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Biological Diversity in the Garden

by Dawn
predatory wasp

Why You May Want the “Bad Guys” in your Garden

Warning: Today’s post is going to be something of a rant! Hopefully, an intelligent and well-reasoned rant, but a rant nonetheless. Read on at your own risk.

Why? You may ask. Don’t worry, I’m going to tell you!

I’m in several Facebook groups dedicated to raising swallowtail and monarch butterflies, and to growing milkweed in the home garden.

In two of these groups, people are constantly discussing how they’re going to eradicate every bug that preys on their caterpillars and butterflies, while in the other, no talk of any type of pest control is ever accepted, and is grounds for immediate removal from the group.

Neither approach makes sense. Let’s see why.

Eradicating Every Bad Bug

Let’s start with the “I’m going to murder every single bug that will prey on my caterpillars” camp.

Praying mantids will eat butterflies and caterpillars, and even dragonflies have occasionally been caught mid-feast. But it’s an undeniable fact that both species also eat LOADS of mosquitoes. So, a few sacrificed monarchs or a couple thousand mosquitoes? You decide.

Another example: Tachinid flies are small, kinda creepy-looking houseflyish things with big red eyes. They prey on monarch and swallowtail caterpillars, and the caterpillars then die a horrible-to-witness death.

tomato hornworm
This tomato hornworm parasitized by a tachinid fly or a type
of parasitic wasp doesn’t have long to live

There are people in these groups discussing the best way to eradicate tachinid flies from their garden, from catching and killing every one of them (good luck!) to placing fly strips close to their milkweed. Thankfully, most don’t advocate sprays as they know that’ll kill the caterpillars too.

I’ll admit I’m not thrilled when I find a monarch caterpillar parasitized by tachinid flies. It’s gruesome and seems cruel and I hate witnessing it. BUT, I also don’t do what the groups have suggested, which is to kill the tachinid larvae. They have a place in the garden, we’re not overrun with them, so I won’t mess with them.

According to this Mother Earth News article, tachinid flies prey on cabbage worms, tomato hornworms, Japanese beetles, army worms, gypsy moth caterpillars, cutworms, sawflies, codling moths, peach twig borers, pink bollworms, squash bugs, leaf rollers, and tent caterpillars.

Now, I don’t know about you, but I would much rather lose a few monarchs to tachinids than be overrun by tomato hornworms, cabbage worms, or squash bugs in my vegetable garden!

Several years back, this area of the country was plagued by an overabundance of gypsy moth caterpillars. They were everywhere. You couldn’t walk in the woods without being showered in caterpillar poop (yes, gross!), and they defoliated and ultimately killed thousands of trees. They were finally wiped out by a bacteria and a separate virus that typically gets them once their numbers get high enough.

And that brings me to my second point.

“Bad bug” numbers must be high enough for the good guys to show up

aphids on milkweed
Those dang yellow aphids on my milkweed!
I don’t like them, but I tolerate them

Just as with viruses and bacteria that need a certain critical population before they’re able to do their jobs, when you have just a few “bad bugs”, the good guys won’t bother showing up because there isn’t enough of a population to support them.

For instance, if I have a few aphids on my milkweed, I may see an occasional ladybug or lacewing, but there won’t be very many. Let the aphids start to proliferate and suddenly, ladybugs and lacewings proliferate too. You must have a certain level of pest bugs in your garden in order to support the good bugs you would typically welcome.

I’m not necessarily saying you shouldn’t attempt any kind of pest control at all, we’ll get to that in a minute or two. Bear with me.

The “bad guys” aren’t always just bugs

You know that birds eat caterpillars, right? They eat A LOT of caterpillars, especially when they’re raising their young and they need the extra protein.

Now, monarch caterpillars do have some protection in that after they’ve eaten milkweed for awhile, they become poisonous, but the younger caterpillars aren’t necessarily poisonous enough to keep birds from eating them in the beginning. There’s also some evidence that certain critters have adapted over time to deal with the poison.

flying bluebird
Male Eastern Bluebird

So, are you going to eradicate birds from your garden? I hope not! Besides being pretty and fun to watch, birds eat a dizzying array of crawling and flying insects. Want to see just how many types of insects birds eat? Check out this article. I imagine you’ll be as shocked as I was, I had no idea just how many it was!

The Bad Guys aren’t always the Bad Guys

Huh? Bear with me here. We just talked about birds, mantids and dragonflies being both bad guys and good guys. There are others as well.

I don’t think any gardener would argue against spiders being a beneficial insect in the garden, no matter how creepy they are to some of us *raises hand sheepishly*.

But, spiders are a major predator of caterpillars, often hiding right on the host plant and eating the caterpillar when it first hatches from its egg.

Have you read my other post on Beneficial Insects in the Garden? You might want to check it out as I talk about some of these critters there too!

The Good Guys aren’t always the Good Guys Either!

I know, I know, here we go again. But really, think about what monarch and swallowtail caterpillars do. They eat. And eat. And eat. Then they poop, they grow, and they eat some more.

Until you’ve raised them, you may not realize just how much these guys can eat, but Eric Carle and his “Very Hungry Caterpillar” were not off the mark.

eastern black swallowtail cat
Eastern Black Swallowtail caterpillar munching down on my dill

If you’re trying to grow parsley, fennel or dill for human consumption, Eastern Black Swallowtail caterpillars may very well become the bane of your existence. Mine ate ALL of my dill this year. Every. last. bite. I managed to salvage just enough for a couple of jars of pickles, but if I want to make more, I’m going to have to buy it!

Do I mind? No, they’re beautiful and I want to encourage and protect them, but they eat A LOT!

Just as in “regular” life, garden life isn’t always black and white. There are lots of shades of gray. Maybe not 50, but….sorry, I had to.

Some Pest Management may be Necessary

The other group I’m in won’t allow any talk of pest management at all, touting itself as a “no-kill” group. Any talk of pest control is met with immediate expulsion from the group.

To my way of thinking, this approach doesn’t work either.

For instance, squash bugs. In my experience, good bug numbers just don’t build fast enough in the spring to completely control squash bugs, and if you’ve had the obnoxious creatures in your garden, you know how quickly one or two can become 10,000 and ruin your crop.

squash bug
Squash bug

Because I want to end up with some cucumbers and zucchini from my garden, I do kill as many squash bugs as I can. Ditto for potato bugs, because my predator species just can’t keep up enough that I’ll have a harvest at the end of the summer.

I can’t believe that anyone in their right mind would advocate leaving a wasp nest next to your front door, or possibly even close to your milkweed patch (wasps are major predators of monarchs). There are certain times when the pests just need to go.

As far as the aphids on my milkweed go, though, I leave them alone as long as I can to encourage lacewings and ladybugs.

BUT, that said, if the milkweed I need for my monarchs starts looking ridiculously sick, I’ll first take the step of being sure the plants are well-watered and fed, because healthy plants fight insect attacks better than sick ones. If that doesn’t work, I’ll take some measures against the aphids, although I never try to get rid of every single one.

Another milkweed pest we have here is the tussock moth caterpillar. A good-sized group of these crazy-looking little buggers can defoliate milkweed plants in short order. But, there are other ways to control them that don’t involve killing or eradicating them.

tussock moth caterpillars
A whole passel of tussock moth caterpillars on my butterfly weed~
these guys always give me the giggles because they’re so funny-looking!

Tussock moth caterpillars love butterfly weed (Asclepias tuberosa) as much as milkweed varieties like common or swamp milkweed, so if they get on my milkweed, I’ll move them over to the butterfly weed. I have a lot more butterfly weed than milkweed, so figure it’s a good swap.

And that brings up another point: If you have pest bugs bothering your plants, can you plant more of a particular variety in a different location? Either the bugs will move to the new location and leave your original plants alone, or you may get away with no bugs in the new location as they’ll stick to their original area. Either way, you’ll hopefully have enough of the plant at that point to be able to peacefully coexist with the pest.

You may also find that planting a different variety of the same plant will help. I have common, swamp and showy milkweed in my garden. The aphids go after the swamp milkweed first, then will move on to the showy if numbers get high enough. They really haven’t bothered my common milkweed at all yet. So, can you live with some losses if you end up with some wins? If so, you’re good to go!

What’s a Gardener to Do?

You might be like me and want to protect your swallowtail, monarch or other caterpillars or butterflies.

Honestly, I’ve found the best solution is gathering the caterpillars (or even the eggs) before the predators can get to them, and raising them indoors where they’re safe. Of course, I can’t protect the butterflies once I release them, but figure since I release more than would survive in the wild, I’m still giving them a better chance for bigger numbers than if they were outside their whole lives.

male black swallowtail
A beautiful male black swallowtail in my garden

Maybe indoor raising isn’t possible for you. I get it, it’s a lot of time and work. If you want to know more about it, you can read my Raising Monarchs post here.

When you’re growing veggies, your best bet for insect control is crop rotation, as well as some of the tips below, which apply equally to veggies and flowers. Stay tuned in the coming weeks as I’ll be discussing crop rotation schemes in greater detail.

Planting lots and lots of different plants, particularly if they’re native to your area, is one of the best ways to protect the biological diversity in your garden. And as we talked about above, planting different varieties may give you some and the pests some, making it a win-win.

Plant a mixture of high and low-growing plants and some ground covers. This will give bugs the habitats they need to thrive. If you can, leave some ground bare. It doesn’t have to be a lot, but there are many ground nesting bees that need bare ground to burrow into.

Conversely, make sure you have some areas with deep mulch, as some other types of bugs need cover.

Besides flowers, do you have trees and bushes of different heights? These will encourage birds, giving them cover and nesting areas.

hummingbird and sunflower

You can, of course, feed the birds, including hummingbirds, which are such fun! As I typed this, I watched a hummingbird get ticked off at a goldfinch that must have been in his territory. That little tiny bugger just chased the much bigger goldfinch right across the yard! It was hilarious!

Water in the form of small ponds and upright plants will attract dragonflies (want to know more about attracting these fun and entertaining insects? Check out my post here). Water will also attract birds, and I’ve found that shallow water sources during hot summers even seem to keep the wasps and hornets happier, keeping them from getting as aggressive towards humans.

I hope my rant has been fun and informative for you. You don’t have to agree with me, because what fun would it be if we all agreed all the time?, but I hope I’ve given you food for thought on this issue. I’d love to hear your thoughts in the form of comments or questions.

If you feel so inclined, you’ll find some pinnable images below so you can pin for future reference.

Otherwise, smile and have a crazy organic day!

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biological diversity pin 1
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Why You May Want the “Bad Guys” in your Garden

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Sarita 09/09/2019 - 7:15 am

Okay, I’m fascinated, repulsed, and impressed all at the same time. What an interesting article, creepy-looking bugs and crawlies, and absolutely gorgeous photography. I’m going to show my kids, they’ll love the caterpillars, lol, and I’m sure they’ll go searching through our garden for some creepy crawlies of our own now, lol.

Dawn 09/12/2019 - 6:01 pm

Hahahaha, kids love creepy crawlies! Actually, I guess I’m still a kid because (with the exception of spiders) I love creepy crawlies too!

Nikki Gwin 09/08/2019 - 11:23 am

Excellent article!! Sharing.
🙂 gwingal

Dawn 09/12/2019 - 6:00 pm

Thank you!

Brenda Jones-Schneeberg 09/03/2019 - 10:51 am

I heard the tussocks can be moved to dogbane. Since butterfly weed is also a milkweed you might want to save it for Monarchs. Does dogbane grow in our area and where can I get it?

Dawn 09/03/2019 - 1:50 pm

It can be ordered from Prairie Moon Nursery. I’m not sure where to get it locally. I just figure since the butterfly weed is less preferred than other milkweeds, I’ll let the tussocks have it! LOL. Do please keep in mind that dogbane is quite poisonous to humans, if you do decide to grow it.


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