Poison oak is a nuisance, and getting rid of it is an even bigger one.
The window for eliminating it through chemical herbicidal spray is almost over, according to Dave Muffoleto, who has had 13 years eradicating it with Foothill Sierra Pest Control.
When using a spray to get rid of poison oak, timing is the crucial element, he said. You don’t want to spray too early or too late.
The best time, he said, is from June to the beginning of August.
Once the plants go dormant, sprays aren’t really effective, he said.
People can hire help to spray or do it themselves, if they take the proper precautions when using chemicals, said Jack Bennett, of Sonora, a longtime Master Gardener. Bennett has years of experience with poison oak on his 60-plus acres in Calaveras County.
There’s organic options to chemical sprays for those who prefer to not use herbicides.
People who are going to try to spray on their own need to cover the plant 100 percent, and if it’s growing up something like a tree, the stalks should be notched and then the solution brushed onto the stems, Muffoleto said.
People should wear long sleeves and pants and gloves when doing poison oak control. Muffoleto recommends buying a cheap painter’s suit and covering any exposed skin with olive or vegetable oil to block the skin pores and protect against getting poison oak oil on the skin.
The oil makes it a “little less penetrable,” he said.
People who are really sensitive should wear a mask and goggles.
Trying to only control poison oak through weed eating or bulldozing won’t do you any good, Bennett said.
However, if you apply a chemical or herbicide treatment and let the plant die, then cut it all down, it should be taken to either a slash yard or put on a remote part of your property where nobody will touch the leaves.
The oil on the leaves that causes people to have an allergic reaction stays active for more than a year, Muffoleto said.
People should never, ever, ever burn poison oak. It can cause severe allergic reactions to the eyes and lungs and could be fatal.
It can be removed by hand, but shouldn’t be done by someone who has a high level of allergy to it.
“My wife looks at it and gets it,” Bennett said. “If you have a higher tolerance for it and are willing to dress for it, there are a couple organic ways you can do it.”
Hand removal — where you remove the entire plant, stem and root from the ground — can be done in late fall and early winter when there is no foliage. However, the oil is still on the stems.
Any roots can’t be left behind or it will come back, Bennett said.
Poison oak can also be managed by goats, sheep, deer and horses, who can all graze poison oak with no ill effects, Bennett said.
Goats are probably the best, and it doesn’t affect their milk, he said.
The danger of getting contact dermatitis from poison oak is highest in spring and early summer because the plants are still exuding oil.
It’s best to use gloves dipped in rubber that can be thrown away, when handling the plant.
Wash all clothing thoroughly, including shoes, after exposure.
According to the University of California, Integrated Pest Management Program, there are several herbicides that control poison oak, including glyphosate (Roundup, etc.) and the auxinic herbicides triclopyr (Garlon, Ortho Brush-B-Gon, etc.), 2,4-D (Brush Buster Woody Plant Herbicide, etc.), a combination of 2,4-D and dicamba (Spectracide Brush Killer Spray Concentrate, Spectracide Poison Ivy & Poison Oak Brush Killer, and Ortho Weed B Gon Max), or a combination of glyphosate and imazapyr (Ortho Groundclear Vegetation Killer).
People can apply some of these herbicides as stump or basal applications, but all are applied as a foliar spray.
Glyphosate is one of the most effective herbicides for controlling poison oak. However, it will damage or kill other vegetation it contacts.
Auxinic (selective) herbicides like triclopyr, 2,4-D, dicamba, and combinations of these herbicides also control poison oak. These herbicides can be applied earlier than glyphosate, when plants are growing rapidly from spring to mid-summer.
Triclopyr is the most effective auxinic herbicide for poison oak control. It has a wider treatment window than glyphosate, and it often gives more consistent control. Two formulations of triclopyr are available. Triclopyr amine is the least effective of the formulations and requires relatively high rates. Triclopyr ester or triclopyr ester plus 2,4-D ester gives better herbicide absorption into the foliage and is more effective.
When 2,4-D is combined with dicamba, it provides much better control than if it is used alone in a 1 percent solution. Premixed combinations of these herbicides are available. Dicamba applied at 0.5 percent gives better long-term control of poison oak than 2,4-D.
A new herbicide in California, imazapyr, also is very effective for controlling poison oak, but it is available for application only by licensed pesticide applicators.
Bennett said that people need to be careful when using chemicals because, eventually, it all goes into the water table and can be harmful to animals and people.
“People always think a little bit is good and a lot would be better,” and can over-treat an area, Bennett said.
There is an organic herbicide Bennett uses called Burn Out, which is a combination of clove oil and salt. People also can make their own herbicides out of vinegar and salt.
Diluted white vinegar and water is an “old time organic weed killer,” Bennett said.
If using chemicals, it’s best to do it early in the morning when there is no breeze to carry the spray onto other plants, he said.
Maintaining a healthy cover of desirable vegetation will reduce potential invasion as well.
Poison oak is the foothill flower “that keeps on giving,” Bennett said.
It can grow up to 1 foot a week in the spring, he said.
People should learn to identify poison oak, regardless of whether they are going to try to get rid of it from their yards.
If it has “leaves of three, leave it be,” Bennett said.
Each leaflet is 1 to 4 inches long and smooth with toothed or somewhat lobed edges. The surface of the leaves can be glossy or dull and sometimes even somewhat hairy, especially on the lower surface, the UC Pest Management program said.
In spring, poison oak produces small, white-green flowers where leaves attach to the stem. Whitish-green, round fruit form in late summer. In early spring, the young leaves are green or sometimes light red. In late spring and summer, the foliage is glossy green and later turns shades of orange and red.