Tuesday, April 28, 2009

Chute "N" The Bull

With the tight profit margins agricultural producers face, the need to
control input costs is greater than ever. As input costs rise, we
naturally try to reduce these costs whenever we can. One cost-cutting
approach producers often ask about is reducing herbicide rates,
sometimes to below the minimum listed on the label. It is an option, but
consider these pros and cons before taking this approach to cutting
• There is the potential for saving up to 50 percent of the herbicide
cost per acre depending on the species of weeds present and their
herbicide susceptibility. For low rates to be effective, the weeds must
be a highly susceptible species and be treated when they are very small.

• Low rates may reduce the potential for adverse environmental impacts.
• Because low rate applications must be made early when the weeds are
small, the potential for later weed flushes that would require a second
application increases.
• Careful scouting is required to identify the weed species and estimate
their density before they get too large. Producers must invest the time
to get out and walk their fields and pastures to see the small weeds.
• The application window is very short to treat the weeds while they are
small and susceptible. Any delays caused by wind, rain or other
conflicts can allow the weeds to get too large to be controlled by a low
• Small weeds are more susceptible to herbicides, but since the target
crop is smaller, it may also be more susceptible to herbicide injury.
• The cost savings are only for the herbicide. The application cost
remains the same regardless of herbicide rate.
• The potential for a control failure is higher with below-label rates.
Chemical manufacturers conduct tests over a wide range of environments
and select rates they believe will provide the most consistent
performance. If a below-labeled rate is used and a failure occurs, the
producer assumes all of the liability.
• In cases where a failure occurs, the surviving weeds can go to seed
and recharge the seedbank to become future weed problems.
• Only highly susceptible weed species will be controlled at low rates.
Less susceptible species listed on the label may not be controlled and
will continue to pose problems.
An additional concern is the potential development of herbicide
resistance. In some cases, the use of low herbicide rates has selected
for individual weeds within a species with some herbicide resistance.
Those surviving plants then reproduce and their resulting progeny have
an increased level of resistance. In one experiment using several rates
of a known herbicide on susceptible ryegrass, there were plants that
survived the low rate application. These plants were then allowed to
reproduce, and, within four generations, a completely
herbicide-resistant population developed. If you suspect herbicide
resistance, switch to a herbicide with a completely different mode of
action that is labeled for the weed and use the full, labeled rate.
Another issue is the legality of using below-label rates. The rates
listed on herbicide labels are approved by the EPA and any application
above those rates is illegal. However, some state officials say that a
user can legally choose a rate lower than listed on the label unless the
label specifically prohibits lower rates. It is best to check with your
state department of agriculture to find out if they consider below-label
rate applications a violation.
Use of low rates is an option to consider in certain situations, but it
carries significant risks that the producer must be willing to accept.
The producer must decide if the potential cost savings is worth
accepting the associated risks. You can find this and past articles on
the web at www.mycountrytractor.com for your reference. Extension
programs serve of all ages regardless of socioeconomic level, race,
color, sex, religion, disability, or national origin. The Texas A&M
University System, U.S. Department of AgriculturCommissioners Courts of Texas Cooperatings serve of all ages regardless
of socioeconomic level, race, color, sex, religion, disability, or
national origin. The Texas A&M University System, U.S. Department of
Agriculture, and the County Commissioners Courts of Texas Cooperating.

Tommy Neyland, CEA-Ag
Texas Agrilife Extension Service