• Streptomyces lydicus 2,000,000 CFU per gram, 
• 30% natural sugars, 
• 10% hydrolyzed soy meal 
• 4% humic acid (derived from leonardite), 
• 3% seaweed extract (derived from Ecklonia maxima). 

I can't find a link to the original Rutgers study but it's referenced here. Application of PGA+ every 2 weeks was able to control around 90% Summer Patch (Magnaporthe pose) on Baron Kentucky Bluegrass which is similar to the control rates of the other commercial chemical based fungicides. Even after application stopped the PGA+ test plot continued to provide effective control.

Organica's PGA+ is a product I looked into quite a bit and is something I apply in my garden regularly. The kelp and humic acid seem to work well together to reduce plan stress from what I've read.

Compost Helps with Plant Disease

A number of different studies and test plots using compost have shown it does wonders for treating all sorts of plant problems. The organic matter improves soil texture, the added microbiology improves plant fertility and health and I even read one EPA brochure that described a Superfund site that had explosives in the soil that was remediated with compost.

Compost can even be tailored in a way that is more bacterial or more fungal to deal with different conditions. Good compost can make big improvements to your soil. Good soil means good plants.

So Does Cornmeal Cure Lawn Disease?

One comment Dr. Linda Chalker-Scott made which I do agree with is that there hasn't been enough scientific research to definitively prove if it does or not. She also stated that she can't prove a negative (that it doesn't work) and that it's up to those that are making the claims that it does work to prove it does.

I thought that's what the original Texas A&M group was doing and can't figure out why that link no longer works.

Here's what I do know:

• Various strains of trichoderma (as well as other fungi) are grown on corn or corn agar when researches need to cultivate a given quantity of the fungi. It is a good growth medium for such.
• Various strains of trichoderma have been shown in different studies to have effective control of various plant pathogens including ones that are found in lawns.
• Trichoderma are found in nearly all soils.

Here's what I assume:

• Since corn meal is a good base to grow fungi adding cornmeal to moist soil should be able to increase the population of those fungi.
• Since trichoderma is some sort of predator fungi that kills other fungi it's understandable that the population of trichoderma would outcompete the other fungi growing on the cornmeal medium since it will attack those other fungi. 

I think there's enough evidence related to using cornmeal and trichoderma to control lawn and plant disease that further research is warranted.

So what's the problem? Where's the research?

OK, it's time to put my tin-foil hat back on. Research isn't cheap. It takes time, resources and money. University research labs need to have funding to carry out their experiments. Who pays for that research? Some of it comes from government grants but I believe most of it comes from companies that are developing and patenting products for eventual sale. They work with university researches to determine if their new product works or not and try to improve it. They are willing to pay to have that research done.

Who is going to pay to research cornmeal? It's not patentable. It can't be sold as a commercial product.

You also need to be EPA registered if you claim your product is a fungicide. That's not free either.

More research needs to be done as fungicides are some of the more toxic things applied on lawns, but just because she can't verify the claims doesn't mean Dr. Chalker-Scott can call this myth busted.

So Does Cornmeal Cure Lawn Disease?

No, cornmeal doesn't cure lawn disease but there is some evidence that suggests cornmeal can feed beneficial organisms in the soil which in turn can control lawn and other plant pathogens. A lot needs to happen for that to happen. The beneficial must already exist in the soil or be inoculated in the soil or cornmeal and the soil needs to be free of anything that could inhibit the growth of these beneficial microorganisms such as fungicides, pesticides and chlorinated water.

This follows the practice prescribed in other organic lawn care practices. Develop a healthy soil with a thriving population of beneficial organisms and your plants will grow well. Different soil biology responds to different soil amendments. Some trigger increased bacterial activity while others trigger increased fungal activity. Cornmeal appears to help with beneficial fungal activity.