Sluggo kills slugs and snails by poisoning their digestive system with iron phosphate, a naturally occurring compound. Once a slug eats the bait, it stops feeding almost immediately, then dies within about seven days. The pellets that slugs don’t eat break down into iron and phosphate, essentially becoming fertilizer in your soil.
How Iron Phosphate Kills Slugs
Iron phosphate works as a stomach poison. When a slug or snail consumes the bait, the compound damages the lining of its digestive tract. This damage is severe enough that the slug loses its ability or desire to eat. Feeding stops almost right away after ingestion, which means your plants get protection well before the slug actually dies.
Death itself is a slower process, taking up to seven days. During that time, slugs typically retreat to hidden, moist spots, which is why you won’t usually find dead slugs scattered around your garden the way you might with faster-acting poisons. This can make it seem like the product isn’t working, but if you notice less plant damage within a day or two, the bait is doing its job. The exact biological pathway that causes the digestive shutdown isn’t fully understood, but the end result is consistent: slugs eat, stop feeding, and starve.
How to Apply Sluggo
The standard application rate is half a pound to one pound per 1,000 square feet. Use the lower end for moderate slug activity and the higher rate for heavy infestations. At the lower rate, a single pound covers 2,000 square feet, so a little goes a long way.
Scatter the pellets evenly on the ground near the plants you want to protect. Don’t pile the bait in mounds. Spreading it out gives slugs more chances to encounter it as they move through the garden at night. Evening is the best time to apply, since slugs and snails are nocturnal feeders. If the soil is very dry, give it a light watering before scattering the pellets, because slugs are more active in moist conditions and more likely to come across the bait.
You can reapply as needed, but no more than three times within a 30-day period. Heavy rainfall washes away or degrades the pellets faster, so reapply after a downpour. If you’re using Sluggo around edible crops, stop applying at least three days before harvest.
Safety for Pets and Wildlife
Iron phosphate is far less toxic to dogs, cats, and wildlife than the older slug bait ingredient, metaldehyde. Metaldehyde kills slugs faster but is highly toxic to dogs and other animals that might eat the pellets. Iron phosphate products like Sluggo are commonly labeled “pet safe,” and while that’s broadly true compared to the alternative, the label deserves a small asterisk. These products can still cause digestive upset if a pet eats a large amount, so it’s reasonable to store the bag out of reach and avoid letting your dog graze on freshly scattered pellets.
The risk profile is dramatically different from metaldehyde, though. Metaldehyde poisoning in dogs can cause seizures and can be fatal. Iron phosphate, by contrast, poses a much lower threat. For most pet owners, switching to an iron phosphate bait removes the most serious danger associated with slug control in the yard.
What Happens to Unused Pellets
Any pellets that slugs don’t eat break down naturally in the soil. The iron phosphate biodegrades into its two components: iron and phosphate. Both are nutrients that plants use, so the leftover bait essentially acts as a mild fertilizer. This breakdown is one reason Sluggo carries an OMRI listing (Organic Materials Review Institute), meaning it meets the standards for use in organic gardening under the USDA National Organic Program. If you’re growing food organically or just want to minimize synthetic chemicals in your yard, iron phosphate fits within those guidelines.
How Sluggo Compares to Metaldehyde Baits
The tradeoff between iron phosphate and metaldehyde comes down to speed versus safety. Metaldehyde works very quickly, killing slugs in hours rather than days. But it’s toxic to dogs, cats, birds, and other animals that encounter it. Iron phosphate takes up to a week to kill, but slugs stop eating your plants almost immediately, and the bait poses minimal risk to pets and wildlife.
For most home gardeners, especially those with pets or children, iron phosphate is the better choice. The slower kill time is largely irrelevant in practice because the feeding cessation happens fast. Your hostas and lettuce get relief on day one, even though the slugs themselves survive for several more days underground. The only scenario where metaldehyde might seem appealing is a sudden, overwhelming infestation where you want visible dead slugs as confirmation. But even then, the plant protection timeline with Sluggo is nearly the same, and you avoid the poisoning risk entirely.