Note: In addition to the document below, further information pertaining to brush management can be found at :Brush Management spec 314

CONTROL OF UNDESIRABLE PLANTS

Mark Moseley, Phillip Sims and Dan Persons

Sand sagebrush - 1/2 to 1 lb 2,4-D LV ester in 1 gal. diesel fuel with water to spray 4 gal. of solution per acre. Apply in Spring, generally mid-May to mid-June, when plants are in 3/4 to full foliage and actively growing. To increase spectrum of control add 1/8 to 1/4 lb of dicamba to mix.

Eastern red cedar - for trees less than 10 ft. spot treat with Velpar or Picloram. Apply prior to or in rainy season, April-May or September to October. Apply Velpar (hexazinone) 2-4 mg/inch of stem diameter at breast height within 3 ft. of root collar. Apply Grazon PC (picloram) in same manner at 3-4 ml/ft of plant height.

Prickly pear cactus - Use 1 to 2 pints of Grazon PC per acre in mid-April through May or in late-August to early November. If burned, apply 1 pint per acre, about 30 days after burning.

Sand shinnery Oak- Apply 1/2 lb a.e. (1 pint) of triclopyr (Grazon ET, 4 lb/gal.) when leaves are 1/2 to fully developed, usually June, when moisture conditions promote active growth. Spray mixture includes 1 pint of triclopyr added to 2-8 pints of diesel fuel, an approved emulsifier and sufficient water to make 3-4 gal. per acre of total mix. The oil to water ratio should be 1:5.

Spike 20P (tebuthiron) can also be used at 5-15 lb product. Results depends on past treatment and soil condition.

Salt cedar - Repeat spraying with 2,4-D at about 1/4 to 1/2 lb/acre to defoliate plants several times each growing season. Recent work by NMSU scientists found Arsenal + Roundup at .25% V/V each to be effective with a carpet roller application.   (Note: Arsenal+Roundup is not currently labeled in Oklahoma.)

Mesquite - June application, 40 to 90 days after green growth appears when soil moisture and temperature (75 F at 12 inches) is adequate of triclopyr (Remedy) at 1 pint/acre or cloropyrolid (Reclaim) at 0.66 to 1.33 pint/acre. Reclaim may be used in September according to Dow-Elanco supplemental label.

Yucca - Apply Velpar at 2 cc/plant on uphill side (see below for details of recent studies).

Annual and perennial broadleaf weeds - Use .5 to 1 lb of 2,4-D amine or low volatile ester when weeds are in early growth stages and actively growing. Banvel or Grazon PC can be added to broaden the spectrum of action. Follow label instructions.

Mist blower applications - The following hormone type herbicides (2,4-D, 2,4-DB, MCPA, MCPP, MCPB, dicamba, picloram, cloropyrolid, and triclopyr) may no longer be applied with a mist blower except on rangeland, pasture, and crop areas where control of undesirable vegetation with a hormone type herbicide is necessary and a specific type of terrain feature such as a gully precludes the use of any other type of ground application equipment. Application of a hormone type herbicide under this exception is subject to the following restrictions:

1. At no time during the application will the outlet be allowed to be pointed above horizontal.

2. At no time will an application be performed in - wind speed of over 10 MPH.

3. The person making the application shall keep those records as required by Section 3-83 (Keeping of Records), Oklahoma Pesticide Applicators Law.

Note:The use of company names in this publication does not imply endorsement by the USDA-ARS, or the product names or criticism of similar ones not mentioned.

YUCCA CONTROL

Control of undesirable species is always of some concern in this region of the Southern Plains. Species that may be a problem include sand sagebrush, shinnery oak, salt cedar, yucca, Eastern red cedar, prickly pear cactus, mesquite, and annual weeds and grasses. Most of our recent work has centered on yucca control since there are no current recommended control measures.

Yucca. Individual treatment of yucca plants have been obtained with Hyvar XL and Velpar at 7.5 ml a.i./plant and Grazon 1OK and Graslan 20P at 5 g a.i. per plant (Table 1). Banvel 1OG, Escort RP and Grazon PC did not provide sustained control of yucca. Even with the more effective herbicides there were some resprouts of yucca in the second growing season.

Table1. Herbicide screening for Yucca Control

Another study (Table 2) was conducted in 1991 with the most promising herbicides to determine the minimal rates necessary for yucca control while reducing grass damage and costs. All three herbicides, even at the lowest rates, showed good control of yucca one year after treatment. Even with these lower rates, however, there was still some soil sterilization and damage to the surrounding grasses. Generally Graslan 20P, Hyvar XL and Velpar caused dead spots of about 30" diameter. Grass recovery had began by the second growing season following treatment for all treatments except the heavy rate of Graslan 20P.

A current study with Hyvar XL, Velpar and Graslan 20P is under way with even lighter rates being tested. Rates being tested range from .07 to .6 g a.i./plant with cost ranging from $0.004 to about $0.06/plant.

Table 2 Percent control of Yucca with lighter rates of herbicides.