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Campbell: Controlling Yucca & Woody Plants

Stacy Campbell
K-State Research and ExtensionKSU research & extension
May 30, 2013

Controlling Yucca & Woody Plants in Pastures

Yucca plants, which are also called soapweed by many people, have nearly
over ran some rangelands.

Across much of western and central Kansas, several years of drought plus grazing weakened many rangeland plants. A plant that stands out throughout the area, though, is yucca, which has nearly taken over some pastures. While able to produce attractive flowers, dense stands of yucca can devastate grass production.

Yucca plants develop rapidly once established on drier rangeland sites. They produce a deep taproot that competes aggressively for the limited water in these soils. Since cattle rarely eat it during summer, grass production decreases while yucca thrives.

Herbicides like Remedy Ultra, PastureGard HL, Pathfinder II, and Velpar L or Pronone Power Pellet Herbicides are all labeled in Kansas for control of yucca. General spraying of whole pastures for any type of weed control is cost prohibitive, although small patches or larger areas of yucca can and should be controlled before they expand.

In the past Velpar L or Pronone Power Pellet Herbicide which has the same active ingredient as Velpar L (Hexazinone) probably were used the most for individual soil applied treatment of yucca plants with pretty good results. Velpar L is in a liquid form and has to be applied with an exact delivery hand-gun applicator, 4 ml of product/inch of stem diameter which was a hassle, or the more convenient Pronone Pellets. Using either of these products you could expect to see some grass damage where the product was applied around the plants.

In the past few years some other herbicides Remedy Ultra, Pathfinder II and PastureGard HL have been applied as a growing point and leaf base (crown) treatment with better results on yucca at the same price or maybe even less than Velpar L or the power pellets. Pathfinder II is the same product as Remedy Ultra it is a ready-to-use product and therefore will probably be more expensive than Remedy Ultra. In yucca control trials conducted by K-State Research & Extension results of a spray solution of 2% Remedy Ultra or 1% PastureGard HL in diesel fuel has resulted in roughly 80% or greater control, with less damage to the surrounding grass since the product is sprayed in the center of the plant. Any of these products should be applied from April through June when the plants are actively growing.

If you are going to spray many yucca plants throughout a pasture a spray dye would help you to know which plants you have sprayed.

These same products Remedy Ultra , PastureGard HL and Pathfinder II can also be used as a basal bark application on controlling many woody plants including Osage orange (hedge), and locust trees. Basal bark application is simply thoroughly spraying the entire basal parts of brush generally to a height of 15 to 20 inches. Some products may have a limitation of 6-inch basal diameter for effectiveness. With this method there is a wide window of application Pathfinder II and PastureGard HL can be applied any time, except when snow or water prevent spraying to the ground line.

Most woody plants are susceptible to properly applied herbicides. Herbicides effectiveness depends upon using the proper chemical at the correct time and rate. Each species has a period when it is most susceptible. Environment factors such as precipitation, temperature, and wind also affect herbicide activity. For herbicide control of woody plant species there are basically five application methods foliar, dormant stem, soil applied, basal bark and cut stump or frill application.

Which method to use depends on the plant species, size of invasion, topography, economics, adjacent land use, and management objectives. Combinations of methods often are less costly and more effective than a single method, particularly with mixed brush species. Prescribed burning followed by herbicide applications on the re-growth improves control of persistent species. Because successful brush control normally requires follow-up treatments, applying herbicides to prevent sprouting is more efficient than repeatedly killing re-growth. As always read and follow the label directions and if you want more information on controlling yucca or woody species in rangeland contact your local County Extension Office or go to www.oznet.ksu.edu

KSK CHRISTMAS
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