Poison Oak

Asked May 20, 2015, 10:09 AM EDT

Hello, I have a small hobby farm with grazing sheep and horses that has poison oak everywhere! I am highly allergic to poison oak and I get it transferred to my by my animals. I know that it will be almost impossible to eradicate it completely, but I would like to know what herbicide that you would recommend for this situation. I need an herbicide that will kill poison oak and not hurt my livestock, if they should happen to eat some. I also have a problem with milk thistle and hemlock...will the same herbicide work on that? Thank you very much for your time! Amy

Marion County Oregon pesticide safety livestock horticulture

1 Response

Here are two herbicides that can be used in pasture areas but follow grazing restrictions on the label. Both are effective on poison oak but glyphosate will kill grasses.

Glyphosate is also effective on thistle and poison hemlock. Crossbow will also work but not as well as other broadleaf herbicides.

Make sure animals cannot graze the area with poison hemlock after spraying until all evidence of the plant is gone. It is still toxic and livestock are more prone to eat it after treatment is applied.

glyphosate

Rate 3 to 3.75 lb ae/A broadcast or apply as a 2% solution with hand-held equipment.

Time Apply when plants are actively growing at or beyond early to full bloom stage. Results are best if applied after fruit forms. Make late summer or fall treatments before leaves lose their green color. Use higher rates for plants that have reached woody stage of growth.

Remarks Treat foliage when plants are growing rapidly. In orchards, prevent spray mist from contacting foliage, green bark, suckers, or fruit of crop trees or other desirable vegetation. If spray contacts immature bark on main trunk, serious localized or translocated damage can result. Roundup is a nonresidual herbicide requiring subsequent seedling control.

Caution Controls grasses and other vegetation in treated area.

Site of action Group 9: inhibits EPSP synthase

Chemical family None generally accepted

triclopyr ester (Garlon 4) or triclopyr amine (Garlon 3A) or triclopyr + 2,4-D ester (Crossbow)

Rate Spot treat: use 3 lb ae Garlon 4 or 2.25 lb ae Garlon 3A with 100 gal water; or 1 pint Crossbow in 12 gal water. Broadcast: use 4 to 8 lb ae/A Garlon 4, or 6 to 9 lb ae/A Garlon 3A, or 1 to 2 quarts/A of Crossbow.

Time Apply when plants are actively growing.

Remarks Foliage must be thoroughly wet.

Caution Garlon products are registered for use on rights-of-way, industrial sites, and forestry (release and site preparation). Crossbow can be used on permanent pastures and rangeland up to 1.5 lb ae/A. Observe all grazing and harvesting restrictions.

Site of action (all) Group 4: synthetic auxin

Chemical family (triclopyr) pyridine; (2,4-D) phenoxy acetic acid

e are two herbicides that can be used in pasture areas but follow grazing restrictions on the label. Both are effective on poison oak but glyphosate will kill grasses.