How Can I Control Poison Oak?

Do you want to control poison oak chemically?

Do you want to control poison oak with stump applications?

Do you want to control poison oak with basal bark applications?

Do you want to control poison oak mechanically?

Stump treatments are most effective during periods of active growth. Cut poison oak stems 1 to 2 inches above the soil surface, and immediately after cutting, treat the stump. A delay in treatment will result in poor control. Apply an herbicide such as glyphosate, triclopyr, or combinations of triclopyr with 2,4-D with a paintbrush that is 1 to 2 inches wide or with a plastic squeeze bottle that has a spout cap. Treatment solutions should contain either undiluted glyphosate, triclopyr amine, or a 20 to 30% triclopyr ester solution mixed with 70 to 80% methylated or ethylated seed oil.

Basal bark applications can be made almost any time of the year, even after leaves have discolored or dropped. Apply triclopyr to basal regions of poison oak using a backpack sprayer with a solid cone, flat fan, or a straight-stream spray nozzle. Thoroughly cover a 6- to 12-inch basal section of the stem, but not to the point of runoff.

The effectiveness of herbicides applied to poison oak foliage depends upon the plant’s growth stage and whether spray-to-wet coverage and proper concentration occurred. Foliar application is most effective after leaves are fully developed and when the plant is actively growing. This period is normally from April into June or July, when soil moisture is still adequate. The flowering stage is the optimum time to spray. Do not apply herbicides before plants begin their spring growth or after the leaves have begun to turn yellow or red in late summer or fall.

You can physically remove plants located in a yard or near houses through hand pulling or mechanical grubbing using a shovel or pick. It is essential to remove the entire plant including its roots. Remove plants in early spring or late fall when the soil is moist and it is easier to dislodge rootstocks. Grubbing when the soil is dry and hard usually will break off the stems, leaving the rootstocks to vigorously resprout. Detached and dried brush still can cause dermatitis, so bury or stack the plant material in an out-of-the-way location, or take it to a disposal site. Do not burn poison oak.

Poison oak is a native species in the western United States. As such, several indigenous insects and pathogens already are present. Typically, biocontrol isn’t an option with a native species. Furthermore, in most areas, poison oak is not a pest, but rather a natural component of the plant community. Don’t burn poison oak, since it creates a serious health hazard and doesn’t effectively reduce infestations. Grazing by sheep and goats can be effective in small areas. Deer or horses also will graze poison oak when the foliage is young, before the plant flowers.