Corn Gluten Meal for Crabgrass
Control
The idea of using corn gluten meal for weed control burst on the scene
in the early 1990's after Dr. Nick Christians at Iowa State accidentally
discovered its herbicidal properties while he was testing it for suppression
of turf diseases. After several years of efficacy studies and product
development, corn gluten meal has gained national attention as being
the first effective "organic" herbicide. Corn gluten meal
is not a registered pesticide because the U.S. EPA has granted an exemption
for corn gluten meal as an herbicide.
Corn gluten meal is a product of the wet milling process. It is a pre-emergent
herbicide which inhibits root formation during germination. It is currently
labeled for control of crabgrass, barnyardgrass, foxtails (Setaria
spp.), dandelion, lambsquarters, pigweed, purslane and smartweed. Data
suggest it has at least some activity on an even wider variety of plants.
It is safe to use on established turf. Do not use corn gluten
meal in an area in which you are trying to establish turfgrass.
Research shows 50-60 percent control can be achieved in the first year
when applied at 20 lbs. Per 1000 ft. Studies suggest that control is
improved in successive years and as use rates increase. Currently it
is sold as a dry product under various trade names, including Dynaweed,
Safe 'N Simple, Earth Friendly, W.O.W.!, Corn Gluten Meal Herbicide
and Propac. It is sold for the homeowner market in retail stores as
Concern-Weed Prevention Plus. Until recently it was only offered in
powder form. Now a granular form is available which can be more easily
applied with Vikon spreaders, rotary and drop spreaders. Application
rates vary from 12 to 20 lbs. per 1000 feet, once in early to mid-spring
and another in early to mid-August. Since the corn gluten meal is about
10 percent nitrogen, this catches two flushes of crabgrass and spreads
out the nitrogen effect. Two applications at 12 lbs/1000 ft. Will provide
nearly 2.5 lb. N/1000 ft per year. The nitrogen is in a slow release
form so there is little to no potential for foliar burn. Bulk orders
cost about $950/ton; 50 lb. Bags run between $25 and $30. This is the
same corn gluten meal sold at feed mills for animal feed; however, it
is pelletized for easier and more uniform application.
Portions of at least two proteins in the corn gluten meal, called peptides,
are the active ingredients in corn gluten meal. Laboratory studies show
the peptides themselves to be significantly more effective at preventing
weed germination than the corn gluten meal itself. Unfortunately the
peptides do not persist in the soil when used as a spray long enough
for effective control. Current research is aimed at isolating and packaging
these peptides to produce a sprayable product.
Source: John C. Stier, Turfgrass Extension Specialist, University
of Illinois
August
1999
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