If you have rotting pears all under your pear tree the solution would seem to be to get rid of them, ideally before they start rotting. Honest.
No chemical spray is safe for livestock, although they differ in toxicity (how bad and for how long). Don't let people tell you that glyphosate (roundup, etc) is harmless after 24-48 hrs, btw, that's basically in LAB "best case scenario" type testing, not the way it behaves in the real world.
I'd say dig the weeds by hand or put up with them (remember that most lawn weeds stay greener longer in droughts than typical lawn grasses. Also many have purty little flowers, and no I am not really talking about dandelions in particular <g>. Nature abhors a monoculture. Either spray toxic chemicals around til the end of time, which isn't good for you or your animals or the groundwater, or just accept that lawns have biodiversity
Patches of some especially obnoxious weeds (around here, it's things like goutweed, ground ivy, bindweed, thistle) you might want to smother the area under a thick layer of mulched-over cardboard for a year or two and then reseed or resod (herbicides won't do much against that sort of weed anyhow!)
JMO,
Pat