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ISSUE 5   June 4, 1998


MERGER OF CHEMICAL COMPANIES

Monsanto and American Home products entered into a definitive agreement to combine companies. The new company will have a new name and the agricultural portion of the business will be headquartered in St. Louis, MO.


HERBICIDE USE DURING COLD WEATHER

    Cold temperatures cause concern for crop safety and possible reduced weed control. Some herbicides are broken down in plants by metabolism but plant metabolism slows/stops during cool/cold conditions which extends the amount of time required to degrade herbicides. Rapid degradation under warm condition allows crop plants to escape injury from herbicides. However, cold temperatures after herbicide application lengthens the time for degradation and results in crop injury.

    **Note** It is the temperatures that follow herbicide application that 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.

    Another consideration is weed response to herbicides under different temperature regimes. Wild oat is a cool season grass and is more sensitive to Hoelon and fenoxaprop based herbicides (Dakota, Tiller, Cheyenne, and Puma) during cool rather than warm or hot conditions. Green and yellow foxtail are warm season grasses and shut-down under cold conditions resulting in reduced control. Many broadleaf weeds are warm season plants and greater weed control occurs during active plant growth during warm/hot conditions with sufficient moisture.


Herbicides that cause crop injury and give greater weed control when cold temperature follows application
:

    (See page 110-111 of the 1998 North Dakota Weed Control Guide, numbers in ( ) represent modes of action based on classification listed)

    ACCase inhibitors (1):

    Primarily fenoxaporop based products (Dakota, Tiller, Cheyenne, Puma).

    Hoelon, as fenoxaprop, is more active on grass weeds during cold temperatures. However, relative crop safety is much greater from Hoelon than fenoxaprop so risk crop injury is less when cool/cold temperature follow application.

    Other herbicides, such as Assure II, Poast, Fusilade DX, and Select will not cause crop injury but may provide equal grass control as compared to warmer weather.

Herbicides that cause crop injury with little difference in weed control when cold temperature follows application:

ALS Inhibitors (2):
Pursuit, 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 (5) in corn.
Sencor/Lexone (5) in legumes and potatoes.
Buctril (6) in grass crops.

Herbicides that may not cause crop injury but less weed control may result when cold temperature follows application:

Basagran (6), Stampede (7B), Liberty (10), Cobra , Blazer, and Flexstar, and Gramoxone (22).

Herbicides with adequate crop safety and similar weed control but the speed at which weeds die may be slow when cold temperature follows application:

Plant growth regulators (4) Such as 2,4-D, MCPA, Banvel, Stinger, Starane.
Roundup/Touchdown (9).

    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 directions 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.


NEW SECTION 18 CRISIS EXEMPTIONS CLEARED

    Herbicide 273 has received crisis exemption clearence for use in canola for control of smartweed in the following counties of North Dakota: Towner, Pembina, Cavalier, Walsh, and Ramsey, and for control of wild buckwheat in Hettinger, Bowman, Slope, and Adams counties of North Dakota.

    Apply Herbicide 273 at 2 to 3 pt/A early post-emergence to canola 2 to 6 inches tall at 10 to 20 GPA by ground or 2 to 15 GPA by air. Temporary burning and canola injury may occur if applied in temperature greater than 80 degrees F. Temperatures of 60 to 80 degrees F are recommended for application.

    Do not use any adjuvants with H 273. Any crop can be planted the year following application. The label must be in the possession of the user at the time of application. The label expires on July 31, 1998.

    Paramount has received crisis exemption clearence for use in wheat for control of volunteer flax in the following counties of North Dakota: Ward, Renville, Bottineau, and McHenry. Apply Paramount at 0.17 lb/A postemergence

    Refer to label for crop stage, flax stage, GPA, tankmixes, adjuvant use, or other restrictions. Do not plant flax or lentils for 22 months following application. For all other crops, a rotation of 10 months is required. Do not allow Paramount to drift onto flax crops. Do not apply by aerial application. The label must be in the possession of the user at the time of application. The label expires on June 11, 1998.

    Stinger has been granted Section 18 Emergency Exemption use of Stinger in North Dakota for weed control in canola. The herbicide is labeled at 1/3 to 1/2 pint per acre for Canada thistle and 1/2 pint per acre for perennial sowthistle control. Recommended height for treatment of Canada thistle and perennial sowthistle is four- to six-inches.

    North Dakota State University data indicates that Stinger also provides good to excellent control of common cocklebur, marshelder, common ragweed, annual smartweed, and sunflower. Also, Stinger is rated by NDSU as fair to good for control of wild buckwheat and black nightshade.

    Apply Stinger with ground equipment using a total spray volume of 10 to 20 gallons per acre. Do not apply within 72 days of harvest. Refer to the label for other details. Cost is about $20 to 30 per acre.

    Research conducted at NDSU Research Extension Centers in 1996-97 at Minot and Carrington indicates good canola tolerance to Stinger applied at 0.33 pint per acre. Also, canola tolerance and foxtail control was excellent with Stinger plus Poast or Assure II tank mixtures.

    No decision has been made regarding Muster on canola. ND Dept of Ag is not allowed not declare a Section 18 Crisis Exemption because Muster is not labeled on any other crop in the U.S.

No decision has been made on Motive in Imi canola.

Richard Zollinger
NDSU Extension Weed Specialist


POSTEMERGENCE WEED CONTROL OPTIONS IN FIELD PEA AND LENTIL

    The warm weather in April has allowed the majority of pea and lentil acres to get in early. Dry top soil conditions has resulted in concern with pre-plant herbicides that were applied with minimum or no incorporation having reduced performance. The warm spring has also resulted in most weed species to begin to emerge. Pea and lentil growers could be very reliant on postemergent herbicides this growing season.

    Field pea and lentil are not very competitive with weeds and spraying early postemergence is very important. Most broadleaf herbicides require small weeds and small peas or lentils to reduce the injury potential to the crop. Also, with most broadleaf herbicides do not apply above 85 F or when the peas or lentils are under heat/drought stress. Keep in mind with postemergent weed control options for field pea and lentil that many herbicides might unfamiliar to a grower. Always follow the label directions and do not cut the rate of the specific herbicide.

Postemergence Weed Control Options in Lentils:

    Sencor: common rate 1/6 to 1/4 lb/ac. Sencor is used for broadleaf weed control and will provide excellent control of wild mustard, field pennycress, shepherdspurse, and lambsquarters. Sencor will provide good control of small wild buckwheat, kochia, and wild sunflower. One post application should be made per season. Crop injury may result if the crop is under stress conditions caused by cold weather. Apply when weeds are small (less than 2 inches in height or diameter) and before the crop is 6 inches tall.

    Assure II: 8 oz/ac for annual grass control; 10 oz/ac for suppression of quackgrass. The addition of 1 gallon of petroleum oil per 100 gallons of water is recommended.

    Poast: 0.5 pint/ac for green foxtail, 3/4 - 1 pint/ac for volunteer grain, wild oat and yellow foxtail, split applications of 1.5 pints/ac followed by 1 pint/ac for suppression of quackgrass. The addition of modified seed oil at 1.5 pints/ac or Dash at 1 pint/ac is recommended to enhance grass control.

    Assure II and Poast should not be tankmixed with Sencor. Reduced grass control can be avoided by applying Assure II or Poast at least 1 day before or 5 days after application of a broadleaf herbicide.

Postemergence Weed Control Options in Field Pea

    Basagran: 1 to 1.5 pints/ac for broadleaf control. Contact herbicide needs 15 to 20 gallons of water per acre. The addition of modified seed oil at 1.5 pints/ac or Dash at 1 pint/ac will improve control. For hard to control broadleaves, such as, kochia or wild buckwheat or for the suppression of Canada Thistle, split applications of 1 pint/ac, seven to ten days apart in needed for consistent control. Apply when peas have reached the 3 leaf stage or 4 nodes (approximately 2 to 4 inches in height). If applying split applications, the second application can be safely applied to taller peas (6 + inches).

    Pursuit: 0.72 oz/ac for broadleaf control, will give suppression of black nightshade.. The addition of non-ionic surfactant at 1 quart per 100 gallons of water will improve control. Pursuit can be applied to peas from the first trifoliate to prior to bloom. Pursuit is an ALS inhibitor and will not control ALS resistant kochia.

    Chiptox (MCPA sodium salt), MCPA (Certain Brands), or Thistrol (MCPB): 0.5 to 1 pint/ac for good control of wild mustard, redroot pigweed, and other broadleaf weeds. Apply to 4 to 6 inch pea vines. Peas might be slightly injured and will usually recover. The potential of injury increases when peas are above 6 inches in height and when temperatures exceed 85 F or when the peas are under heat/drought stress.

    Sencor: common rate 1/6 to 1/4 lb/ac. Sencor is used for broadleaf weeds and will provide excellent control of wild mustard, field pennycress, shepherdspurse, and lambsquarters.. Sencor will provide good control of small wild buckwheat, kochia, and wild sunflower. One post application should be made per season. Crop injury may result if the crop is under stress conditions caused by cold weather. Apply when weeds are small (less than 2 inches in height or diameter) and before the crop is 6 inches tall.

    Assure II: 8 oz/ac for annual grass control; 10 oz/ac for suppression of quackgrass. The addition of 1 gallon of petroleum oil per 100 gallons of water is recommended.

    Poast: 0.5 pint/ac for green foxtail, 3/4 - 1 pint/ac for volunteer grain, wild oat and yellow foxtail, split applications of 1.5 pints/ac followed by 1 pint/ac for suppression of quackgrass. The addition of modified seed oil at 1.5 pints/ac or Dash at 1 pint/ac is recommended to enhance grass control.
    Assure II and Poast should not be tankmixed with any broadleaf herbicide or reduced grass control can occur. Reduced grass control can be avoided by applying Assure II or Poast at least 1 day before or 5 days after application of a broadleaf herbicide.

Kent McKay, Area Agronomist
North Central Research Extension Center, Minot


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