How to Control Wood Bugs in your Garden

Wood Bugs, Woodlouse, Pill Bugs, Roly-Polys, (whatever you call them) are rarely a plant pest. So why are you seeing them on your plants? And how much damage are they doing? (By the way, sow bugs are different, but related, and all of this applies to them as well.)

Once again, our gardening behaviours during the pandemic, has some in our industry referring to this pest as one of the “Covid Era Pests.” We see more bugs because we’re looking more often and we’re spending more time and tinkering more often in the garden. Wood bugs qualify as a Covid Era Pest because, while they have always been around, more people have more recently found them doing all sorts of garden damage and occurring in large numbers, and this is the direct result of composting.

We like to tinker. Seldom do home gardeners just throw a plant in the ground and walk away. No; Instead, we test and amend the soil, we mix in additives to change the structure, we fertilize, we baby them, we pretend they need us. And it is, very simply, the regular addition of compost that is leading to most of the problems with wood bugs.

Wood bugs are composters. They eat dead and decaying plant matter. They are important in our yard. Lots of things eat them too, so their numbers are usually in check. And while they live for a long time (a couple years) they don’t lay that many eggs and so their numbers rarely increase explosively.

Did you know wood bugs are more closely related to lobsters than other insects? Yeah, they are the only land-dwelling crustacean. They taste just as good too. Just kidding – don’t eat them. I have heard that they consume and accumulate heavy metals, which makes them better as compost themselves than as a meal.

However, in decaying compost, you will find that all sorts of critters and wood bugs of all life stages will be present. Take that compost and add it to clay soil, or other soil with less decaying matter and what you might end up with is a lot of composting bugs with very little compost. This is when they become a problem. There is little to separate dead plant material from living plant material – sometimes just an hour or two. So there is little stopping wood bugs from chomping that seedling, or eating that ripe fruit if they are starving and happen to come across it. Furthermore, there are plenty of other invertebrates that won’t harm plants except under certain circumstances. And one of those is during drought. If their food is too dry some may nibble on plants (especially stems) to get the moisture they need. So keep those gardens watered.

If you’re noticing this is resembling an online recipe, where you have to read the authors life-story before getting to the ingredients, that’s because I am trying to clarify one thing before I list the controls: You probably don’t need to control this pest. Pick your strawberries before they are over ripe and protect your seedlings or start them in plugs and transplant. Both of these are things you can do to ward off all sorts of problems. But nevertheless, here are the controls:

Trap Them

Place a moist piece of rotting wood, cardboard, a pile of fresh compost or fallen leaves in your garden. Wait 24 hours or more, then, scoop it up and remove it or add it to your compost (which should be far away). You can even sort through it to see what you’ve caught.

That’s it. That’s all the controls. Now you’re thinking: “Wait, what about ___?” So, let me identify a few other considerations:

Diatomaceous Earth

DE is a bit of a fraud. Sure it can work, but not if it gets wet and damp, like it does outside. And honestly, just make a ring of it somewhere your garden and put a wood bug in there and see if it keeps her in. Chances are she’ll just tunnel under it.

Chemical Sprays

Sure this works…you criminal! Just kidding. Again, these pests hardly need controlling so if you want to spray them dead then I want to know how they’ve upset you so much that killing their natural predators and everything else around them is going to make you feel better. But of course, there are times when steep measures are needed. But, there is nothing simpler than just feeding them compost so they leave your plants alone.

Crushed egg shells

Nope.

Prevention:

Even though trapping them with compost is easy, prevention is key. If you’re going to go through the trouble of placing a pile of compost in your bed to attract them, you could also give your bed a huge amount of compost (maybe even regularly adding recently dead plants (like your bolted lettuces) and leave it (and the wood bugs) there. Now you’re feeding them and they aren’t harming your plants, and the result is that they subsequently feed your plants available nutrients and you become best friends.

Conversely, you can also avoid using compost that isn’t fully broken down. What I mean by this, is the best compost for nutrient availability is stuff that has just turned into a dark brown goo. It’s moist, with fine particles. In this compost there are still tons of invertebrates and others breaking it down further, but the large pieces are mostly gone. The compost you don’t want if you’re worried about feeding Woodbugs, is one that still wouldn’t go through a loose screen because of chunks of wood or woody stems. This kind is still food for the bigger guys like wood bugs and moving this into your garden will not just attract them but physically move them, since they are likely to be in that compost.

Natural Predators:

Here’s something to haunt your dreams: The Woodlouse Hunter.

Yes, with mandibles like these, this spider looks like it could take down small to medium sized humans, but the truth is they are not dangerous, nor are there many documented cases of bites. Those mandibles (jaws) do have a purpose, and they are to harvest precious souls, but mostly those of wood bugs.

Woodlouse Hunters live underground or in places wood bugs tend to be, so we rarely see them, but they are very common across North America. They’ll eat other larger invertebrate pests and are therefore also important in your yard. So, instead of calling in an air-strike when you see one of these, just let it be on it’s way.

Snakes/Lizards

Yep. They eat them. And they eat all sorts of other pests. If you’re like me, in Canada, then there are few places where we can’t confidently handle a snake and throw them at our kids (I mean to our kids). So, they are great to have in the garden. Some of you are from countries where a snake in the yard could justify an air-strike, so I’ll leave this control up to you.

Wood bugs are really just one of those bugs that we see, and we recognize and so we associate all of our problems with. “What happened to my strawberries, wood bug?” “Where did my carrot seedlings go, wood bug?” “Where did I put my keys, wood bug?”

It certainly is a Covid Era Pest, since so many beginning gardeners are seeing them and wondering what they are doing. So, if you’re in that boat, please recognize how easy it is to avoid needing to control them, by simply not encouraging them. Ripe fruit touching the ground is inviting all sorts of critters, so avoid this by raising fruit off the ground, or picking them a day earlier. Adding compost to your beds will increase their numbers, so continue to feed them compost, or try older compost, or less of it. And start your seedlings in plugs because all sorts of critters will eat your seedlings. And enjoy the complexity of nature: If you have lots of wood bugs you’ll soon have lots of things that eat wood bugs.