SLUG IPM

Slugs!

I have lost more garden plants to slugs than all the other pests put together. I’ve lived in the swampy maritime western Oregon all my life and slugs are the goblins of my existence. Every year I feel like Beorn as I battle back their numbers to protect my garden from desolation. Sometimes they get through, but I’ve gotten pretty good at managing their destructive hordes.

These animals are ubiquitous in our region and cannot, nor should they be, completely eradicated. Any attempt to do so will create a slug vacuum into which nearby slugs will be pulled the moment whatever toxic sludge you’ve spread is neutralized or washed away. It’s not worth the health risk or expense.

A reasonable goal is to hold back their numbers until our baby garden vegetables and flowers can establish themselves. Most of us are planting out in late March, April, and May – the height of slug activity levels. This plan mainly focuses on slugs, since I don’t see the European Garden Snail in our yard.

Before we get into the nitty-gritty of the IPM protocol, I’m going to summarize my strategy and how I implement it.

My Slug Control Plan in Action

Late February:

These three chickens did a fabulous job of working over the leftover mulch, removing the insect burden. There was nary a slug to be found.

Remove all the mulch and debris from my garden beds. I winterize with old leaves, crop residues, and a little finished compost. Whatever hasn’t fully been processed by bugs, slugs, and worms gets pulled off and added to the composters. This leaves my soil bare (gasp!) and exposed to sunlight and wind that helps to dry the top of the soil. If I had access to chickens and a tractor cage, I would begin process now.

Start chemical controls including beer traps and Sluggo. Use Sluggo sparingly, about 1 pellet every six or so inches. To make a beer trap, sink a plastic tub into the soil leaving the rim about a half inch or so above the soil line to keep our beneficial ground beetles out. Clean it only when it starts getting full, because the more slugs in it the more they seem to like it.

Two young slugs in cardboard shelter trap.

Place shelter traps. These can be down-facing halved grapefruit rinds, cardboard, rocks, etc. On a sunny day, lift the traps and hand-pick out the slugs and drop them in a tub of old beer. On rainy days, it’s easy to go out and pick them up everywhere. Remember the goal is to bring their numbers down, not total eradication.

April:

Plan for losses when starting seeds. If I want four broccoli starts, I’ll do eight. A few may die during the starting process and I may lose a few to slugs or other pests. When transplanting, or a few days after direct sowing, I’ll refresh the Sluggo to give the vulnerable veggies better odds. I usually end up having leftover starts, which I like to share with my neighbors and friends.

April, May, June:

Plants are the most vulnerable at this young stage, which unfortunately coincides with the height of slug activity, so I keep up with my control strategies until mid-June. By then the weather is warm and dry and my plants are sturdy enough to tolerate some nighttime nibbles. After that time, my primary control measure is watering in the morning. However, if we get a rainy week in the summer, I’ll patrol and hand-pick those that are taking too many of our strawberries.

Summary:

Feb-March: Remove mulch. Set out beer traps. Set out shelter traps. Lightly Sprinkle Sluggo. Start indoor seeds and double what I need.
April: Begin sowing seeds double. Once a week, refresh Sluggo and beer traps. Monitor shelter traps.
May: Set out starts. Be vigilant for a week or so until they get established. Hold on to one or two extra starts to replace ones that die.
June: Water in the AM only.
Rest of the growing season: Accept losses or damage and let plants fend for themselves. Studies show that plants are very good and fending for themselves and some even send out chemical signals to attract predatory insects to your yard. (Read More)

Official Slug and Snail IPM Plan for SBG

What is IPM? Integrated Pest Management is a process of studying the animal or disease in question to understand its life cycle, habits, place in the ecology, strengths, and vulnerabilities. This information is then used to create precision plan to control the pest’s effect on a crop, by using physical, cultural, biological and chemical control methods. The goal is hyper-specific control measures with the least amount of collateral damage to the local ecology.

It’s a whole thing, so if you don’t have the time and energy for that, (I feel you!) please come back and use my IPM plans as often as you want. I plan to add one for each of our most common garden pests.

The first step is to know what you’re dealing with and make a proper identification. This article by Oregon.Gov is an excellent place to start: Slugs and Snails in Oregon

Friendly Gastropods (Not our Enemy)

Oregon Banana Slug

Banana Slugs: Our pretty, yellow and black banana slugs are usually forest dwellers and are really not a problem for most gardens. Any that slide into your garden will appreciate a ride back into the forest.

Native Pacific Sideband Snails: You can recognize these guys by the shell that lays somewhat flat on their backs. These little ones are actually predators and prey on other small gastropods. Yay, native snails!

Glass snail. Slug predator. Non-native.

Glass Snails: These tiny little blue snails with translucent shells are not native. However, they don’t cause much damage to my crops and they also eat slugs so I can’t bring myself to harm them.

Great Gray Garden Slug: This guy has racing stripes and spots. It will chase down and eat other gastropods, but it will also eat your garden as well. I leave these alone as long as they are not actively munching on a young veggie.

The Enemy

The following critters have a special affinity for munching on our garden veggies to the exclusion of the profusion of other plant life. Much of the time they simply chew the stem and fell my tender young veggies like trees, leaving them to die as they move on to the next tasty stem.

Typical slug cavity.
European Garden Snail.

European Red Slug:

These are a dark red/brown color with a reddish skirt around their base. These can get quite large with an appetite to match.

Gray Garden Slug:

This is a small mottled colored slug and does grievous amounts of damage to our gardens. I find these wrapped around my strawberries a lot. I find young ones spending the days in cavities they made in my strawberries.

European Brown Garden Snails:

These cute little guys hitch-hiked from the old country and have naturalized themselves here. They have a large, upright shell that looks faded. They are generally bigger than our native snails.

About Slugs

Life cycle of Slugs: They are hermaphrodites. They lay clear opalescent eggs (smaller than a BB) in clusters up to 80 up to 6 times a year. They are laid in moist dark areas. Under boards, leaves, rocks, and other sheltered spaces. They hatch after about two weeks to a month. They reach sexual maturity at xx days and can have xx many life cycles per season. They go dormant during hot/dry spells by encasing themselves in mucus in a protected crevice. They also hide and become somewhat dormant during cold spells. (OSU: Life of a Slug)

Activity: Evening through morning. Although they will stay active during gloomy, wet days when they are protected from the sun and drying out.

Willamette Valley Gardeners: beware from February through June. Hot dry summers force them to retreat to a semi-dormant state and mature plants can defend themselves.

Humidity: These mucus covered gastropods need high-humidity to cruise the land. They are most active after dusk until just after dawn. Slugs are everywhere on an early morning walk, but hiding under litter during the day. Unless it’s raining. Then it’s an all day and all night party.

Cultural Controls

These are things we can do to discourage slugs making our property their haven. Knowing they need humidity and shelter for the sun we can use that against them.

Encourage areas to dry out and warm up. In late February and early March, remove all leaves from your garden beds. Remove all hiding areas near your garden beds as well. That means, leaves, piles of boards, buckets, or anything that provides shelter from the sun.

During the dry season, water in the morning to ensure your bed surfaces are dry by nighttime. Providing moisture at night when they emerge from hiding is like laying out a welcome mat.

Barrier: copper tape around a pot or bed frame reacts with their mucus covered bellies giving them a zap that makes them turn around. I use copper tape on my pots.

Physical Controls

These are things we can actively do to manage their numbers. They need shelter from the sun and humidity. If we provide those conditions they will go there, then we can remove them.

Traps: Leave grapefruit rinds (or other fruit rinds) around in your beds. The slugs will go there to hide during the day. Check a few times a day and remove the slugs. Dampen an area and place wet cardboard or an old piece of plywood under a board or cardboard. Check daily and remove any slugs and eggs you find.

Patrol: Go out after dusk with a flashlight and pick them off your plants.

Disposal: I tend to be a flinger, but I’ve read that slugs are territorial and will return. So instead, try dropping them in a tub of alcohol laced water (soapy water doesn’t harm them) or if you can stomach it, cut them in half with scissors. Salt can harm your soil and inflicts a lot of suffering on the animal before it dies. It is much kinder to drown them in old beer. At least their last moments are happy ones. Cheers, slugs!

Biological Control

This control involves using natural slug enemies to control their numbers. This could be bacterial, fungal, or other animals.

Before chicken tractor
After chicken tractor

Ground Beetles: These friendly black beetles are voracious eaters of slugs, symphylans, and many other garden pests.

Native Snails & Glass Snails: These tiny snails will chase down and eat slugs. I’ve seen it, it’s impressive to see this tiny animal actively deflating a much larger slug with its probicious.

Ducks in general like to eat slugs. If you have them or can borrow from a friend, let them cruise your garden beds after removing the mulch. They drop decent fertilizer too. Win-win.

Chickens can be trained to eat slugs, but in general don’t seek them. If you have a flock it might make a useful disposal strategy. Chickens in a tractor do a fantastic job of eating everything that moves or doesn’t as well as giving the soil a light till and of course eggs. They make great bed preppers in February through March. We used three chickens for one week on each bed. (I like to rake the soil and give the manure a couple weeks to break down after chickens have worked the bed over.)

Garter Snakes in a nearby wetland area.

Garter Snakes: These cute little critters are happy to keep your slug populations down. However, most of us suburban gardeners aren’t lucky enough to have them. If you do, make a pile of large rocks near your garden to attract snakes. They appreciate the ambient warmth of a rock pile at night and early morning.

Chemical Control

Beer Traps: Beer traps are technically a chemical control because of the fermentation, but they are not harmful to the ecology. Place a tub just above soil level and fill with the beer that had a cool label but turned out to be gross. Keep it above the soil line so our ground beetles don’t fall in.

Sluggo: The active ingredient is iron phosphate which is naturally occurring in the soil. The trick with Sluggo is not to use too much. One pellet every six inches or so is plenty. Birds and worms are also known to eat Sluggo pellets, but an OSU Extension study shows it is not harmful.