I noticed that there is an American product by bug-be-gone and it is supposed to kill these.
One of the control articles I read said birds were a solution
You may have had a combination of birds trying to eat the worms and the worms eating the plants.
It is by Ortho and distributed by Scotts Lawn food products -- European Crane Fly Larvae is one of the things. it kills.
Says to apply in the spring or early summer.
