Poison ivy is a tough, tenacious weed that causes an allergic reaction (blisters and rashes) in 85 percent of the population. Getting rid of the weed can be extremely difficult; poison ivy often intermingles with other plants, and its root system can stretch for yards. Treating it with weed killer is often the best way to get rid of it, but you must apply the herbicide carefully and refrain from touching the weed itself.
Types of Herbicides
Purdue University's Department of Horticulture recommends using weed killers containing amino triazole or glyphosate, both of which are effective at killing poison ivy. Amino triazole is sold as Amitrol, while Roundup, Kleenup and similar brands contain glyphosate. Purdue also recommends a combination of 2,4-D and Banvel; however, these herbicides could damage nearby plants nearby if they are not carefully applied.
Because poison ivy will likely cause an allergic reaction if it comes in contact with bare skin---and because weed killer can cause burns and rashes---gardeners should wear protective clothes when applying herbicides. Wear gloves, a long-sleeved shirt, sturdy pants like blue jeans and work boots with long socks.
Apply weed killer when poison ivy is in full bloom---the leaves should be visible and pale to dark green in color. Apply the weed killer during still days so that the substance is not dispersed by the wind. Wait for a dry period with no rain in the forecast for a few days; otherwise the weed killer will wash off before it can do its job. Because poison ivy is so resilient, you may need to apply the weed killer several times before it has any effect.
Weed killer can damage plants you want to keep, so if the poison ivy is entwined with other plants you'll need to apply the herbicide with special care. The best method is applying the weed killer with a small brush or a cotton swab, painting it onto the leaves and the branches of the poison ivy. Another option is to saw off the top of the ivy plant (about an inch or so above the ground), then apply the weed killer repeatedly to the stump. Both methods keep other plants in the area safe while killing the ivy.
Once the ivy is dead, pull it out of the ground and wrap it carefully in plastic bags. Wear your long-sleeved shirt, pants and gloves while doing so---poison ivy can still cause rashes months after it dies. Make sure every part of it is covered in the plastic, then throw it away. Never burn dead poison ivy; the urushiol oil on the plant will create toxic fumes when it burns.