Although it is only January, it has been
a mild winter with a severe lack of rain in the desert southwest. Typically,
there will likely be some precipitation during February and March that can result
in early germination (mid to late March) of many summer grassy weeds such as
cupgrass, crabgrass and watergrass (junglerice or barnyardgrass). This update
will discuss preemergence weed control options in overseeded, non overseeded
and native areas for grassy and broadleaf species as well as a tip on
postemergence control of troublesome winter weeds.
weed control for grassy weed species in the desert southwest
Weeds such as cupgrass,
crabgrass and watergrass generally will
begin germinating in mid to late March
and that means the preemergence herbicide application window is only a few
short weeks away. If the bermudagrass was healthy prior to overseeding and
plant samples in the field reveal healthy stolons and rhizomes then move forward
with products such as prodiamine, dithiopyr or pendimethalin. For non overseeded and native areas, some turf
managers are using alternatives such as simazine and oryzalin. Newer products
such as flumioxazin can control grasses as well as some broadleaved weeds.
weed control options where bermudagrass health is poor
The chemical options
discussed above can be detrimental to the ability of the bermudagrass to
recover where turf health is poor. In such cases, an alternative, although more
expensive option is oxadiazon. Oxadiazon will not inhibit the ability of the
bermudagrass stolons to establish in the soil and can be applied safely on
ryegrass in the granular form.
preemergence weed control
The smart option for
broadleaf weed control in overseeded, non-overseeded and native areas is isoxaben.
Isoxaben will control (or suppress) many common broadleaf weeds in the
southwest that will be germinating within the next 6-10 weeks such as Russian Thistle,
purslane, plantain, fleabane and spurge.
control of winter weeds
If the preemergence
window for grassy and broadleaf weeds was missed in the fall season, act now to
remove pesky winter weeds before they mature and outgrow their ability to be
controlled with herbicides. Several combination herbicide products such as
combinations of 2,4-D, MCPP, and dicamba or 2,4-D, dicamba, carfentrazone and
mecoprop will control common mallow, London rocket, and mustards that are
common winter weeds in the desert southwest.
Preemergence weed control in most cases will be more
efficient and cost-effective when compared to postemergence management. Plan
now and be prepared to apply the appropriate chemicals prior to grassy and
broadleaf weed germination during mid to late March.
A special thank you to Kai Umeda, Area Extension
Turfgrass Specialist with the University of Arizona for his assistance with
Source: Brian Whitlark (firstname.lastname@example.org)
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