Cornmeal has been shown to be an effective fungicide. But before using it, first you need to make sure that fungus is a problem in your garden.
Just as some insects are beneficial to gardens while some are pests, fungus can be either beneficial or harmful. It is important not just to determine if there is fungus in your garden, but also if it is a kind that you don’t want.
If you see a whitish, mildew-like powder spread over the leaves of the plants in your garden like a light dusting of snow, this is a bad sign. This fungus will develop as small circular patterns or spotty white dots on the leaves, and gradually eat away at them.
Another sign to look for if you have rye grass is something that looks like little cotton balls in the grass. This fungus starts on the rye grass but soon spreads and attacks other plants as well.
Another indication of harmful fungus is if you have apple trees, and the branches turn a bright red or yellow, usually in the spring or early summer. The limbs will eventually drop off, and then the trees themselves will die if left untreated.
Harmful fungus can also start in mulch and then spread to nearby plants. A sign of this fungus can be found at the base of your house or garage near where you have mulch. It appears as small brown splotches that work their way up the wall.
If you encounter any of these fungi in your garden, a fungicide is in order, or you will be dealing with potentially major damage to your plants.
If you prefer using only organic pesticides and fungicides, an option worth considering is cornmeal. (Not corn gluten though. That’s a special processed version of cornmeal that will have different effects-both good and bad-in your garden from those of regular cornmeal.)
Researchers at Texas A&M University investigated the fungicidal potential of cornmeal after noticing that a peanut crop planted following a corn crop was surprisingly free of the usual fungus diseases. What they found was that cornmeal promotes the growth of beneficial fungus that tends to attack the harmful types of fungus. Sorghum meal and meal from other grain sources appears to have some effectiveness as fungicides as well.
Cornmeal can be used either dry or as a spray. To use it dry, work 2 pounds of cornmeal into every 100 square feet of soil, once per season. Water the area to foster the growth of the good fungus from the cornmeal.
To use as a spray, soak one cup of cornmeal in one gallon of water overnight, and then strain. Spray where you see the bad fungus, or as a preventative on plants you believe could be vulnerable to the bad fungus.
Finally, to save money, you need not buy food grade cornmeal. Horticultural cornmeal is cheaper because it does not come under the same strict guidelines as cornmeal that will be used to feed people, but it has the same fungicidal effects.
Marie Iannotti, “Cornmeal Has Powerful Fungicidal Properties in the Garden.” About.com.
K.E. Woodard, “A Shotgun Approach to Plant Health.” Ken Woodard books.
“How to Identify Detrimental Fungus in Your Garden.” Doityourself.com.