Nemesys Vine weevil stuff

Simple question really. Do these nematodes survive in the soil until there are vine weevil grubs present. If so then for how long?
I have pots of Saxifrages which are clean at the moment but since they are alongside grubbed ones, it won't be long. No point pouring the stuff on them if the worms die without grubs to feed on.

 

Usually they tell you the best times to apply.
I've never used it but I have a sneaking suspicion that they don't survive in the soil for long without a host.

 

Ask the supplier. I ordered from Nematodes Direct some years ago and they were very helpful.

I don't think there is a way to tell if the Nemmies are alive in the soil as they are sort of small