June 5, 2002
Corn gluten:
Placebo or panacea as a lawn care alternative?

By Rita Weerdenburg

In the ongoing battle between environmentalists seeking to eliminate all pesticide use for what is commonly referred to as “cosmetic use,” and the lawn care industry striving to serve their ever increasing numbers of clients who are demanding lush, green and weed-free lawns, is it possible that science has possibly stumbled onto an alternative that will satisfy both?

     Growing attention is now being focused on a product known generically as corn gluten meal. A by-product of the wet milling process for the production of corn syrup, corn gluten is high in protein and is generally used as animal feed. Its potential as a weed control agent was discovered by accident when researchers at Iowa State University used corn meal as an agent to establish Pythium fungi in the soil as a potential method of controlling the germination of creeping bentgrass. In short, the original objective of the experiment was a failure, but observant scientists did notice a reduced rate of weed seed germination in those plots that had received the corn meal over those that had not. Under the direction of the university’s Dr. Nick Christians, greenhouse studies were conducted to determine if this was more than a coincidence and if not, which specific components of the corn meal would affect the greatest amount of weed control.

     After conducting studies using corn meal, corn starch, corn gluten meal and corn seed fibre, it was eventually determined that the corn gluten meal held the highest potential as a pre-emergent herbicide. Further studies were then conducted to determine effective rates of application and other criteria that would determine the overall potential of this natural product for consumer use. These studies showed that the corn gluten meal actually affected the root development of the germinating seed, but shoot development was normal. Inadequate root development, together with a drying soil surface, caused the decline of the emerging weeds. Plants with well-established roots were not adversely affected.

     In fact, because corn gluten meal is approximately 60 per cent protein and 10 per cent nitrogen by weight, it is actually a natural source of slow release nitrogen, and as such, beneficial to turf.

     So is corn gluten meal nature’s perfect “weed and feed” product? While its herbicidal and nutritive qualities have been proven under controlled testing environments, it is less clear how well this product will perform in the real world. Correct timing and relatively high rates of application are integral to the success of corn gluten meal as a pre-emergent herbicide. If not applied on time, corn gluten meal will actually help to promote the growth of weeds, along with the rest of the turf.

     The recommended rate and timing of application is 20 lbs./1,000 sq. ft. before germination of annual weeds in the spring, followed by a second, similar application in late summer. And, although a thorough watering at the time of application is recommended, a subsequent dry period is also necessary for corn gluten meal to be effective. In wet springs, one runs the risk of applying an expensive product that will help, rather than hinder, weed growth. The rate of application, along with its current market price makes corn gluten meal a risky venture for some.

     Even with these risks aside, getting corn gluten meal to market is proving to be a tricky business, especially here in Canada. For any product — even those that are 100 per cent natural — to be labelled and marketed as a pesticide, it must first be tested and approved by the federal government’s Pest Management Regulatory Agency (PMRA).

     Explains Ontario Ministry of Agriculture, Food and Rural Affair’s (OMAFRA) Pam Charbonneau, “Because corn gluten meal is a simple by-product of a common manufacturing process, it is a public domain product, available to anyone. And without exclusive rights, it is doubtful that any company will be willing to absorb the costs involved in obtaining PMRA approval. So anyone can buy and apply corn gluten meal, but legally, they can’t tell their customers they are applying a pesticide or even a completely natural pesticide.”

     Its nitrogen content adds significant value to corn gluten meal as an herbicide, but it cannot stand alone as a good natural fertilizer alternative. Without a legal means of telling customers about the benefits of this product, the future of corn gluten meal is dubious at best.

     South of the border, on the strength of the patented, licensed name of A-Maizing Lawn, corn gluten meal has been registered with the Environmental Protection Agency (EPA). Some attempts are also being made to market similar branded products here in Canada, but the claims as to their herbicidal properties are, of necessity, ambiguous at best.

     Here in Canada, there is a reasonable expec­tation that corn gluten meal may be a good candidate for a PMRA exemption, although bureaucratic hold-ups are likely. Should that be the case, we can expect several companies will endeavour to develop market brands for nature’s weed and feed. After that, only time will tell whether there is a long-term future for corn meal gluten in the real world where the need for environmentally friendly alternatives continues to clash with the need for instant, cost-effective and weed-free turf.