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Poison Hemlock Treatment

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I am looking for best management practices for Poison hemlock. Searching the web, I have found the following options. If anyone has experience controlling Poison hemlock, I would greatly appreciate your feedback on any of the following methods.

• Triclopyr (Ortho Max Poison Ivy and Tough Brush Killer): most effective when applied from seedling to rosette stage

• 2,4-D plus dicamba (1 kg + 0.5 kg ai/Ac)  before plants begin to bud   OR    2,4-D (Agri star): most effective when applied soon after plants reach rosette stage

• Glyphosate (Round-Up): apply to actively growing plants before bolting

• For large infestations, a combination of mowing and then treating the regrowth may be the best option. Follow-up as necessary.

• Continuously monitor for new plants, especially following any disturbance to the soil such as tilling or construction, until the seed bank has been depleted.

• Metsulfuron (Escort) + a nonionic surfactant or silicone surfactant is effective in spring when plants are actively growing. See PNW Handbook for more detail.


Thank you,


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I have put together the following management practices for a RFP we will be bidding out in 2021. If possible, I would greatly appreciate any feedback on the following suggested techniques. 


Poison Hemlock

For Poison hemlock, Contractor must perform foliar applications during the rosette stage of the plant in early spring, typically during the month of May. Chemical suggested for use may include an aquatic approved glyphosate at 2% or triclopyr at 1.5% depending on proximity to the water body. Anticipated active ingredients, percent solution, and timing of applications must be included in the proposal and approved by the LSC CISMA.


Non-Priority Invasives: Reed canary grass, Yellow clover, Bull thistle, Canada thistle, and Garlic Mustard

For non-priority treatments, Contractor will use the following for each species:

Reed canary grass – 2% solution of an aquatic approved glyphosate or triclopyr depending on proximity to the water body.  Foliar applications must be performed during late March – April or in November.

Yellow clover- Mechanical hand pull techniques should be implemented between July – August and must include tamping the ground after each removal. Removed biomass must be bagged, mobilized off-site, and disposed of properly.

Bull & Canada thistle -  2% aquatic approved glyphosate. Bloody glove / hand wiping applications must take place during July – August.

Garlic mustard – Rosettes should be torched in January – March and followed up with hand pull removal in May – June. Mechanical hand pull techniques must include tamping the ground after each removal and removed biomass must be bagged, mobilized off-site, and disposed of properly.



Thank you,


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