My garden was plagued with slugs for many years and believe me, I tried evrything you suggested. The last and best product/method I used was iron phosphate granules.
It was amazing. The slugs went right for it. In fact I would set a little granule about three or four inches away from one of the little guys and then watch it go right for it and then devour it! I was sold. This stuff works.
I followed the label instructions and made sure I had enough to scatter in the fall when the next summer's slug eggs are actually laid. In the spring I had significantly less slugs and with a couple more scatterings, just a few last summer. My garden was glorious. It's like it had all that saved up energy from the years of chewing and it just burst into bloom.
The other slug treatments just dehydrate the slugs. They seek water or moisture but return to your plants. Iron phosphate is the way to get rid of them for good.
>> Is iron phosphate readily available in stores and how is it packaged?
One brand is "Sluggo".
I found the metaldehyde baits much more effective, like the next morning there would be many dead slugs visible.
But the iron phosphate bait did reduce their numbers somewhat, gradually. In my part of the PNW, we have 8-9 months of constant moist weather.
I found beer saucers almost as effective, and they "last" longer than bait when it rains 4-5 times per week.
But with either approach, as soon as the bait is wet or the saucers dry, there are huge numbers of slugs remaining. I just pulled a head of Bok Choy with many holes in its leaves, which i'm used to. But even after rinsing the whole head, I found FIVE SLUGS clinging to the leaves. YUCK!
Even that isn't as bad as they way they way they kill EVERY Delphinium seedling I put out, and 80-90% of anything else they like. Two years of trying resulted in ONE survivng Delphinium.
Tried the beer traps, and while mildly effective, are quite nasty to deal with. I've chosen the iron phosphate (IP) route and never looked back. Extremely effective when used correctly and with a little patience. My hostas love me for it.
The IP baits such as Sluggo (trademark name), and the newer version of Sluggo Plus (I think) also takes out pill bugs or rolly polly's whatever your name for them. Sluggo or similar IP products can also be purchased in bulk of 5, 10 and 20 pounds cheaper than the retail store over the net. Green Light brand also has a good IP product. They are all similar concentrations, just produced under different names. Every garden center or retail store should carry it in my opinion, but they often don't.
The IP does not not kill them right away, but over a three day period or so. You won't get the satisfaction of finding dead slugs like metaldehyde baits, but you can rest easier knowing their are no toxic poisons left behind in the soil. The IP is a naturally occurring element in the soil, but not in high enough quantity to affect them. The IP will disrupt their digestive system and they go back to their hiding spots and slowly "starve" to death. It will last for several days even with light rain or sprinkling, barring a heavy rain or prolonged sprinkler system times.
The directions say they are most effective at night before or after a light sprinkling to raise the moisture level and encourage them to forage. I've used it for over six years and rarely see a slug. At first sighting, I broadcast another light course. First dosing I broadcast rather heavy, and then follow up with a second lighter dose two weeks later when previous generations eggs hatch. A routine dosing is best if you are in an area that is prone to large infestations. Be sure to apply liberally in the areas that may be dark and damp, rock borders, heavy mulching, wood piles and around the foundation for example.
I also toss it over my neighbors fence and beds close to my yard to widen the circle of protection. I highly recommend iron phosphate baits.
>> The IP does not not kill them right away, but over a three day period or so.
That's reassuring. Never seeing dead slugs with iron phosphate, but always seeing lots of live slugs for the first two years I used it, made me think it was not doing much.
But I also think those the worst years for slugs around here in ages, and I was stilllearning how to deal with them, and did not yet use beer saucers.
>> I've used it for over six years and rarely see a slug. At first sighting, I broadcast another light course. First dosing I broadcast rather heavy, and then follow up with a second lighter dose two weeks later when previous generations eggs hatch.
We may have different circumstances. My slug infestation varies from "extremely heavy everywhere" to "only destroying SOME varieties of plants". And most of the yar, it rains so much that puting out during a rare "dry" spell is they only way to keep it form being rained on so heavily that it "mdelts" in a day or so.
It may or may not be factor that my yard is tiny so that "slug migration" assures I'll always have slug immigrants.
But during my summer, when we have little rain, I would agree with your comment that a light sprinkling of rain encourages them to forage, at least to do so more visibly. During this summer, I have left a few of the pellets lying around in welcome dryness, waiting for a damp day and more slugs.
It has been the lightest slug infestation for years, either because of the beer-and-bait, or cold weather. They only ate ALL my Zinnias and most of my Bok Choy, and a few pots of Lobelia instead of most of most things.
>> A routine dosing is best if you are in an area that is prone to large infestations.
I bet you're right, but I haven't figured out what to do about rain 3-5 days per week 8+ months per year. If I ever get portable hoop tunnels built, I may use those as rain umbrellas, keep seedlings under the plastic, and keep beer and dry bait under the plastic also.
I agree that beer saucers with dead slugs are yucky, but only a little more so than multiple slugs visible even during the daytime, or bringing a head of Bok Choy indoors and finding 5 slugs clinging to the innards!
This spring, I put out saucers very early, and gloated over catching dozens of the little #$%&@s in one night. Then a cold snap the next day froze the beer, and I had slugsickles or slug cubes for several days until they thawed.
Great article! I often wondered why not all slugs look the same.
It sounds like IP is for me, too.
I had a bad infestation of slugs and snails in early summer. A friend once told me she kept her garden weed free by spending 15 minutes each day weeding, so i thought i'd do so with them. I ended up spent nearly an hour each morning, filling a 1l milk carton with these slimy creatures, while cringing at the glamorous less job. It took several days, and now there aren't many of them around.
I'll try the ip next spring, a more profitable method than this hard labour work :).
Why not assemble some slug bait houses using small scraps (6-12 inches) of boards and load the bait in them?
Make some three or four sided tunnel type boxes. Even open ended cans might work to prevent the rain from
I'm sure you can find some creative methods like these.
Down here they are mainly night creatures - so I usually spread it in the evening. You might dose lightly after a rain.
At this point, we wish we could remember what rain is!
I like the idea of open-ended cans, unless the slugs avoid the metal. I've read that slugs won't cross copper strips.
I have plenty of plastic tubs and lids. I think I'll cut some doorways into them and weigh them down so they don;t blow around, then put bait udner them to stay dry. That way, I'll replace it less often and use less overall.
Thanks, that's a great idea!
I had been thinking along the lines of cold frames and plastic hoop tunnels , but something the size of a shoebox or deck of cards is much better!