Rinse the foliage immediately. A lot.

Ditto. Hose it down IMMEDIATELY.

If it is a deciduous tree and only a small part of it was hit by weed killer, cut off those branches immediately. Like now.

you will need to thoroughly saturate a vast majority of the tree.. to kill it ...

and i cant tell based on your words ... how much you really sprayed ..

it would also help to know what you used ... and how big the tree is ...

when i spray for weeds in the garden beds ... i use extremely low pressure.. which creates drops.. which fall to the ground ... even in some amount of wind ...

thats your exploded and sprayed wildly.. suggests to me ... that you where using way too much pressure ... this stuff isnt french perfume.. you dont need to atomize it ...

take the time to play around with your sprayer ... filled with water .. and learn how to adjust pressure.. and the nozzle ... to create the drops i am suggesting ... its worth the time ...

all that said.. all you can do.. by now.. is wait and see what happens ...

ken

What did you use as the weed killer?

Exactly^....what material was this? That is the obvious first question we need answered.