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Management <br />Leafy spurge is difficult [o manage and can <br />recover from almost any control effort. Therefore, a <br />management scheme that combines control <br />methods over four to five years is recommended. <br />Even after that time, monitor infestations for <br />recurrence and adopt a maintenance program. <br />Cultural control. Vigorous grass growth is <br />an important aspect of leafy spurge control. Over- <br />grazing stresses grasses and makes them much less <br />competitive with weeds, leafy spurge in particular. <br />Irrigation, where applicable, may favor grass <br />growth and make ii more competitive with leafy <br />spurge. <br />Figure 1: Number of acres in Colorado <br />infested with leafy spurge, 2002. <br />Chemical control. For optimum leafy <br />spurge control, proper timing of herbicide <br />application is imperative. Research from North <br />Dakota State University indicates that Tordon 22K <br />(picloram) 2,4-D, Banve]Nanquish/Clarity <br />(dicamba) aze most effective when applied in <br />spring when true flowers emerge (not just bracts). Fall application to leafy spurge <br />regrowth also is good timing for these herbicides. <br />Roundup (glyphosate) is most effective when applied sequentially (1.0 <br />quart per acre (A) at one month intervals, coupled with fall grass seeding. Make <br />the first application a[ the beginning of June and a second application one month <br />later. Occasionally, leafy spurge will recover from these Roundup treatments. An <br />application of 2,4-D (2.0 quart/A) in September can control regrowth. Sow <br />perennial grasses in late fall. <br />Tordon is the most effective herbicide for leafy spurge control. Treat <br />large, readily accessible azeas with 1 quart/A for three to four consecutive years. <br />More remote areas may be treated with 2 quarts/A for two consecutive years or <br />once every other year for three yeazs, depending on leafy spurge recovery after <br />[he first [reatment.With either treatment, monitor infestations. Retreat with 1 <br />quart/A of Tordon when shoot control is less than 75 percent. <br />Tordon may be tank-mixed with 2,4-D to provide adequate control. <br />Apply 1 to 1.5 pints of Tordon with 1 to 1.5 quarts/A of 2,4-D in spring when <br />leafy spurge flowers. When this application is made for three to five consecutive <br />yeazs, leafy spurge shoot control is generally 80 to 90 percent and cattle will feed <br />in the azea again. <br />BanveWanquish/Clarity also is effective against leafy spurge. Apply 2 <br />quarts/A in spring for three consecutive years. Often control is not very good in <br />the first yeaz but improves over the next two yeazs. At that time, a maintenance <br />schedule that uses low rates of BanveWanquish/Clazity + 2,4-D (4 to 8 ounces + <br />0.5 to 1 quarVA), or Tordon + 2,4-D (1 pint + 1 quart/A) as needed can be used to <br />keep infestations under control. Note: Avoid using soil-active herbicides such <br />as Tordon or BanveWanquisWClarity near windbreak plants or other <br />desirable woody vegetation. Plant injury or death can occur. Also, do not allow <br />any herbicide to drift onto desirable woody vegetation for [he same reasons. <br />Recently, Plateau (imazapic) was registered to control leafy spurge in <br />noncrop areas. It can be used safely around trees but may temporarily injure cool- <br />season perennial grasses. Apply Plateau at 8 or 12 fl. oz/A in fall, followed by 4 <br />fl. oz/A the following spring at flowering. Add a methylated seed oil a[ 2 pints/A <br />to the spray solution. A liquid nitrogen fertilizer solution may be added to the <br />spray mixture to increase weed control, but it may increase cool-season perennial <br />grass injury. <br />