IMO, the asphalt patching products and 'sealers; (many, nothing more than latex paint) perform poorly. Consider contacting a firm that does asphalt driveways.

You can buy asphalt for patching at Home Depot or Lowes so you don't have to buy a large quantity. I used it to patch several holes in my driveway. I agree with Randy427 as to how to do it. I added one other thing; I used a blow torch to melt the patch in so it was smooth with the existing asphalt. Otherwise it will look like a patch. You probably could just let it melt a little in the summer sun and blend it in. It really wasn't hard to do.

Hopesprings, You cannot just replace one pane of glass, the entire IGU needs to be replaced. My comment as to whether I would not be sure about replacing an IGU in an 18 year old Hurd has to do with what I usually see as the observed condition of 18 year old Hurds. If the windows are otherwise in good shape, replace the IGU. You are certainly in the minority though with having 18 year old clad wood windows being in good shape. Props to you for obviously maintaining them if that is the case.

I don't believe the exterminator's story about mice digging down to enter through that opening but if you believe him and want to do something,here go's. Use urethane or Portland product to adheare STAINLESS STEEL screen that cover's opening. Too much trouble? Cover opening with spray foam mixed with stainless steel wool.