Vol. 54—2000 - NorthEastern Weed Science Society

POSTEMERGENCE SMOOTH CRABGRASS CONTROL
EVALUATIONSINMARYLAND,I998-1999
P. H. Demoeden and J.M. Krouse'
ABSTRACT
Three studieswere conductedto evaluate herbicidesfor postemergence smoothcrabgrass (Digitaria
ischaemum [Schreb.]Muh!.)control inmature stands ofperenniaJryegrass (Lo/iumperenne). The objectives
of the three studieswere as follows: I) to assess Acclaim Extra(fenoxaprop)and Daconate 6 (MSMA) tankmixes
as a possible resistance management strategy for crabgrass; II) to compare the crabgrass control
effectiveness of Acclaim Extra and Drive (quinclorac) to PreClaim (fenoxaprop + pendimethalin) applied
in early and mid-postemergence application timings; and III) to compare multiple, low rate, application
timings of Acclaim, Acclaim Extra, and Prograss (ethofumesate) for crabgrass control efficacy. Drive was
tank-mixed with methylated seedoil (1% v/v) in all studies. Herbicideswere applied in SOgpa with a CO 2
pressurized (35 psi) backpack sprayer equipped with an 8004E Tee Jet nozzle. All sites were irrigated 24
hrs prior to each herbicide application and thereafter to prevent wilting of the turf. Plots were 5 by 5 ft and
were arranged in a randomized complete block with four replicates. Percent of plot area covered with
crabgrass was assessed in mid-to-Iate August using a visual 0 to 100% linear scale where 0 = no crabgrass
and 100 = entire plot area covered with crabgrass. Data were subjected to analyses of variance and
significantly different means were separated by the least significant different t-test (P = 0.05).
In study I. there were two application regimes: I) sequential applications at 1- 2 leaf(L) + tillering
(T) stages, and 2) a single application at tillering. Data showed that only plots treated sequentially with
Acclaim Extra alone (0.04 Ib ai/A = IblA); 1-2L + 1) provided excellent control (