How to irradiate?
From the reading and research I have done, there is some experimentation being done on microwave irradiation of weeds. I found a 170 page PhD thesis on this topic and briefly skimmed through – very technical and designed for farmers who want to clear fields, not the average homeowner with a modest-sized yard. The following short article talks about irradiation and lasers being scrapped in favour of electrocution of weeds. Again, this research seems to be targeted at commercial growers.
There are a number of ways for the homeowner to get rid of poison ivy:
1) Pull the plants out, trying to get ALL the root. Wait until after a good rain, wear long pants, long sleeves and heavy gloves and get as much of the root as possible. When it inevitably regrows from tiny pieces of root, cut off the plants at ground level and eventually you will starve the plants of nutrients and they will die. Be careful not to touch anything that has come in contact with the plants, like the work gloves, with bare skin as the oils giving rashes can easily be transferred that way. Don’t let your pets roam among the plants as petting them later can give you a rash. Dispose of the plants in the garbage, not the compost bin.
2. Solarization – cover the weeds with clear plastic and weight down the edges so the plastic is tight and won’t blow away. Leave the the plastic for 4-6 weeks and the heat from the sun will kill whatever plants are underneath the plastic. You could try this now, but I wonder if it isn’t too late in the season for this as it depends on a hot hot sun.
You may find this Toronto Master Gardeners Guide to Poison Ivy useful as a resource: https://www.torontomastergardeners.ca/gardeningguides/poison-ivy-a-toronto-master-gardeners-guide/
Good luck with this daunting task and work carefully!