Hi Heather,

Poison Ivy is certainly a stubborn plant.  It can take repeated treatments to eradicate it.

I understand your worry that you may damage your winterberry bush if you try to use a paintbrush to apply a poison ivy killer.  An alternative method would be to cut the poison ivy stem near the soil surface and paint the stump with a more concentrated herbicide formulation.  Be sure to read the instructions on the label of whichever herbicide you select for details on how to use the product in the safest and most effective manner possible.

When removing the poison ivy plant (while wearing gloves), collect all of the above ground plant parts and bag and dispose of it in your garbage. After you've removed the plant, you can spread clean wood chip mulch over the site to prevent possible exposures to urushiol that may remain on or in the soil.  

I've included an excellent information sheet on poison ivy that you may find helpful.

Toxicodendron radicans (Eastern Poison Ivy, Poison Ivy, Poison Oak) | North Carolina Extension Gardener Plant Toolbox

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