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ISSUE 4  May 25, 2000



    The 2000 NDSU Weed Tour will be held Thursday, July 6, 2000. Below is the schedule with locations and times.

8:30 - 11:30 - NW-22 Research Farm, Fargo, ND (SW corner of I-29 and County Rd 20)
    Plot booklets will be available along with a guided tour of field research experiments. Researchers will be present to explain the objectives of the experiment, discuss study treatments, and answer questions.

    Experiments include: Wild oat and broadleaf weed control in wheat, weed control in flax, canola, field pea, chick pea, and sunflower, carryover, rotation studies, biennial wormwood control and biology studies, application technology with variable rates, speed, and gallonage, and drift studies.

11:30 - 1:00 - Lunch at Royal Fork Buffet (13th Avenue)
    Lunch is free to all tour attendees and will be paid by NDSU Ext Weed Sci projects.

1:00 - Travel to NDSU Agronomy Seed Farm, Casselton, ND
    Weed control in corn, soybeans, and dry edible beans and adjuvant studies.


1:00 - Travel to North of the Airport (County Rd 20) for tour of sugarbeet weed control plots. Dr. Alan Dexter will lead a tour for those interested in sugarbeet weed control research.



    Please make the following corrections to the 2000 ND Weed Control Guide. We apologize for any inconvenience this may cause.

Page 12 - Delete Paramount. Paramount is only labeled postharvest or prior to planting wheat. Paramount is not labeled in-crop to wheat.

Page 96 - Crop Rotation Restrictions:
Ally and CRP grasses = 4 months after application
Assert and barley = NCS - Next Cropping Season
Assert and sugarbeet = 20 months after application
Assert and wheat = NCS - Next Cropping Season
Curtail/M and flax = NCS - Next Cropping Season
FirstRate and dry bean = 9 months after application
FirstRate and chickpea = 9 months after application
FirstRate and dry pea = 9 months after application
Lightning and sunflower = 18 months after application

Page 105 - Weed ratings for POST applied herbicides:
Harmony GT and wild buckwheat = change rating to E.
Raptor and common ragweed = change rating to P.

    Data from studies printed in the NDSU Weed Control Research books were summarized for wild buckwheat control from thifensulfuron (Harmony 75DF). Across several different environments and rates ranging from 0.12 to 0.5 oz ai/A (labeled rates in wheat are 0.225 to 0.45 oz ai/A) produced an average wild buckwheat rating of 92% control.



    Question: Should I spray my wheat that has been injured by frost?

    Answer: Previous experience in spring wheat indicates spraying AFTER a freeze has little effect on crop safety. Reduced weed control may result if plant tissue was injured by the frost preventing herbicide uptake. Weather after the frost is the most important factor influencing performance. Prolonged low temperatures may reduce already stressed plants ability to metabolize the herbicide. Yellowing may occur with some sulfonylurea herbicides under these conditions. The activity and risk of crop wheat injury increases with some POST grass herbicides (contains fenoxaprop, Achieve) as temperature decreases. If in doubt, delay application for two to three days after the frost so both crop and weeds can recover and resume growth.

    Question: Due to our overly wet conditions in eastern North Dakota I am having a problem with the weed curly dock in my fields. Crops that I need control in are soybeans, edible beans, and corn. If you could help me with this problem I would greatly appreciate it.

    Answer: The following herbicides are registered for control of curly dock.
Soybean and dry bean:
Pursuit, Lexone and Sencor and Roundup on Roundup Ready Beans. Be careful with the rate of Sencor and Lexone because high pH soil greatly enhances the activity which leads to soybean injury. Sencor and Lexone is NOT labeled in dry bean. Read and follow label directions because herbicides may only suppress dock.

Banvel, Celebrity Plus, Clarity, Distinct, and Hornet. Again read and follow label directions to achieve maximum control.

    Question: I heard Hamony GT can be applied on soybeans as well as small grains. Is this true?

    Answer: DuPont has issued a supplemental label for Harmony GT on soybeans in ND, MT, MN
(North of Hwy 28), and SD ( North of Hwy 212).
Rate: 0.083 oz 75DF/A = 1/12 oz 75DF/A
Adjuvants: NIS with or without nitrogen fertilizer
Weeds: Annual smartweeds, lambsquarters, pigweed, velvetleaf, sunflower.
Label allows tankmix with post grass herbicides, Basagran, and Galaxy. The label does not recommend tankmix of Harmony GT with Pursuit. See label for reasons. Other soybean herbicides labels may allow a tankmix with Harmony GT. See individual labels.

    Question: I heard there was a new product called Bronate Pro. What is it?

    Answer: A new label has been issued for Bronate Pro. Bronate Pro is a twin-pack of Puma and Bronate for grass and broadleaf weed control in winter wheat, spring wheat, and durum. The box contains a 1.65 gallon container of Puma (Pro One) and a 2.5 gallon container of Bronate (Pro Two).
Each box will treat 20 acres, which equals Puma at 0.66 pints/A and Bronate at 1.0 pints/A. There will be limited quantities of Bronate Pro available in the 2000 growing season.

Richard Zollinger
NDSU Extension Weed Specialist



    An evaluation of several biotypes of the rigid ryegrass in Australia including that biotype that has gained resistance to glyphosate (Roundup) has allowed farmers more information on the resistant mechanism in weeds. Research revealed that application between the two-leaf and tillering stages of a susceptible biotype of the grass made the weed slightly more susceptible to Roundup application than if the herbicide was applied at other growth stages. Roundup is a nonselective herbicide that has been used without the appearance of any resistant weed biotypes for the past 20 years. The new biotype of rigid ryegrass in a field in Northern Victoria, Australia that has recently shown resistance to Roundup after the chemical was used consistently for 15 years on the location does not show susceptibility at any growth stage. The resistant weed when
tested exhibited nearly 10-fold more resistance than susceptible biotypes of this same grass to Roundup. The resistant weed was also resistant to three different salt formulations of glyphosate. It was also nearly three-fold more resistant to Hoelon (diclofop-methyl), a grass control herbicide with a different mode of activity, but ironically was susceptible to other commonly used selective and broad-spectrum herbicides such as trifluralin (such as Treflan), triasulfuron (Amber), oryzalin (Surflan), norflurazon (such as Zorial), metribuzin (such as Sencor), diuron (Diuron), simazine (Simazine), sethoxydim (Sethoxydim), fluazifop-P (such as one of the Fusilades), glufosinate (Liberty) or paraquat (such as Gramoxone Extra). Shoot and root growth with the resistant rigid ryegrass was observed through many experiments and results so far reveal that the resistance mechanism might be associated more with the shoot than the root through possibly internal metabolism and resistant target-site enzymes as well as foliar uptake and translocation within the plant or even within cells. Consider herbicide rotation and application timing on fields in order to prevent weed resistance from developing.

Denise A. McWilliams
Extension Crop Production Specialist

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