the Fate of Field Paspalum Control - The Paginator

APPLIED RESEARCH
Controlling Smooth
Crabgrass in Tall Fescue
with Pre- and Postemergence Commercial Products
By Peter H. Dernoeden, Ph.D., and C. P. Ryan, Dept. of Plant Science and Landscape Architecture, University of Maryland
This field study, which was
conducted at the University of
Maryland Paint Branch Turfgrass
Research Facility in College
Park, compared all of the commonly
used preemergence herbicides that
target smooth crabgrass (Digitaria
ischaemum). In addition, corn gluten
meal (Espoma Corn Gluten 9-0-0)
was assessed and compared to the
commercial products. Finally, three
postemergence herbicides were applied
in late June and compared to the preemergence
herbicides and corn gluten
meal (CGM).
Our research methods
The turf was a mature stand of Titan
II tall fescue (Festuca arundinacea)
and was mowed two times weekly
to a height of 2.5 inches. Soil was a
Keyport silt loam with a pH of 5.7
and 2.2% organic matter.
Rates and dates of product applications
are noted in Table 1. The site
received rainfall or irrigation within
24 hours of each application. The
study site was irrigated thereafter to
avoid drought stress.
Turf color and quality were rated
once on May 13 using a 0 to 10 scale,
where 0 = entire plot area brown or
dead, and 10 = optimum green color
and density. Percent of the plot areas
covered with smooth crabgrass was
assessed visually on a 0% to 100%
scale, where 0% = no crabgrass, and
100% = entire plot area covered with
smooth crabgrass. Crabgrass ratings
less than 5% of plot area covered
(subjectively) were considered to have
provided commercially acceptable control.
Smooth crabgrass pressure was
uniform and severe across the site.
About CGM
Corn gluten meal, the protein fraction
of corn, is a natural herbicide that is
used to control crabgrass and other
weeds in “organic lawncare programs.”
Corn gluten was evaluated
previously by the University of Maryland
(Dernoeden, 2001). In those
studies, CGM applied twice per season
reduced crabgrass populations significantly,
but it did not provide commercially
acceptable control. Single applications
of CGM typically provided
poor control.
The product contains 9% to 10%
nitrogen (N) and, as such, also serves
as an N fertilizer. The recommended
use rate of CGM is 20 lbs. product
per 1,000 ft 2 . Hence, at this rate, a
manager is delivering 1.8 to 2.0 lbs.
N/1,000 ft 2 with a single application.
A single spring application of 2.0 lbs.
N/1,000 ft 2 , however, is considered
agronomically excessive and wasteful.
The sewage sludge Oceangro 5-5-0
fertilizer was entered into the study to
determine if this high rate of N (i.e.,
2.0 lbs. N/1,000 ft 2 ) from a natural
organic fertilizer would impact crabgrass
levels at the site. That is, the
Oceangro served as a standard for
comparing the potential influence of
organic N on crabgrass invasiveness in
the study site. The levels of N delivered
via CGM and Oceangro resulted in
excellent turf color and quality (8.8
22 MTC TURF NEWS