Apply Wire Mesh For This Parging Patch Job?

Going by the rust on your lath, you should probably just tear it all off and start over. At the least, you need to cut it back to non rusted lath.

Tscarborough said:

Going by the rust on your lath, you should probably just tear it all off and start over. At the least, you need to cut it back to non rusted lath.

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Ack! Say it isn't so ...

At least cut more of the concrete back to expose the lathe.
Like any patch job, even drywall, you need to spread it out and blend it in to make it disappear,

I would use a 4" grinder and a diamond wheel on it to cut back the concrete to where the wire is solid. Cut with grinder and break out with hammer.
Seems like all the rust would be right where the opening is and where water got in.

Then attach new wire to solid wire, just because old wire turned brown, I would not say is unusable for a patch job.
Either way you want to open it up to bury new wire and not just nail it on surface over old hole.