I just came across this method and must say it fascinates me. Experimental biology AND slug control at the same time? Count me in!
First, let me describe my situation.
My main garden is about 5x15m (15x45 ft). I have a couple other experimental patches around the house. Mostly, I grow edible perennial bushes, a few vegetables, cereals and pulses. I have a 3x9m (9x27 ft) woodchip zone, a hügel bed, a straw-mulched flatbed and a woodchip-mulched half-hügel bed.
And I have big slug problems. They are in all garden beds and decimate squashes, sunflowers, amaranth. Rye (newly planted) and lentils also suffer considerably. Only favas and runner beans seem to survive, thought even runner beans have been wiped out of one of the experimental patches (nothing remains in that particular spot). The slugs mostly keep out of the big woodchip zone, thought it might be because I mostly grow sunchokes there.
I do have 3 tiny ponds sheltering tadpoles in the main garden area, but I expect they're too young to be effective yet. Indeed, the oldest one is barely a year old.
I have set up beer traps, and they do catch slugs, but it doesn't seem to be making a difference.
I have made tiny greenhouses out of PET bottles by removing the bottom and placing it on some amaranth plantings, but about half of them still got eaten.
I occasionally did go out at night with a pair of scissor, but it gets old fast.
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Main garden area. Greenhouse is south facing. The area is very close to both pasture and forest, which may or may not encourage slugs.
Now to the main point. I'm going to try that nematode-culture thing (by the way, they're named
Phasmarhabditis hermaphrodita) and see how it affects my situation.
I just gathered 40 slugs (didn't mean to catch this many but I couldn't stop) and have put them in a 4l (1 gal) can, along with a bit of water and buttercups. I'm going to wait 2 weeks and feed them as I go. I'll post back results.
As much as I love science, I can't really be bothered to set up a control area, so that'll still be anecdotal.
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Slug ghetto, one hour after harvest. Container was moved in the sunlight for the picture. I dare not remove the glass now.