ISSUE 7 JUNE 17, 1999
LIMITS ON LATE WILD OAT HERBICIDE APPLICATION IN WHEAT
Delays in controlling wild oat in wheat have occurred due to adverse weather
conditions. The following are the
wheat and wild oat stage limits for POST herbicides:
|Wheat Wild oat|
|Assert:||Up to joining||4-leaf|
|Avenge:||Prior to flag leaf emergence||5-leaf|
|Achieve:||Up to boot||6-leaf|
|Puma:||6-leaf (prior to jointing)||2-tiller|
|Tiller:||Up to 6-leaf (HRS only)||2-tiller|
|Cheyenne:||End of tillering or 6-leaf
|Hoelon:||Up to 4-leaf||4-leaf|
Refer to herbicide labels and NDSU Extension Service circular W-253 '1999 North
Control Guide' for required information on use.
Carrington R&E Center
CROP-PROD AND OTHER MIRACLE ADDITIVES
Crop-Prod is being represented as enhancing herbicide activity - to
the point that herbicide
rates can reduced far below labeled use rates (66%). Reports are that performance of wild oat
herbicides with Crop-Prod are good.
What is Crop-Prod?
Nitrate nitrogen 0.525%
Ammonium nitrate 2.625%
Urea nitrate 0.350%
Phosphoric acid 3.5%
Total = 10.5 lb/gal
Cost = $0.60/fl oz or approximately $75/gallon.
The question to ask is why OR who really should get the credit for
excellent herbicide activity - Crop-Prod
or the environment.
The Rest of the Story Realize that ALL herbicides are showing
high activity and weed control this
year. Environmental conditions of abundant rainfall and moderate temperatures have caused plants to be
more susceptible to herbicide activity. A case to demonstrate this is with Achieve herbicide. In the past 4 to
5 years of testing in NDSU research trials, wheat did not show any injury from Achieve. In 1999, Achieve
in tank-mix with bromoxynil and ammonium sulfate fertilizer has caused slight to severe wheat injury which
was surprising. Some growers have reduced the rate of Achieve and have found excellent weed control
and greater wheat safety. This spring growers have reduced herbicide rates of many other herbicides and
have found good weed control. This year in our NDSU research plots with herbicides at 1/4 to 1/3 of labeled
use rates we have found excellent weed control. Summary - Herbicides are working very well this year.
Crop-Prod contains 3.5% by weight nitrogen fertilizer in three
forms. Use of nitrogen fertilizer either as
urea-ammonium sulfate or 28% liquid nitrogen is a general recommendation with many herbicides to
overcome hard water antagonism and promote absorption into plants. Since Crop-Prod contains nitrogen
it is not surprising that enhanced herbicide activity results when added to herbicides. However, supplies
of liquid nitrogen solutions available form local dealers is between $3.50 to $4.00 gallon. Is the rest of the
ingredients in the jug worth the extra $71 for the Crop-Prod? Also, salts with a positive charge in water,
such as iron, magnesium antagonize herbicides. Even though these salts are in low concentration in
Crop-Prod, why add antagonists to your spray solution that may decrease weed control?
In conclusion, some people may attribute excellent weed control from
the Crop-Prod added to the
herbicide when actually Mother Nature should get the credit. The real "proof of the pudding" would be to
apply herbicides at reduced rates with Crop-Prod under drier, less ideal conditions and observe weed
control. Or better yet, spray part of the field with the herbicide of choice plus Crop-Prod and for the other
part of the field substitute inexpensive 28% liquid nitrogen or ammonium sulfate for the Crop-Prod and
see if there is a difference. Also, if claims are made that herbicide rates can be reduced below label
rates - have the representative sign their name to that claim.
EFFECT OF SUNLIGHT AND TEMPERATURE ON HERBICIDE ACTIVITY
Sunlight inactivates some herbicides by ultra violet (UV)
light. Trifluralin and Eptam degradation is
minimal because incorporated is done soon after application. Achieve, Poast, and Select are highly
sensitive to UV light and will degrade rapidly if left in nonmetal spray talks for an extended period of time
or if applied during mid-day. To avoid UV breakdown, apply Achieve, Poast, and Select soon after
mixing, after 4:00 pm, and with superior oil adjuvants, like DASH and MSO type. Apply Achieve
with Supercharge adjuvant that is included with the product.
Ideal temperatures for applying most POST herbicides are
between 65 to 85 F. Most weeds are
killed slowly below 60 F. Some herbicides may injure crops if applied above 85 F. Avoid applying
volatile herbicides such as 2,4-D ester, MCPA ester and dicamba during hot weather, especially near
susceptible broadleaf crops, shelterbelts, or farmsteads.
Cold temperatures cause concern for crop safety and possible reduced
weed control. Plants degrade
herbicides by metabolism but plant metabolism slows/stops during cool/cold conditions which extends the
amount of time required to degrade herbicides in plants. Rapid degradation under warm conditions allow
crop plants to escape herbicide injury. However, cold temperatures after herbicide application increases
time necessary for degradation of the active ingredient and this may increase crop injury.
Temperatures following herbicide application determine crop safety
or injury. Continued cold night and
day temperatures cause metabolism to shut-down in plants preventing herbicide degradation. However,
herbicides may be sprayed following cold night-time temperatures if day-time temperatures warm to at
least 60 degrees.
Wild oat is a cool season grass and is more sensitive to Hoelon and
products containing fenoxaprop
(Dakota, Tiller, Cheyenne, and Puma) during cool rather than warm or hot conditions. Green and yellow
foxtail are warm season grasses and may shut-down under cold conditions resulting in reduced control.
Many broadleaf weeds are warm season plants and are controlled better during warm/hot conditions
under active plant growth with sufficient moisture.
Some ACCase inhibitors, primarily Hoelon and fenoxaprop (Dakota,
Tiller, Cheyenne, Puma) may
cause crop injury and give greater weed control when cold temperature follow application. Both Hoelon,
and fenoxaprop are more active on grass weeds during cold temperatures. Relative crop safety is much
greater from Hoelon than fenoxaprop so treating with Hoelon in cool/cold conditions is generally beneficial.
Other herbicides, such as Assure II, Poast, Fusilade DX, and Select
will not cause injury to broadleaf
crops but may provide equal or better grass control in cool rather than warm weather.
Cold temperatures following application of ALS herbicides may
increase crop injury with little effect
on weed control. Pursuit, and Raptor on beans, Accent, Matrix in Basis, Basis Gold and Accent Gold,
and Pinnacle in Basis in corn, Lightning on Imi corn, FirstRate on soybeans, Bladex in corn, Sencor/Lexone
in legumes and potatoes, and bromoxynil in grass crops all have shown significant corn and wheat leaf burn
when freezing temperatures follow application.
Basagran, Blazer, Cobra, Flexstar, Liberty, Stampede, and Gramoxone
Extra may not cause crop injury
but less weed control may result when cold temperature follow application.
2,4-D, Banvel/SGF, Clarity, MCPA, Stinger, Starane, Roundup/
Touchdown (glyphosate) have
adequate crop safety and provide similar weed control but the speed at which weeds die may be slow
when cold temperature follows application.
Recommendations for applying Hoelon, fenoxaprop based herbicides,
ALS herbicides, Bladex, and
Sencor/Lexone is to delay application until daytime temperatures exceed 60 degrees F and after active
plant growth resumes.
Adjuvant use may also affect crop safety and weed control. Oil
additives may increase risk of crop
injury but may be necessary for greatest weed control. Refer to each herbicide label for specific information
on adjuvant use during stress conditions. Use an oil additive if risk of crop injury is acceptable for those
herbicides that allow oil additives.
NDSU Extension Weed Specialist
LABELS LIMIT SPRAYING FOR POST APPLICATIONS IN CORN
Use of postemergence corn herbicides dictates knowing when to apply
the herbicides. Limitations
on harvest intervals between when you spray and when you may harvest must also be kept in mind.
Remember the label will provide you all of this information. Much spraying has been occurring in the
Valley over the last two weeks. Keep in mind that many herbicides work better under the humid
conditions we have been experiencing recently. Also, cool nights will slow down the metabolism of the
herbicides through the corn plants and may limit the harmless breakdown of the absorbed chemicals in
the corn plant causing weakening or stunting of corn in some cases on certain herbicide modes of activity.
As corn gets taller, remember to be careful with sprayer nozzle positioning for those herbicides that can
be used later by spraying with drop nozzles. Morning applications can increase herbicide activity (or
cause slight corn injury especially after cold nights) by the morning dew on the corn plant along with
the upright leaf structure of the plant allowing chemical to funnel and run directly down into the corn
plant whorl. Some general application restrictions include:
Bromoxynil may be applied to corn up until tasseling;
Bromoxynil + Atrazine may be applied on corn up to 12 inches tall;
Basagran may be applied on corn at all stages, but weed size limits use;
Atrazine + oil may be applied before corn is 12 inches tall;
Bladex/Cy-Pro may be applied up to corn in the 4-leaf stage;
Sencor can be applied up to tasseling;
2,4-D can be applied up to tasseling but use drop nozzles once corn is over 8
inches tall and remember
to use amine formulations when temperatures approach 80 to 85 F to limit chemical movement;
Shotgun can be applied up until corn has 5 leaves or is 12 inches tall, whichever is first;
Banvel/Clarity can be applied up to 15 days before tasseling, but use drop nozzles
once corn is
8 to 36 inches tall (and if soybeans are nearby and over 10 inches tall or have begun to bloom, dont
apply either herbicide to corn over 24 inches--this also applies to Celebrity B and NorthStar);
Banvel/Clarity + Atrazine can be applied up to 5-leaf corn;
Distinct can be applied to corn up to 24 inches tall;
Stinger can be applied on corn up to 24 inches tall and watch weed size limitations;
Curtail can be applied to corn up to 8 inches tall or once 4 visible leaf collars are showing;
Scorpion III can be applied to corn up to 8 inches tall;
Basis can be applied from the spike to the 4 leaf (or 2 collar) stage in corn;
Basis Gold can be applied to corn up to 12 inches tall or prior to 6 collars in corn;
Accent can be applied on corn up to 20 inches tall or with 6 or fewer collars;
Accent + Atrazine can be applied on corn up to 12 inches tall;
Accent + Banvel/Clarity can be applied to corn up to 8 inches tall broadcast and
to 24 inches with drop nozzles;
Celebrity can be applied on corn up to 20 inches or with 6 or less collars and
applied with drop
nozzles from 20 to 36 inches;
Accent + Bromoxynil can be applied on corn up to 20 inches or 6 collars and with
from 20 to 24 inches;
Accent + Hornet can be applied up to 20 inches or 6 collars on corn and with drop
from 20 to 24 inches;
Accent + Scorpion III can be applied up to 8 inch corn and with drop nozzles from 8 to 24 inch corn;
Accent Gold can be applied on corn up to 20 inches or with 6 or less collars and
with drop nozzles
from 20 to 24 inches;
Permit can be applied on corn up to 24 inches tall broadcast and with drop nozzles from 24 to 36 inches;
Tough can be applied on corn up to 68 days prior to harvest;
Aim can be applied on corn up to 12 inches tall or up to 8 collars;
Leadoff can be applied on corn up to 8 inches tall.
Denise A. McWilliams
Extension Crop Production Specialist