Pest control: introduction and slug control

By Jeff Begin
July 3, 2022

Introduction

Other posts in the pest control series:

• Rabbits and woodchucks
• All about row covers in the garden

Every gardener knows the pain of coming out to your carefully tended garden only to see a plant chopped off at the stem, ripped to shreds or leaves full of holes.  I know the pain all too well; it can be very disheartening and demoralizing.

There are plenty of solutions on the market and many of them effective, but a whole lot that are worthless.  I've wasted so much money on things that don't work, I don't really want to think about it.  An additional challenge we have on the farm is the limitations of growing organically, without pesticides.

But there are solutions to organic pest control.  There is a learning curve but push through it and you'll come to realize it's not all that complicated, though it can require effort at times.  This will be a series of blog posts to help shorten that learning curve, and I'll link them all together.

If you're an experienced gardener, maybe you'll find something new or please comment at the end to share your experience and helpful tips!  I'm always learning as well.

A word about product links.  I link to several products in this series of posts but am not affiliated in any way with these sellers.  I've bought their products with my own money and I find they work for me.  If you shop around you may find similar products from other sellers for less money.

Slugs

One of the main crops at the farm is lettuce, it's grows year-round.  As anyone who's tried to grow lettuce in the field or garden knows, one of lettuce's main enemies is slugs (heat being the other).

Slugs are hard to control and the only real defense is to create an environment where slugs don't want to be.

Eliminate slug habitats

This is the first step and the most worthwhile investment of time.  Get rid of slug habitats at least 5, maybe 10 feet away from your slug-sensitive crops.  The more the better.  Slugs like cool and wet conditions.  They hide in the daytime and come out at night, especially when it's damp.  In brief, keep your beds, paths and fencelines tidy.

Eliminate untidy areas like this one:

That is a slug resort!  In this case, it's for a bed of corn that's still small which I've found slugs leave mostly alone, so it's not a big deal here.  But if this were a bed of lettuce or some other green?  The slugs would hide in that mess of grass and weeds, come out at night or when it's damp and eat through the plants within several feet of that mess.  So get rid of it - pull it out and put down well-rotted wood chips to make it a path.

Same goes for any overgrown area or pile of organic matter - slugs will hide in them and come out at night.

Choose your mulch carefully

So alright, get rid of slug habitats, no problem you say.  But what if the mulch that you put over your bed and right under your plants is itself a slug habitat?  Choose your mulch carefully!

To be brief: only use well-rotted/decomposed organic matter as a mulch, 2-4" deep.  Slug's role in nature is to clean up decomposing organic matter, by eating holes in it.  So don't use decomposing organic matter as a much - use already decomposed organic matter!  The farm here is a deep-compost no-dig setup, so our mulch is compost.  I make sure the compost is well-rotted and mostly finished breaking down before I spread it.  There's no fresh or partially decomposed organic matter, only a semi-fine compost where everything has already broken down.  Slugs don't seem to like living here. Here's an example of good compost slugs won't like:

It's well rotted, dries out well and is crumbly/friable.  This is bought compost, which I purchased from Amherst Earth Products.

Another advantage of compost is the top layer dries out quickly in the summer sun and slugs don't like dry conditions.  If it stays wet for days on end, you may see an uptick in slug activity, but if your compost is well-rotted already you may not.

Avoid these mulches if you want to keep slugs at bay:

• Straw and hay - these are basically fresh organic matter and slugs will move right in.  They'll live in the bottom, damp layers.
• Leaves, dried or green - these are great additions to the compost heap, but don't put them directly on the garden bed without composting them first.  They'll become a slug habitat.
• Grass clippings - same as dried leaves: great for the compost heap but not directly on slug-sensitive garden areas.
• Bought wood or bark mulch - like from Home Depot or the local landscape materials supplier.  I find these are only beginning to decompose and will attract slugs.  Bought compost is usually okay, though.
• New wood chips - if you're going to use wood chips, let them rot for six months to a year first.  Even then, I wouldn't put wood chips on a garden bed as they may cause other fertility issues, but using them on paths is great.  Quick tip: if you buy chips from a local tree company, buy them in the summer so you get a lot of green matter.  That will help break down the wood chips faster.

Keep your garden tidy

This is where the plain ol' effort and time comes in. Keep your garden relatively weed free and neat around the edges.  Some weeds are unavoidable, but you want to avoid a jungle of weeds, that'll give cover to the slugs.

Pick off yellowing and dying leaves or any leaf sitting on the ground.  These will provide food and cover to slugs, and they're not helping the plant grow anyway, so remove them and compost them.

Unhealthy plants attract more pests

In my experience plants that are unhealthy, struggling and yellowing will attract all kind of pest, insect or slug.  If you have a plant that's not doing well and it's getting eaten, just remove it, it's bringing pests into your garden.

Eliminate raised bed sides

Especially wooden raised bed sides.  The wood keeps a layer of moisture nearby (usually) which slugs will like.  This is especially true for any wood that is decomposing.  Pressure treated lumber or other materials are a better choice though may still harbor slugs.

Try using a mound instead, 4-6" high of material.  This is particularly easy in a no-dig system, but if you have traditional raised beds this may not be an option.

I don't have a ton of experience with raised beds, I used them for a few years long ago but not recently.  Share your experience in the comments!

Water carefully, let things dry out

Be careful how and when you water.  Overhead watering, like with a sprinkler or a hose, can spread moisture over a wide area, not only where your crops need it.  This can keep slug habitats wet, which will keep them happy.  If you let things dry out, slugs will be less of an issue.

I use 5/8" drip tape to water my beds, and it delivers water only where I need it.  Paths and surrounding areas remain dry.  This is the drip tape I use, and that's where I ordered it from so I can recommend that.  I'll write a future post about setting up a drip tape system that's flexible and convenient.

Products to try

Products like slug bait or beer traps are usually last resorts, though they can definitely help.  I have used Sluggo in the past, before I figured out how to control slugs, and it definitely does knock the population down.

I found it worked best if I applied it early in the season before they started to reproduce, and kept applying every few weeks.  I was able to stop using any products at all by taking the steps above, so I'd view this more as a band-aid than a permanent solution.  But it can save your crop for sure.

I've also used slug beer traps before, but you really have to refresh them every day or every other day and I could never keep up with it.

Grow crops slugs ignore

If all else fails and you're just done with slug-prone crops (I feel you, believe me), then don't grow things slugs like!  There are plenty of options.  A few crops I've never had slug issues with:

• Tomatoes
• Peppers
• Cucumbers (if you keep them off the ground)
• Eggplant
• Onions
• Garlic
• Peas
• Green beans or shell beans
• Potatoes (they will eat the tubers, so don't leave them in the ground too long)

I'm sure there are others.

Here are a few crops that are prone to slug damage:

• Lettuce
• Brassicas - kale, broccoli, cabbage, etc.
• Small fruits, especially strawberries
• Beets
• Some tender squash, like zucchini

Good luck, fight on

I hope this has been helpful.  I'm not a biologist or any sort of certified expert, this is just based on many growing seasons of experience.  If I wrote this article again in five years I'd probably change some things and have more advice.  That's gardening, it's a never-ending learning adventure.

So please share your experience and helpful tips in the comments to help out others!

I'll continue this series in a few days to focus on another pest, let me know in the comments what kind of issues you have.

Good luck out there.