ISSUE 8 JUNE 24, 1999
LIMITS ON LATE FOXTAIL HERBICIDE APPLICATION IN WHEAT
Wheat is rapidly growing and as well as weeds including green and yellow foxtail (pigeongrass). If herbicide application is still required for foxtail control in wheat, consider the following wheat and foxtail stage limits for post-emergence foxtail herbicides:
Up to boot
Up to 4-leaf
Up to 6-leaf
Refer to herbicide labels and NDSU Extension Service circular W-253 '1999 North Dakota Weed Control Guide for required information on herbicide use.
PARAMOUNT RECEIVED LIMITED LABEL FOR LEAFY SPURGE
A new herbicide has joined the battle against leafy spurge. Paramount has been labeled for leafy spurge control along roadsides, fence lines, rights-of-way and non-crop areas in North Dakota. The maximum use rate will be 8 ounces of product peracre (6 oz ai). Paramount will have use restrictions similar to Plateau, that is you cannot hay or graze areas where Paramount has been applied.
Research with quinclorac (the active ingredient in Paramount) has been conducted at NDSU since 1993, so use rates, timing, and species controlled are well known with this new herbicide. Research has shown that quinclorac will control leafy spurge and the best long-term leafy spurge control was achieved when quinclorac was applied with a methylated seed oil. Leafy spurge control 12 MAT (months after treatment) averaged 38 and 77% when quinclorac was applied at 0.5 and 1.5 lb/A, respectively, in North Dakota. Leafy spurge control varied by location in a 3 year regional study involving six states, but quinclorac always provided similar to better control than the standard picloram-plus-2,4-D treatment. The current labeled use rate is less than the optimum use rate found in the NDSU trials. However, even at the reduced rate quinclorac will provide good leafy spurge control with minimal to no injury to desirable species. It is likely that once Paramount receives a full registration the use rate will also be increased.
Other studies at NDSU have found that leafy spurge control 12 MAT tended to increase when quinclorac was applied at 1 lb/A or more. Control was increased incrementally from 0.5 to 1 lb/A when quinclorac was applied with the methylated-seed-oil adjuvant Scoil compared to quinclorac alone. Quinclorac applied with Scoil and 28% nitrogen resulted in similar leafy spurge control to quinclorac plus Scoil applied alone.
Quinclorac has several advantages over the presently used herbicides for leafy spurge control. No desirable forage grasses were injured at any quinclorac rate or location in the six-state regional study. Also, the researchers noted that quinclorac did not injure many desirable broadleaf species including lead plant (Amorpha canescens Pursh), purple prairie clover (Dalea purpurea Vent.), prairie wild rose (Rosa arkansana Porter), willow (Salix spp.), and wild raspberry (Rubus spp.). Currently quinclorac is being evaluated to control leafy spurge on the Sheyenne National Grasslands of North Dakota while sustaining the western prairie fringed orchid (Platanthera praeclara Sheviak & Bowles), which is classified as a threatened biological species. Ideally, quinclorac will control leafy spurge, allow the orchid to establish, and have minimum effect on other native species.
Another advantage of quinclorac for leafy spurge control is that the application window for fall treatment is broad. Quinclorac provided similar leafy spurge control when applied from September 1 to October 15 and averaged 74% 12 MAT. Although Paramount can be applied for leafy spurge control in the spring, it is more effective as a fall treatment, especially at the lower use rate imposed.
Paramount is also labeled for field bindweed control, again at 8 oz/A of product. Research at NDSU and other western Universities has found that quinclorac provides excellent field bindweed control and has been termed by some as the best herbicide available for field bindweed. Field bindweed was eradicated in several studies; however, the use rate in these studies was above the current maximum use rate. Paramount is also labeled for Canada thistle and sowthistle "suppression". However, research at NDSU has found this compound provides poor if any thistle control without the addition of other herbicides.
In order to use Paramount for leafy spurge control, the user must have the supplemental label in hand. In addition to the no grazing or haying restrictions, Paramount cannot be applied to water or in areas that channel water to cropland.
NDSU Invasive Weed Control Research
LABELED LIMITS FOR POST APPLICATIONS ON SOYBEANS
The following label limits are approved for post applications in soybeans. Remember to carefully consider the weather and crop conditions before making a herbicide application.
Basagran is restrictive only on weed size in soybeans.
Blazer can be applied to soybeans with 1 to 2 trifoliates.
Blazer + Basagran can be sprayed on soybeans with 1 to 2 trifoliates.
Cobra can be used on soybeans with 1 to 2 trifoliates.
Stellar applications do not apply within 60 days prior to harvest.
Flexstar is restrictive only on weed size and geography.
Pinnacle apply after the first full trifoliate and until 60 days prior to harvest.
Pinnacle + Cobra can be applied on soybeans with 1 to 2 trifoliates.
Pursuit spraying can begin after the first trifoliate, prior to flowering.
Pursuit + Basagran use after the first trifoliate, prior to flowering.
Pursuit + Pinnacle use after the first trifoliate, prior to flowering.
Pursuit + Cobra apply after the first trifoliate, prior to flowering.
Raptor use after the first trifoliate, prior to flowering.
FirstRate apply prior to when soybean is at the 50% flowering stage.
Assure II can be used up to pod set.
Fusilade DX can be applied prior to flowering.
Fusion use prior to flowering.
Poast is restrictive only on weed size.
Select is restrictive only on weed size.
Reflex is restrictive only on weed size and geography.
Rezult do not apply to stressed plants or within 75 days of harvest.
Denise A. McWilliams
Extension Crop Production Specialist
CRISIS EXEMPTION DECLARED ON POAST HERBICIDE
North Dakota has declared a crisis exemption for Poast on buckwheat to control foxtail and other grasses. A specific exemption will not be applied for. The use dates are from June 18, 1999 to July 18, 1999. All federal label restrictions apply. Additional restrictions are a 60 preharvest interval.
A Section 18 exemption for Poast under similar conditions was issued in 1995. The crisis exemption allows up to two applications at a rate of 0.5 to 1.5 pt/A. The product must be mixed in 5-20 gallons of water for ground application and 5-10 gallons for aerial application. Applicators must follow all instructions, warnings and precautions on the product label. The exemption expires July 18, 1999.
EPA APPROVES USE ON GLYPHOSATE-TOLERANT SOYBEANS
The EPA has approved use of Touchdown 5 on glyphosate-tolerant soybeans, including Roundup Ready soybeans and as a harvest aid on all soybeans. Application methods for glyphosate-tolerant soybeans include before, during, or after planting; postemergence; and preharvest. The maximum use rate is 12.8 pints/acre with no more than 3.2 pints/acre applied postemergence up to and including the full bloom stage of soybeans. Pre-harvest applications can be made at a maximum of 1.6 pints/acre with a 7 day pre-harvest interval. Forage and hay of glyphosate-tolerant soybeans can not be grazed or harvested. Approved tank mix partners for postemergence use include Basagran, Flexstar, Fusilade, Fusion, Pinnacle, Pursuit, and Reflex.
The maximum use rate for preharvest use in soybean is 12.8 pints/acre. Preharvest applications can be made at a maximum of 1.6 pints/acre with a 7 day pre-harvest interval. Hay can not be grazed or harvested following a harvest-aid application. All other directions for use and general use precautions for soybeans remain the same as printed in the Directions for Use booklet.
Ammonium sulfate may be added to improve weed control at a rate of 1 to 2% as dry ammonium sulfate (8.5 to 17 lb/ er 100 gallons of water); or at an equivalent rate as liquid formulations for all uses on all soybeans.
ADDENDUM TO CROP PROD ARTICLE IN LAST WEEKS PEST REPORT
In last weeks Pest Report it was suggested that another source of fertilizer could be substituted for Crop Prod for use with some herbicides. Some small grain herbicides (Dakota, Tiller, Cheyenne, Puma, others) restrict the use of fertilizer and other additives so addition of Crop Prod, fertilizer, or any other additives are restricted from use and are against label directions. Read and follow label directions.
NORTH DAKOTA WEED CONTROL GUIDE ON WEB
The 1999 North Dakota Weed Control Guide can be found on the web at:
Not all links are connected at this point but will be modified as time goes on. Up-to-date label changes will be made on the web version that are not contained in the printed version. If any one has any ideas or comments to make the guide better or more complete, please let me know.
NDSU Extension Weed Specialist