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Locations <br />There are also several locations which may create special problems which the <br />Division would like to address. The main one is topsoil. As previously mentioned, <br />topsoil, both prior to stripping/stockpiling and prior to redistribution, is an area that <br />should receive top priority for noxious weed control. However, the use of some <br />herbicides on topsoil may create a problem due to their residual effects. For <br />instance, if one of these herbicides is applied to a topsoil stockpile at rates lethal to <br />various weeds and the topsoil is redistributed before the herbicide has broken down, <br />problems may arise with germination and establishment of desirable vegetation after <br />seeding this soil. The same problem might arise if a soil is treated prior to <br />stockpiling. If the treated soil is near the surface of the stockpile it may inhibit the <br />germination and establishment of a stabilizing non-noxious cover on the pile. <br />Another problem can arise due to the mobility of some herbicides through soil. If a <br />mobile soil residual herbicide is used over an entire topsoil pile the entire pile may <br />become contaminated. If this soil is then redistributed over a set area, before the <br />herbicide has broken down, this entire area may exhibit problems involving <br />germination and establishment. To prevent these potential problems it is suggested <br />that both residual and mobile residual herbicides not be used on topsoil for a <br />minimum of six months prior to stripping/stockpilingand 12 months prior to <br />redistributing from a stockpile. If noxious weeds are present and require treatment <br />within 18 months of these operations anon-soil active, non-residual herbicide such <br />as glyphosate should be employed. This treatment would allow reseeding to occur <br />immediately. <br />Another area of concern is the use of herbicides around desirable vegetation (for <br />instance trees and shrubs). Precautions should always be taken to prevent damage to <br />non-target species and product labels should be read thoroughly before applying any <br />herbicide. Desirable broadleaf vegetation is usually very sensitive to most <br />herbicides and the slightest amount of herbicidal drift on the leaves or leaching of a <br />herbicide into the root system may cause significant damage. <br />One final area that requires special consideration is that of aquatic environments, <br />both surface and groundwater. Several products are specifically labeled for use <br />around water. Other products should never be used around water. Once again, <br />always read the label and follow the recommendations carefully. It is against the <br />law to use any product off label. Your local extension agent or Weed District <br />personnel should be able to help choose the proper product for the intended job and <br />advise against misuse. <br />Part VII of this document has provided insight into control of a few of the more <br />serious weeds in Colorado and precautions to be taken with respect to various sites. <br />Specific herbicide recommendations have not been included so as to not promote <br />any specific products. Also, the Division would prefer that the local agricultural <br />-13- <br />