Vol. 51—1997 - NorthEastern Weed Science Society

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when preemer~ence herbicides are applied for summer annual weeds,
such as crabgrass and goosegrass. Commonly, herbicides in the
dinitroanalige class are used for this purpose for well-known
reasons. These herbicides work by inhibition of cell division.
With certain lof these herbicides, new stolons of bermudagrass may
be inhibited/from establishment because of inhibition of root
penetration ~nto treated soil. If nematodes are also present,
the scenariolfor interaction or added detrimental effects is set.
In fact, it ijas been observed that some bermudagrass was not
recovering f~om nematicide treatment, even when the treatment
apparently i*hibited nematodes by assaying the soil for their
numbers fol19win9 treatment. In questioning management practices,
dinitroanili*e herbicides were used in many cases.
Experim~nts were conducted in the field to examine the
possibility that herbicides were involved in a detrimental
interaction tith nematodes. Sites were used that had natural
infestationsjof sting nematodes; counts taken prior to initiating
experiments ~howed averages of around 30 nematodes/lOa cc of
soil, consid¢red a moderate infestation. Experiments were
conducted on! a golf course fairway or on a sod farm in the
region. The I first site was common bermudagrass, and the second
was Tifway bermudagrass. Herbicide treatments included
priodiamine,l at 1.0 Ib a.i./acre (1.5 Ib Barricade 65WG),
pendimethalip, at 3.0 Ib a.i./acre (5.0 Ib Pre-M 60DG) ,
oxadiazon, a~ 4.0 Ib a.i./acre (200 Ib Ronstar G), and dithiopyr,
at 0.5 Ib a.~./acre (2 qt Dimension lEC). Plots not treated with
herbicides ~re also used. Within herbicide treatments, in a
standard spl~t-plot design, nematicide treatments were applied.
These inclu~d ethoprop, at 20 Ib a.i./acre {200 Ib Mocap lOG},
fenamiphos, ~t 10 Ib a.i./acre (100 Ib Nemacur lOG), or plots
that were ndt treated with nematicide. Herbicide were applied in
late Februa~ or the first week in March, and nematicides were
applied in ~id-April. Turf quality (0-9 scale, with 9 being
best) was r~ted in all plots throughout the summer. Also, turf
cores were 9aken to about 20-cm depth, and roots extracted and
measured. j
ResultJ of these experiments indicated that the turf
response to/treatments, as measured by turf quality, varied among
the treatme*ts. Usually, the bermudagrass responded to
nematicide ¢reatments, with fenamiphos treatment having a greater
efficacy th*n ethoprop. There was usually very little difference
in spring gfeenup among plots, although in one year, plots
treated wit~ pendimethalin were delayed in greenup and in the
next year, flots treated with oxadiazon were delayed in greenup.
In both cases, noticeable effects only remained about 2 weeks. In
early and mid-summer ratings, there was little difference among
herbicides,jbut in August ratings, plots treated with oxadiazon
and fenamip~os had significantly better turf quality than other
treatments. I In 1995, fresh root weights measurements and root
length meas4rement were greater in oxadiazon-fenamiphos plots
compared tol pendimethalin-fenamiphos plots. Considering only
nematicide ~reatments, fenamiphos treatments increased root
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