Beneficial nematodes (Steinerma carpocapsae) act as a parasite in pre-adult, pupal, and larval fleas, keeping their populations under control. They’re also used to control grubs and fungus gnats, but I’m not concerned about them. I’m concerned about my poor itchy dog, and having an uninhabitable house. We’ll see. At 40 dollars, I hope I haven’t wasted my money.
This variety of nematode is a non-segmented roundworm that enters the flea through it’s orifices or directly through the exoskeleton. The nematode then expels bacteria inside the body of the flea, causing blood poisoning in the flea, and killing the creature. After this, the bacteria works on the flea’s insides, turning it into food. The nematodes use the fleas shell to reproduce as well, and once they’ve eaten up a flea’s innards, they all leave their host, and hunt for others.
The nematodes arrived in the mail with an ice pack to protect them, so I've had them in the fridge for about a week. They come in a sealed plastic bag and they are suspended in a beige paste that is smeared on a narrow, rectangular sponge and then folded. The directions tell you to use two containers of lukewarm water into which you put the sponge. You then squeeze the sponge to get all the nematodes into the water, and combine the two containers of liquid into one. We used a watering can, and sprinkled them everywhere we've seen the lounging deer. The nematodes need moist conditions, so we watered where we sprinkled the nematode juice, and now we wait...
In case you're interested in more information, here are some links: