Turf & Rec

Features Agronomy
A look at corn gluten meal as a herbicide


June 17, 2009
By William Gathercole

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Corn gluten meal is a “natural” turf herbicide and is derived from plant materials. It is a byproduct of the corn wet-milling process and is used for animal feed. It also contains 10 per cent nitrogen by weight, and is a source of nitrogen.

Corn gluten meal is also classified as a pre–emergent herbicide, which means that it “inhibits” annual-type weeds before they germinate and sprout from the soil. It has no post-emergent effect on weeds, and, unfortunately, it may actually increase the growth of established weeds since it does provide nitrogen with every treatment. This product will not provide the eradicative effect as post-emergent 2,4-D herbicides like Killex, and is certainly not an effective alternative.corngluten

Corn gluten meal must be applied before weed seeds germinate, which means during the months of spring in most cases. It will only work for a limited time period of approximately 35 to 45 days. In fact, corn gluten meal has been patented as a natural pre-emergent herbicide for the control of annual weeds in turfgrass, such as crabgrass. Following treatment, weed seedling shoots will emerge normally, but the development of the emerging root is inhibited by corn gluten meal. After a period of water stress, the seedlings wilt and die because their root systems do not develop properly. By contrast, 2,4-D herbicides like Killex will quickly destroy the entire plant, and can be applied at almost any time of the season. A program of one to three applications of Killex will provide season-long control of the majority of broad-leaved weeds. Corn gluten meal will fail to control weeds at the same level as a Killex program.

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Corn gluten meal will not control the majority of weeds in turf.
Crabgrass is the most common target of corn gluten meal products. The
developing roots of the following weeds are known to be adversely
affected by corn gluten meal:

• Barnyardgrass
• Clover
• Crabgrass
• Creeping bentgrass (in home lawns)
• Dandelion
• Foxtail

Corn gluten meal is not a true alternative to using 2,4-D herbicides,
which themselves act as a post-emergent herbicide, destroying  most
broad-leaved weeds that have already emerged from the soil.

Despite the fact that this product is “natural,” corn gluten meal may
cause sensitization to the skin and eyes. For the sake of comparison,
“Killex Turf Herbicide,” which contains 2,4-D, may cause severe
irritation to the eyes. This is another example of a “natural” product
that is alleged to be “low-risk” or “safer” when compared to
conventional products, but, in fact, is not really so.

From a safety standpoint, corn gluten meal is not significantly
different from conventional 2,4-D herbicides like Killex, nor is it a
true weed control alternative.