Slug Control with Nematodes

A few years ago I bought some Nematodes to help control the garden slugs, and had good success with it. But, they were very expensive  to purchase, and they apparently didn't survive in the soil over the winter. So, they required annual purchase and re-application. So, since then I have been relying on Sluggo Plus to control the slugs. This year has been very difficult, though, due to the very wet spring we had, and the frequent rain since spring. Every time it rains, the Sluggo Plus must be re-applied since the water dissolves it, and it is no longer effective.  So, I thought of re-investing in some nematodes.

A fellow gardener asked if I ever "grew" my own nematodes, and of course I have not. So, he referred me to a video on how to grow them. Curious, I watched the video, went out at night and collected some slugs, and tried to grow some nematodes. This evening I checked the water under the microscope, and was pleased to see a number of nematodes in the water. I am going to leave it brewing overnight, and then apply it to the beds in early morning to see if I can reduces the damage to the lettuce, spinach, and swiss chard.

Here is the video that was recommended to me:

So, some slugs are naturally infected with this type of nematode, but not at a high enough rate to kill off the slug population in the garden. ?? I'm guessing that the nematodes multiply in the water, creating a sufficient population that can then be applied to the soil for higher efficacy?