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ISSUE 11   JULY 15, 1999

 

DRY BEAN HERBICIDE APPLICATION TIMING
LIMITS AND CULTIVATION TIMING

    Delays in herbicide application in dry edible bean may have occurred due to frequent rain, windy
conditions, etc. The following are application timing limits for post-emergence herbicides based on
dry bean stage:

Pursuit, Raptor = Prior to flowering.

Assure II, Poast, and Select = 30 days or more before harvest.

Basagran = No crop stage restrictions.

    Refer to the herbicide label for other herbicide application timing considerations including weed size.
Also, consider the following label recommendations regarding the timing of between-row cultivation
following post-emergence herbicide application in dry bean:

Basagran = Do not cultivate within 5 days of application. Timely cultivation 2-3 weeks after application
may assist weed control.

Pursuit and Raptor = For maximum weed control, cultivate 7-10 days following application.

Assure II = Do not cultivate within 7 days after application as damage to the grass roots may result in
unsatisfactory control.

Poast = Do not cultivate within 7 days after application. Cultivating 7-14 days after treatment may help
season-long control.

Select = Cultivation of treated grasses within 7 days after application may reduce weed control.

Greg Endres
Extension Agronomist
Carrington R&E Center

 

CRISIS EXEMPTION DECLARED ON GRAMOXONE EXTRA

    North Dakota has declared a crisis exemption on Gramoxone Extra allowing North Dakota dry
and green pea producers to use the herbicide to control lamsquarters, nightshade, mustard, pigweed,
and mayweed as a preharvest application to minimize harvesting difficulties. The exemption will be in
effect from July 15, 1999, to September 15, 1999. A maximum of 10,000 acres in North Dakota can
be treated with a maximum of 1,875 gallons of product. The crisis exemption allows for a single application
at a rate of 1 to 1.5 pints per acre. For ground application, the product must be mixed in a minimum
of 20 to 40 gallons of water per acre. Aerial application requires a minimum of 7 to 10 gallons per acre.

    Non-ionic surfactant should be added at a rate of 1 quart per 100 gallons of water.

    Gramoxone Extra is a restricted use herbicide and may only be applied by licensed commercial
and private applicators. Applicators must follow all instructions, warnings and precautions on the
product label. A seven-day pre-harvest interval is required.

    Aerial application is prohibited within one mile of the city limits of any incorporated city or town and
any area comprised of ten or more inhabited, closely grouped residence.

    This is the seventh crisis exemption declared by ND this year. Twenty-nine section 18 applications
were submitted to EPA by the North Dakota Department of Agriculture during the 1999 growing season.
Three applications await EPA review.

 

1999 BEAN/OTHER CROP HERBICIDE UPDATE

Flexstar (Zeneca)
    Mode of action: PPO inhibitor
    a.i.:
fomesafen + adjuvant - Same as Reflex except no oil adjuvant
   Crops: Soybean
   Comments: Previously, use has been restricted in ND because of carryover to canola, sunflower
    and sugarbeet. Labeled in soybean at 1 pt/A in ND east of Interstate 29 from Fargo to SD border.
    Geographic region of use in soybean has been expanded in 1999 in ND to all areas east of Hwy 280
    (carryover increases as precipitation decreases) at a rate of 0.75 pt/A except for area east of Interstate
    29 mentioned above. Flexstar is same mode of action as Cobra and Blazer with excellent broadleaf
    weed control of several weeds but minimal to no crop leaf burn or speckling. Excellent control of
    ragweeds, vol sunflower, cocklebur, mustard, Venice mallow, and several other weeds. Weak on
    wild buckwheat. Do not use on dry bean - See Reflex.

Frontier (BASF)
    Mode of action: Acetamide (Mode of action unknown)
    a.i.:
dimethenamid and S-dimethenamid (active isomer).
    Crops: Possible registration in sunflower and potato.
    Comments: 3 to 4 weeks activity. Control foxtail and pigweed. Provides greater nightshade control
    than others acetanilides.

Frontier X2 (BASF)
    Mode of action: Acetamide (Mode of action unknown)
    a.i.:
S-dimethenamid (active isomer). 6 lb ai/A
    Crops: Same crops as Frontier.
    Comments: Use rates are 55% of Frontier rates. X2 will replace Frontier in future. Registration in
    potato and sugarbeet expected in 2001.

Novartis Chemical Co
    Mode of action: PPO inhibitor
    a.i.:
Unknown at this time
    Crops: Various transgenic crops
    Comments: Patented ‘Acuron’ gene will be inserted into different crops like corn to confer resistance
    to reduced risk PPO herbicides in development. PPO herbicides will have greater soil residue than
    one on the market. University trials in 2001. Transgenic crops to be developed are corn, sugarbeet,
    wheat, cotton, soybean, rice, canola, and sorghum. Acuron will be available in more than Novartis seed lines.

Poast (BASF)
    a.i.:
sethoxydim
    Crops: Several broadleaf crops.
    Comments: Price reduced to $8/gallon for 1999.

Quad 7 (AGSCO) - New adjuvant
    a.i.: Basic blend adjuvant classification.
    For use with Accent, Pursuit, and Raptor at 1% v/v. $14.75/gal.
    1% at 5 gpa = $0.75/A, 1% at 10 gpa = $1.50/A.
    May resolve some concerns regarding use of oil additives with herbicides such as Accent + Banvel
    on corn and precipitation problems with Betanex, Betamix, Betamix Progress.

Raptor (American Cyanamid)
    Mode of action: ALS inhibitor
    a.i.:
imazamox
    Crops: Imi canola, dry bean and field pea.
    Comments: The alternate name of Motive has been discontinued. The EPA granted a section 18
    specific exemption for the use of Raptor on dry beans for control of nightshades. Maximum of
    700,000 acres in North Dakota (except the southwest district) Applications from May 1-June 30.
    Ground application only at 4 fl oz formulated product per acre. One application per crop season.
    Preharvest interval of 60 days.
        Soybean yellowing in 1999 may be due to hot, humid conditions at applications, not using Fe
    chlorosis tolerant varieties, stresses from excessive rain and hot dry soil surface which limited root
    depth and development, and from late applications. Section 18 registration on Imi canola has been
    granted. Section 18 for dry beans and field pea at 4 fl oz/A is pending. For use on crops other than
    soybean - NIS with or with out nitrogen fertilizer. No oil adjuvants allowed. Residue trials on Imi
    tolerant sunflower planned for 1999 to allow use in 2000 through Section 18 registration has been
    postponed for one year. Tolerance to Imi sunflower lines will be researched in 1999. Weak on wild
    buckwheat, Venice mallow, biennial wormwood, common ragweed and essentially no control of
    perennials.

Reflex (Zeneca)
    Mode of action: PPO inhibitor
    a.i.:
fomesafen - Same as Flexstar except without oil adjuvant
    Crops: Soybean. A ND Section 18 was submitted for nightshade control in dry beans but was later
    retreacted due to clearance of Raptor Section 18.
    Comments: Previously, use has been restricted in ND because of carryover to sugarbeet. Labeled
    in soybean at 1 pt/A in ND east of Interstate 29 from Fargo to SD border. Geographic region of use
    in soybean has been expanded in 1999 in ND to all areas east of Hwy 281 at a rate of 0.75 pt/A except
    for area east of Interstate 29 mentioned above. 1999 Section 18 submitted for use in dry bean for use
    in same area as soybean. Data from MI indicates less dry bean crop injury than Basagran. E control
    of ragweeds, volunteer sunflower, cocklebur and several other weeds.

Rezult (BASF)
    a.i.:
bentazon +sethoxydim
    Crops: Soybean and possibly dry beans and field pea
    Comments: Price reduced to approximately $14/A - cheaper than Basagran alone.

Select (Valent)
    a.i.:
clethodim
    Crops: Registered on chick pea/garbanzo bean under dry bean label.

Topsite 2.5G (American Cyanamid)
    Mode of action: ALS inhibitor + photosynthetic inhibitor
    a.i.:
imazapyr (0.5%) + diuron (2%)
   Crops: Noncropland and bare ground weed control
   Comments: Same ingredients as in Sahara 70WDG but formulated as a granular for convenient
    application. Diuron will control ALS resistant kochia. Used as a preemergence or early postemergence
    will control over 100 annual and perennial grasses and broadleaf weeds. Requires precipitation
    after application for maximum control. Rate is 200 to 300 lb/A/0.5 to 0.7 lb/100 sq ft.

Touchdown 5E (Zeneca)
    Mode of action: EPSP synthase inhibitor
    a.i.:
Trimethyl sulfonium salt of glyphosate (NOT sulfosate).
    (Same active ingredient as Roundup but a different salt.)
    Roundup/Ultra/RT = glyphosate - isopropylamine salt
    Touchdown = glyphosate - trimethyl sulfonium
   Crops: Burndown for corn and soybean, and wheat. Use on Roundup Ready soybean and
    corn pending.
   Comments: Previously registered only in noncrop uses. Negotiations with Monsanto will allow
    Touchdown on most Roundup Ready crops in future. Touchdown 5E contains adjuvants as Roundup
    Ultra but does not restrict addition of additional adjuvants. Touchdown is affected by water quality
    and salt antagonism as Roundup Ulta. Some observations that Touchdown may temporarily injure
    some varieites of Roundup Ready corn and canola. Observations may be caused by the phytotoxic
    effect of the TMS salt as compared to the DMA salt of Roundup brands.

Richard Zollinger
NDSU Extension Weed Specialist
rzolling@ndsuext.nodak.edu

 

HERBICIDES AND WEATHER TANGO TOGETHER

    Herbicides are influenced by weather. Weather factors that influence herbicide applications are
wind speed and direction, temperature, relative humidity and rainfall. Wind speed and direction as well
as lapse rate and inversions affect aerial and ground applications of herbicides even with properly
selected and calibrated equipment. The main concern is spray drift, especially during inversions and
lapse rate change during or after an application. Also, high temperatures and low relative humidity
will evaporate spray droplets in flight to target locations and will increase the drying of the droplet
on the weed leaf surface. Herbicide application is best when temperature and relative humidity are
moderate.

    There are both direct and indirect effects of weather on the performance of herbicides. Directly,
weather may reduce the effectiveness of herbicides, especially contact chemicals, by rainfall reducing
the effectiveness of the herbicide when rain occurs within four hours (or other chemical specific rain-fast
time interval) after application. Also, a windstorm that can blow treated soil from the top of bedded
fields sprayed with soil-applied herbicides and deposit the soil into furrows can also limit effectiveness
of the herbicide. Contact herbicides work best when the weather is hot and sunny. Hormone herbicides
and most other post-application chemicals perform best when the weather is ideal for weed growth.
Preemerge herbicides are usually more effective if rainfall occurs within a week or so after application
(or sooner on the newer rain-activated herbicides). Soil incorporated herbicides usually perform well
over a wide range of conditions and usually are more weather-proof, as long as cool soils do not limit
activity on weeds or increase crop injury or crop stunting.

    Weather also strongly influences the persistence of most herbicides. Generally, a herbicide will persist
longer under cold, dry climates than under warm, moist conditions. However, carry-over problems vary
greatly among herbicides. Chemical formulation (example: salt versus ester), water solubility, molecular
weight (influences volatility), volatility, photodecomposition and microbial breakdown will determine the
persistence of each herbicide.

    Consider the weather previously affecting weed and crop growth as well as the weather at the time of
application and after application in order to determine the best timing and herbicide for weed problems.

Denise A. McWilliams
Extension Crop Production Specialist
dmcwilli@ndsuext.nodak.edu


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