ISSUE 6 June 9, 2005
UNUSUAL WEEDS YOU MIGHT NOTICE
A dominance of three plant species are being sent for identification.
Swamp ragwort - a plant looking similar to a sowthistle, having large hollow, hairy stem with small yellow flowers. The plants proliferate where there where wet areas and drown-out areas in fields. Pictures of this plant are not in may ID books. Pictures and descriptions can be found in W-1103 North Dakota Noxious and Troublesome Weeds Pocket Book available from the NDSU Extension Distribution Center. Pictures and plant description can also be found at the Griggs County Extension Service website:
Swamp smartweed - is another plant you might find in wet areas of the field. Pictures can be found in most weed ID books.
Dame’s rocket - a mustard plant that usually thrives on roadsides, ditches, and near shelterbelts and tree plantings. It has a distinctive purple flower. Pictures can also be found in W-1103 North Dakota Noxious and Troublesome Weeds Pocket Book.
CONTROLLING ROUNDUP READY VOLUNTEERS IN ROUNDUP READY CROPS
Which are the most effective herbicides and at what rates are question asked how to control different Roundup Ready crop volunteers in Roundup Ready crops. Refer to page 126 of the 2005 ND Weed Control Guide for a table that contain control information. This is the first addition of new material in the weed guide for several years. The ratings are from a compilation of research conducted by NDSU Weed Scientists at Fargo, Carrington, and Minot.
LATE HERBICIDE APPLICATIONS IN SMALL GRAINS
Rains have caused a delay in some herbicide applications in small grains and increased the demand for aerial applications. The cool weather has facilitated tillering in small grains but now plants from early seedings are beginning to joint. Many herbicides can be applied during tillering and others after jointing begins. See page 12 of the 2005 weed guide for a quick summary of those products that can be applied after small grains begins jointing. Those that cannot be applied after jointing begins are Aim, Assert, Dakota, dicamba, Everest, Maverick, Olympus, Puma (barley only), and Silverado. Follow label for the correct application window for herbicide application.
GRAZING/HAYING RESTRICTION FOR RAPTOR ON FIELD PEA
The 2005 ND Weed Guide incorrectly list the haying/grazing restriction for Raptor on field pea as 120 days after application. The correct restriction is 0 days for Raptor on field pea and all other crops. Field pea can be hayed or grazed immediately after application.
POST HERBICIDES ON STRESSED CORN AND SMALL GRAINS
Wheat is a cool-season grass and is adapted to cool conditions. The likelihood of small grains being stressed from the environment is low except those plants affected by standing water. Small grains should tolerate POST herbicides well as long as label directions are followed with respect to proper application timing, allowed tank-mixes, and appropriate adjuvants.
Corn is warm-season grass and strives in hot weather especially with good soil moisture. The cooler conditions have probably caused much of the corn to appear yellow and stunted. The best solution is warmer temperatures.
Many are asking about the impact of POST herbicides on corn stressed by environment. Cold or cool temperatures slow corn metabolism increasing the risk of injury from herbicides. Section A4 on page 67-68 of the 2005 ND Weed Control Guide describes general temperature effects on weed control and crop tolerance of several herbicides. Normally, growers would wait to apply herbicides until soil dries and plants resume normal growth. However, weeds are also growing vigorously and large weeds are more difficult to control and require full label rates for adequate control.
Several POST herbicide labeled in corn are generally very safe, such as, atrazine, bromoynil, Basagran, Starane, Hornet, Stinger, WideMatch, Callisto, Accent, and Option. Option contains a safener (isoxadifen) which impart excellent safety. Roundup Ready corn, Liberty Link, and Clearfield corn have excellent safety to prescribed herbicides allowed for use. Avoid using 2,4-D or Curtail on corn, if at all possible, to avoid injury. If so, follow the label with exactness.
Penultimately, follow all label directions with regard to application. All herbicides have directions for use to maintain crop safety. Another practice to assure greater corn tolerance is to avoid spraying at the upper limit of the crop stage. For example, do not spray Basis to corn beyond the 6 inch stage, dicamba beyond the 8 inch stage, Distinct from corn emergence to 4 inches tall, Accent past the 20 inch tall stage of corn, or Steadfast past the 12 inch stage of corn. Use the most restrictive application window when tank-mixing two or more herbicides together. Adjuvants can make a difference also. MSO type adjuvants do not cause herbicide phytotoxicity in cool weather but rather in very humid and hot weather. MSO type adjuvants usually give greater herbicide enhancement than nonionic surfactants and petroleum oil (COC) adjuvants. Basic Blend adjuvants are non-oil type adjuvants that perform similar to MSO type adjuvants.
HERBICIDE UPDATE - PART 1
Mode of action: ALS inhibitor (1)
a.i.: thifensufuron + tribenuron
Crops: Small grains
Comments: The label for DuPont's new "Affinity TankMix" herbicide for wheat and barley has been approved by the EPA. Affinity is a 50% soluble granule formulation, available in 48 oz jugs and via the Precision Pak bulk machines. With a rate range of 0.6 oz to 1.0 oz/A , one 48 oz container will treat 80 acres at the 0.6 oz rate. Affinity 50%SG (4:1 ratio of thifensulfuron:tribenuron) is similar to Harmony Extra 75%XP (2:1 ratio of thifensulfuron:tribenuron). Harmony Extra will be sold in higher value and speciality markets. Affinity is a new formulation containing TotalSol soluble granules or SG formulation as opposed to the XP formulation of many other Dupont products. SG formulation makes more product soluble in the spray tank and facilitates easier and more effective sprayer cleanout.
Harmony GT XP (Dupont)
Mode of action: ALS inhibitor (1)
Crops: Clearfield canola (imazethapyr tolerant canola with the Smart trait)
Comments: Supplemental labeling has been approved allowing Harmony GT to used on imazethapyr tolerant canola possessing the Smart trait. Apply at 0.4 oz/A with an approved NIS to canola in the 3 to 6-lf stage. Can be tank-mixed with Assure. Allow a 65 day PHI. Follow all guidelines and restrictions on the label.
Mode of action: ALS inhibitor (1)
Comments: ND Dept of Ag has issued a 24(c) Supplemental Label allowing aerial application. Apply Option at 1.5 oz/A + MSO at 1.5 pt/A + UAN 1.5-2 qt/A or AMS 1.5-3 lb/A. Aerial application should be made in a minimum of 5 gallons of water per acre.
NDSU Extension Weed Specialist