Karen,
>> Rick, have you ever tried iron phosphate for slugs? I've had really good results with it.
Yes, during the years that I lost every single Delphinium and lots of other seedlings and even Hostas, adult Swiss Chard and Bok Choy. And they crippled a lily that I only have one of.
It does work, I would say 1/4 as well as the metaldehyde-based slug baits. The difference is very dramatic when you have lots of slugs, and western WA has had a few years in a row with lots of slugs.
I saw ONE slug mow down an entire clump of baby Lobellia overnight, and when I don't bait, there can be over a dozen slugs on one small part of the deck, even at 8 am. Before I realized that slugs ate plants, I wondered if my neighbor was plant-napping seedlings ... but she would have had to have been AWFULLY fast on her feet to get 100% of seedlings in one night!
I don't think the breakdown products of metaldehyde in ground water are TOO bad (compared to many other things in wide use) but I use it sparingly, only around seedlings, only just after a rain, not in the rainy season, and in conjunction with lots of beer saucers. The beer saucers also let me know about slug population explosions, and then I get out the bait. An early warning system. There is some fancy name for matching the seriosuness of anti-pest measures to how severe the probelm is at the moment.
This year I noticed that zinnias were mowed down in preference to other things, as soon as i put them out where I don't bait. Funny - I've had Zinnias survive the slugs, but that must have been when they were near the Bok Choy, which the slugs preferred. Or they are different varieties of zinnias: "Oklahoma" and "Benary Giant" this year. Dozens of seedlings now swiss cheese. (Can you tell that I haven't reconciled myslef to living with slugs?)
I meant to try a trap crop of lettuce this year, but never got arouned to it (and had no leftover space in the beds).
Corey