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• 1. [Article] Integrating restoration and ecologically based weed management practices for invasive knotweed control

  Japanese knotweed is an invasive perennial shrub that dominates riparian ecosystems. Effective management techniques are currently limited to repeated annual herbicide applications and there is little ...

  Citation × Citation Citation Abstract Copy Title: Integrating restoration and ecologically based weed management practices for invasive knotweed control Author: Rudenko, Melody Japanese knotweed is an invasive perennial shrub that dominates riparian ecosystems. Effective management techniques are currently limited to repeated annual herbicide applications and there is little science-based information about which control tactics result in the greatest management success. Restoration of invaded sites to a functioning riparian plant community is needed to prevent re-infestation of Japanese knotweed or other invasive weed species. Field and greenhouse experiments were initiated in fall of 2007 to generate this information on Japanese knotweed management. A greenhouse experiment was conducted to evaluate the efficacy of the experimental herbicide aminocyclopyrachlor methyl ester for Japanese knotweed control. Treated plants were unable to produce new shoots from underground rhizomes indicating that aminocyclopyrachlor is an effective control. This level of Japanese knotweed suppression is comparable to imazapyr and surpasses the level of control that glyphosate provided under greenhouse conditions. A field experiment was initiated in the Nehalem River watershed in western Oregon to evaluate the integration of chemical weed management with restoration of the site to a diverse native grass plant community. We documented that native grasses could be established at this site, but the long-term survival of these grasses was poor. This result indicates that methods for simultaneous chemical control of invasive knotweed and restoration of sites need to be investigated further. The most effective chemical treatment in terms of visual injury and reduced Japanese knotweed biomass and cost of application was glyphosate applied at a rate of 4.21 kg ae/ha for a cost of $160/ha. A secondary experiment evaluating herbicide tank mixtures of glyphosate with imazapyr, imazapyr with aminopyralid, and triclopyr with 2,4-D was conducted at the same site. The most effective chemical treatment in terms of Japanese knotweed control and cost of application for the tank mixture experiment was imazapyr with aminopyralid applied at rates of 1.12 kg ae/ha (imazapyr) and 0.12 kg ae/ha (aminopyralid) for a cost of $346/ha. Title: Integrating restoration and ecologically based weed management practices for invasive knotweed control Author: Rudenko, Melody Japanese knotweed is an invasive perennial shrub that dominates riparian ecosystems. Effective management techniques are currently limited to repeated annual herbicide applications and there is little science-based information about which control tactics result in the greatest management success. Restoration of invaded sites to a functioning riparian plant community is needed to prevent re-infestation of Japanese knotweed or other invasive weed species. Field and greenhouse experiments were initiated in fall of 2007 to generate this information on Japanese knotweed management. A greenhouse experiment was conducted to evaluate the efficacy of the experimental herbicide aminocyclopyrachlor methyl ester for Japanese knotweed control. Treated plants were unable to produce new shoots from underground rhizomes indicating that aminocyclopyrachlor is an effective control. This level of Japanese knotweed suppression is comparable to imazapyr and surpasses the level of control that glyphosate provided under greenhouse conditions. A field experiment was initiated in the Nehalem River watershed in western Oregon to evaluate the integration of chemical weed management with restoration of the site to a diverse native grass plant community. We documented that native grasses could be established at this site, but the long-term survival of these grasses was poor. This result indicates that methods for simultaneous chemical control of invasive knotweed and restoration of sites need to be investigated further. The most effective chemical treatment in terms of visual injury and reduced Japanese knotweed biomass and cost of application was glyphosate applied at a rate of 4.21 kg ae/ha for a cost of $160/ha. A secondary experiment evaluating herbicide tank mixtures of glyphosate with imazapyr, imazapyr with aminopyralid, and triclopyr with 2,4-D was conducted at the same site. The most effective chemical treatment in terms of Japanese knotweed control and cost of application for the tank mixture experiment was imazapyr with aminopyralid applied at rates of 1.12 kg ae/ha (imazapyr) and 0.12 kg ae/ha (aminopyralid) for a cost of $346/ha. Close