The label is the law. Read your product's label before you mix or apply; the rates here come from the labels listed under Sources.
- Active ingredient
- Corn gluten meal (CAS 66071-96-3)
- Chemical class
- A byproduct of corn wet milling that is about 60 percent protein and is used in livestock, poultry and pet feeds. It is one of the active ingredients allowed in minimum-risk pesticides.[5][1]
- Mode of action
- Bioactive peptides from the meal stop germinating seeds from forming roots; leaves emerge but the seedlings have no roots to support them[6][5]
- Registration
- None: exempt from federal registration as a minimum-risk pesticide (40 CFR 152.25(f)); no EPA signal word.[1]
Why it has no EPA registration number
Corn gluten meal is listed in Table 1 of 40 CFR 152.25(f), the active ingredients allowed in minimum-risk pesticides. A product made only from listed active ingredients and permitted inert ingredients is exempt from federal registration if it meets every condition, which include naming each active ingredient with its percentage by weight on the label and giving the company's name, street address and phone number.[1]
EPA does not review these exempt products, so a label shouldn't claim EPA endorsement or show an EPA registration number, which could lead buyers to think EPA had reviewed it. States may still require the products to be registered under state law.[2][3]
Illinois Extension warns that some lower-cost products sold as corn gluten don't contain enough protein to work as an herbicide. If you want weed prevention rather than only fertilizer, choose a product labeled as a weed preventer.[6]
What to expect
Results may not be obvious after one application in the first season, and Iowa State says control improves with every year it is used. Heavy rain or irrigation after spreading reduces its effect, and Illinois Extension expects better results where springs are dry.[5][6]
Most spreaders can't put down 20 lb per 1,000 sq ft in a single pass, so plan on several passes. Because it also stops desirable grass seedlings from rooting, don't seed or overseed where you apply it.[6]
The nitrogen releases slowly as the meal breaks down, so it also feeds the lawn, and Iowa State notes that a thicker lawn leaves fewer places for weeds to get started.[6][5]
In gardens it can be used around established perennial flowers, and in a vegetable garden once transplants and seedlings are established. UC IPM also lists corn gluten meal as a rodenticide ingredient.[5][4]
Where it is used
It only works on seeds as they germinate. It has no effect on weeds that are already established and will not kill any established plant.[5][6]
Iowa State lists crabgrass, barnyardgrass, foxtails, dandelion, lambsquarters, pigweed, purslane and smartweed among the weeds it is labeled to control at germination.[5]
The weed-preventing rate is 20 lb per 1,000 sq ft, spread evenly and watered in lightly. The soil then needs to dry out somewhat for a few weeks so the sprouted seedlings dry up and die.[5][6]
In Iowa, the timing is mid-March to early April, at least three to five weeks before crabgrass seeds germinate, with a second application in mid-August for late-season annual weeds. Illinois Extension times it to forsythia bloom, or to shallow soil that stays at 55 °F or warmer for 5 to 10 days in a row.[5][6]
Safety and environmental hazards
People
Corn gluten meal is the same material sold as a protein supplement in feeds for livestock, poultry and pets. EPA does not review minimum-risk products, and UC IPM's database has not yet published acute or chronic toxicity ratings for corn gluten meal. NPIC's advice is that no matter how natural, all pesticides should be used with care and exposure kept low.[5][2][4][3]
Pets
Corn gluten meal is an ingredient in livestock and pet foods. Because EPA does not review minimum-risk products, there is no EPA-reviewed pet hazard statement for them; NPIC advises following the label and minimizing exposure to animals.[6][2][3]
Bees and pollinators
UC IPM's database lists the honey bee rating for corn gluten meal as information still to be added. Products are powders or granules spread over the lawn or garden soil.[4][5]
Fish and water
UC IPM has not yet published a water-quality rating for corn gluten meal. It is about 10 percent nitrogen by weight, so the 20 lb per 1,000 sq ft weed-control rate supplies roughly twice the 1 lb of nitrogen per 1,000 sq ft that Illinois Extension recommends in one application, and in some sensitive watersheds applying nitrogen at that rate may be illegal.[4][6]
Common questions
- Does corn gluten meal kill weeds that are already growing?
- No. It only affects seeds as they germinate and has no effect on established weeds, so apply it before weed seeds sprout.[5][6]
- Can I overseed my lawn after using corn gluten meal?
- Not at the same time. It keeps desirable lawn seedlings from rooting too, so Illinois Extension advises against seeding or overseeding when you apply it.[6]
- Why doesn't my corn gluten weed preventer have an EPA registration number?
- Corn gluten meal is a listed minimum-risk active ingredient, and products that meet all the conditions in 40 CFR 152.25(f) are exempt from EPA registration. EPA doesn't review them, and some states require them to be registered under state law.[1][2]
- Is corn gluten meal also a fertilizer?
- Yes. It is about 10 percent nitrogen by weight and releases it slowly as it breaks down. At the 20 lb per 1,000 sq ft rate used for weed control, that is more nitrogen than Illinois Extension recommends in a single application.[6]
Sources
- Electronic Code of Federal Regulations, “40 CFR 152.25(f), Minimum risk pesticides.” www.ecfr.gov/current/title-40/chapter-I/subchapter-E/part-152/subpart-B/section-152.25 (accessed 2026-11-08)
- U.S. EPA, “Conditions for Minimum Risk Pesticides.” www.epa.gov/minimum-risk-pesticides/conditions-minimum-risk-pesticides (accessed 2026-11-08)
- National Pesticide Information Center, “Minimum Risk Pesticides.” npic.orst.edu/ingred/ptype/minrisk.html (accessed 2026-11-08)
- University of California Statewide IPM Program, “Home and Landscape Pesticide Active Ingredients Database: corn gluten meal.” ipm.ucanr.edu/home-and-landscape/pesticide-active-ingredients-database/active-ingredient-details/?uaiKey=127 (accessed 2026-11-08)
- Iowa State University Extension and Outreach, “How to Use Corn Gluten Meal as Herbicide in the Lawn and Garden (last reviewed June 2025).” yardandgarden.extension.iastate.edu/how-to/how-use-corn-gluten-meal-herbicide-lawn-and-garden (accessed 2026-11-08)
- University of Illinois Extension, “Corn Gluten Meal: Can it naturally prevent weeds and feed your lawn? (Good Growing, March 27, 2026).” extension.illinois.edu/blogs/good-growing/2026-03-27-corn-gluten-meal-can-it-naturally-prevent-weeds-and-feed-your-lawn (accessed 2026-11-08)