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Top Seven Reasons Pasture Weed Control
Programs Don’t Work
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By Eddie Funderburg, Ph.D.
The best chance to weed control success lies in
minimizing the incorrect ways. In this article, I want to identify and
briefly discuss the top seven reasons that pasture weed control programs
don’t work as well as they should. A popular comedian has a top 10 list
for his act, but since I’m only about 70 percent as funny, I only have a
top seven list.
No. 7 – Spraying too early
Many times ranchers spray for weeds at a specific
date on the calendar, May 1 for example.
This works most of the time. However, what happens
if the weather is not exactly average that year? If it’s colder than
average that spring, the weeds may not yet have emerged when you spray.
You can miss them altogether by spraying too early when the weeds are
not there yet.
The solution is obvious; scout the fields and spray
the weeds at the proper time based on stage of growth of the weed.
No. 6 – Misidentification of the weed
All weeds are not created equal in their willingness
to die from a herbicide program.
Try as you may, you’re not going to kill a grass or
sedge with 2, 4-D unless you set the container on top of it and leave
it.
Among broadleaf weeds, some tough weeds to control
are more susceptible to different products. Scout your fields and learn
to identify the weeds. If you don’t know what one is, ask someone who
does.
After you’ve properly identified the weed, find a
herbicide that controls it.
No. 5 – Bad environmental conditions
Control declines precipitously on almost all weeds
when they are in drought stress. The plants are merely trying to survive
and are not actively growing and taking up the herbicide in drought
conditions.
While it may never be too dry to spray, it can be
too dry to get good results. In addition to soil moisture, pay attention
to wind speed and direction to control off-target drift.
Life is much simpler when you kill weeds on your
property and avoid killing the neighbor’s garden.
No. 4 – Sprayed at the wrong growth stage
Most weeds are best controlled when they are young
and actively growing. When they get larger, it takes more herbicide to
kill them and control is much more erratic.
Horsenettle and blackberries are an exception.
Control of both of these is best when they are in full bloom or have
fruit on them. Spraying them too early results in a top kill, but
regrowth usually occurs.
Read the label carefully to determine timings for
specific weeds.
No. 3 – Used the wrong product
Often, the cheapest herbicide will do as well as
anything else. The conditions where this is true are when the weeds fall
into the easy-to-control category and conditions are ideal for control.
For difficult to control weeds (Sericea
lespedeza and horsenettle for example), more expensive
chemicals are usually needed.
Cheap herbicides can be good if you do an
excellent job of observing the cautions listed previously in this
article, but may not work if conditions are less than ideal.
No. 2 – Didn’t calibrate sprayer
I don’t think it’s an exaggeration to say that
the majority of ranchers don’t calibrate their sprayers.
Calibrating a sprayer should be done every
season.
Calculating the volume you spray is critical to
knowing how much product to put into the tank.
When you calibrate, also inspect nozzles,
screens, lines, pump, etc. to make sure everything is okay.
A calibration method for boom type sprayers can be
found at
http://www.noble.org/Ag/Soils/BoomSprayerCalibration/CDIndex.pdf
and a calibration method for boomless sprayers can be found at
http://www.noble.org/Ag/Soils/BoomlessSprayerCalibration/CDIndex.pdf.
No. 1 – Didn’t read the label
Reading the label covers all previously mentioned
points. The label covers safety considerations, product use, container
disposal and any other information about the product you need to know.
Failure to follow directions can not only lead to poor weed control, it
is also a violation of federal law.
Following the directions on the herbicide label is
about the closest I can get to guaranteeing weed control.n
Eddie Funderburg is a soil and crops specialist with The Samuel Roberts
Noble Foundation, Ardmore, Okla.
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