Looks like the work of gypsy moth or the dreaded tent caterpillar. They can defoliate a tree in no time and they poop a doodle doo. Make a closer inspection for tell tale evidence. There are products available to deal with them. May be too late if they already transformed into moths. You have to get them at the larvae stage.

It is possibly the white ermine moth. We had similar webs on our beech hedge last year and this year no sign of them.
The hedge doesnt seem to have suffered any adverse effects.

The caterpillars are quite small and the moth is white with black speckles [about 1" long], rather a pretty moth.
WE caught several adults in the moth trap last year. so far just buff ermines this year.
The caterpillars [if not present in the webbing] will have fallen to the ground and will be pupating in the soil.

Unless you are growing commercially then I'd do nothing as they provide food for many birds and bats. Both need a helping hand to raise their young.
The moths also help pollinate many flowers.

They are a slithering, squirmy mass of awfulness and look like some terror from a Steven King movie, but your trees will survive and produce new leaves this time. Just give them a good feed and water regularly. Be ready for those boogers next year.

Yes it is sad that they are portrayed that way in movies but they are intriguing and amazing feats of nature.
chances of seeing the adults laying eggs next time is very unlikely unless you sit out all night. These moths are night fliers. ;o)

They could be scary for someone unfamiliar with them. They do remind me of maggots

SBG, always great info. Thankyou.