| A Shotgun Approach to Plant Health © Copyright 2007 K. E Woodard A Shotgun Approach to Plant Health is a companion booklet to My Shotgun Approach To Wellness. The "Wellness" publication illustrates how a variety of fruits, nuts, vegetables, herbs, vitamins, minerals and other factors, including exercise and prayer, are used in an attempt to stave off disease and old age. Plant health is akin to human health in that given the essential nutrition and a proper environment both are quite able to successfully defend against parasitic invaders. The present work will explore the advantages and disadvantages of a shotgun approach to plant wellness. Corn Meal: The Misunderstood Plant-Disease Fighter In the early 1990s, a commercial peanut grower in Comanche County, Texas was informed that corn meal lightly incorporated into the soil might control a fungal disease that was devastating his crop. "Bull corn! And you can kiss my grits!" the farmer replied. That was the typical reaction to studies coming out at the time involving use of corn meal as a fungicide. Although there were very promising results from small plots using corn meal to combat a particular destructive peanut disease, the idea wasn't to the typical grower's liking. And then there is the home gardener. He or she doesn't have to worry about making a living growing stuff. A gardener has to impress only a few neighbors and the county agent with his green thumb. The home gardener is a pioneer - a gambler - itching to try the newest fad, the latest wrinkle to grow a larger melon, a tastier tomato, and more of anything. Afraid! He would likely trade his front seat in hell to be the first to successfully incorporate a new skill or product. The Reason Why (Short Version) The short version is for those who want the bare essentials of how to make corn meal work so they can get on with their lives. The longer version is for those who crave the entire story so they can find the flaws and make it better. Misinformation #1 - Corn meal works because it stimulates soil antagonists, primarily Trichoderma spp. (a fungus), to control fungal plant pathogens. Stimulate is not the best choice of words here. Trichoderma spp. utilizes corn meal very efficiently as a growth substrate, or food. But so do several plant pathogens including Rhizoctonia solani, the fungus that causes the familiar brown patch of turfgrass. Is there an advantage to adding corn meal as a "stimulant" to an established disease infested area if corn meal also "stimulates" the pathogen? Misinformation #2 - Trichoderma spp. is in every soil and ready to be "stimulated" to control a pathogen. (Note: spp. indicates that there is more than a single species.) Reality Check #1 - Corn meal is contaminated with a host of bacteria and fungi. The dominant fungal contaminant is generally Trichoderma spp., a proven antagonist to many plant pathogens. When corn meal is added to a diseased area, Trichoderma spp. is also added to the area attached to its food source. The added Trichoderma spp. plus the indigenous Trichoderma spp. can combine forces to overwhelm a pathogen. Reality Check #2 - Corn meal can be contaminated with plant pathogens and low populations of Trichoderma spp. The population of corn meal contaminants depends, for the most part, on the environment where the corn is grown and processed. This is the plausible explanation of why corn meal works sometimes and doesn't work at other times. In short, corn meal products are not all the same. Some have more Trichoderma spp. than others. Some contain pathogens that may be released with a corn meal application. Reality Check #3 - Grain sorghum meal has been proven to be as effective as corn meal in introducing Trichoderma spp. to a diseased area. Undoubtedly, meals from other grain sources will work the same as corn meal and grain sorghum meal. Solution - Mix and apply corn meal (or other ground up products) to diseased areas. For example: Purchase a pound bag each of Aunt Jemima yellow corn meal, Aunt Jemima white corn meal, and HEB's brand of yellow corn meal. Thoroughly mix the contents in a suitable container. Make applications to diseased areas from contents of the mixing container. The idea here is to get a variety of disease antagonists because the source of each corn meal represents a different environment. This is the shotgun approach personified! Compatibility - If a synthetic fungicide is being used in addition to corn meal, it must be compatible with Trichoderma spp. For example: If chlorothalonil is being used to treat a foliar disease and corn meal is being used to treat a soil-borne disease on the same plant, chlorothalonil will impede Trichoderma spp. while a copper based foliar fungicide tends to enhance the Trichoderma spp. What is the best way to apply corn as a fungicide? It has been established that corn seeds carry a colonized microflora (bacteria & fungi) and that some of it has a potential to control plant pathogens. It stands to reason that the more surface area a corn seed has, the more microflora it will harbor. With this reasoning, corn flour would have the most surface area, followed by corn meal, grits, coarsely ground field corn and cracked field corn. The latter two have the smallest surface area for colonization, however, they retain a high oil content germ (embryo) which offers additional nutrients for colonization and survival. Field corn will normally be the least expensive. Corn meal, as is, will never make it as a fungicide for large commercial field crops except perhaps for spot treatment of small infested areas. On the other hand, corn meal is a natural for home gardeners. It is relatively inexpensive, easy to apply, effective, and most importantly, safe. In addition, it is a good fertilizer. The only down side is the possibility of stimulating the target pathogen being treated and the slight chance of introducing a new pathogen with the corn meal. Rate to Use Research with corn meal on Sclerotinia blight of peanut indicated a rate of 400 pounds per acre to be effective. Twenty pounds per 1000 sq. ft. of lawn grass infested with the brown patch fungus has been recommended on some radio garden shows. How do the above rates translate to a single rose bush? About a handful of corn meal for a plant 2-3 feet tall. Or a handful of corn meal per 3-5 row-ft. of smaller garden plants such as beans or peas. More is not necessarily better. A point can be reached where the beneficials seem to be competing among themselves more than with the pathogens. The corn meal application should be incorporated lightly into the soil to protect it from direct sunlight. Keep in mind also that corn meal is an excellent growth medium for some pathogens such as Rhizoctonia solani (brown patch of turf grasses) and Sclerotium rolfsii (Southern blight). Conversely, corn meal as a growth medium retards mycelial growth of Sclerotinia minor. These facts illustrate again the need to correctly identify the pathogen before treatment. See Books for details of purchase of booklet or e-mail ken@kenwoodardbooks.com |
