Jun 22, 2022

Garden Problems 101, Part 3: Caterpillars

As we continue our series on common garden problems, I would be remiss if I didn’t mention caterpillars.

These hungry little beasties suddenly appear, and eat their way through your plants like the Tasmanian Devil destroys things in old Looney Tunes shows. 

Let’s learn more about them and what you can do if you find yourself in a battle with these insects. 

What are caterpillars?

Caterpillars

Now, as many of you know, caterpillars are the larval form of moths and butterflies (for the most part), and as such, doing anything to the larvae is controversial in many circles.

Many people categorize caterpillars as “good ones” and “bad ones.” The “Good” caterpillars are usually the ones that are the larvae of desired butterflies, like Monarchs and Swallowtails.  The “Bad” caterpillars are often the ones that no one really ever sees the adults, like various moths that only come out at night.

Because of that, I’ll be covering a few different common worms/caterpillars that you find in Florida, and showing what moth or butterfly they belong to, so that you can make an educated decision on whether or not you want to share your plants with these critters or not.  I’ll also give you suggestions on pest control for these critters.

What are some common Caterpillars I might frequently see?

I’ve picked a few here that I see a lot of questions about on local gardening groups.  There are more, of course.  The internet is a wide and wonderful place with all kinds of identifying pictures.  Google Lens image search has really helped me many times!

Here’s some ones I thought you might like to see.

Monarch Caterpillar and Butterfly

Monarch Caterpillar and Butterfly

 

Hornworm and Sphinx Moth

Hornworm and Sphinx Moth

(colorings of the worms and moth species vary depending on the individual species!)

Swallowtail Caterpillar and Butterfly

Swallowtail Caterpillar and Butterfly

 

Black Cutworm (AKA Army Worm) and the moth adult

Do you have a favorite moth or butterfly?  Go look up what the worm looks like right now!  Here’s another article I found interesting – it lists other common Florida caterpillars! 

What does Caterpillar damage look like?

Cabbage worms / caterpillars on cabbage leaves

Caterpillar damage can look like many things, but for the most part, people notice when leaves have giant holes eaten in them!  There are other signs, too, and we’ll look at those below.

Caterpillar Poop!

Caterpillar poop!

Perhaps you’ve heard of, or read, the book “Everybody Poops”.  Well, it’s also true of Caterpillars!

Caterpillar poop is called “Frass” and often in my garden I spot the frass before I spot the critters themselves!  It’s usually because it looks so out of place where it lands – just a pile of “leaf colored” or brown/black “pebbles” that aren’t on the ground where you expect pebbles to be. 

Upon closer inspection they’re not pebbles at all.  When I inspect the underside of the leaves immediately above that spot, I’ll usually find some caterpillars munching away.  And they’re usually quite small which makes them hard to find!

Caterpillar Eggs

Caterpillar eggs

Well I guess they’re not technically damaging, because really they’re very hard to see, but the eggs that the caterpillars hatch from are the beginning of damage to come.

Evolution has dictated that the eggs are laid by adult insects onto a plant that will feed their young.  So if you see tiny dots of eggs on the bottom of the leaf, you can be assured that whatever comes out of them WILL eat that plant.

You just have to decide if that’s OK with you.

Different species lay different colored eggs, and often you can attribute different eggs to different types of lepidopterae (the family of butterflies and moths).  But you’ll need a magnifying glass; these eggs are TINY!

I Definitely Have Caterpillars. What Can I Do?

Caterpillar

Having caterpillars isn’t necessarily something you have to do anything about. Having said that, sometimes you may feel the need to save some plants from the hungry hordes!

For instance, those of you who grow milkweed for monarchs, you expect the caterpillars to eat the plants down to little nubs, and the milkweed plants will come back. 

But if you are growing prized heirloom tomatoes, and they get attacked by hornworms, you might want to save your plants so that your hard work raising tomatoes can bear fruit!

Let’s talk about some things you might want to try to help mitigate caterpillar damage.

Hand-picking

Caterpillar

One of the least invasive and safest methods of mitigating caterpillar damage is to physically remove the caterpillars from the plants you want to protect.

That means when you locate the caterpillars, you use your fingers to remove the caterpillar and place them elsewhere, such as in a bucket to feed your chickens or other worm-eating pets, or in a pail of soapy water, or just to move to a plant you don’t really care if they eat a few leaves.

Plant Extra

Plant Extra Plants for Caterpillar

Some people deal with caterpillars by just planting extra plants.  Only need 4 tomato plants to produce for you and your family? Plant 8. 

Then when you see caterpillars on certain plants, move them to the “extra plants” so that those little insects can grow up and fly away.

Organic Caterpillar Treatment

Treating Caterpillars

There are organic options to treat for caterpillars.  One is a biological insecticide that uses a specific microbe that targets caterpillars and interrupts their life cycle.

The product is called Thuricide B.T.  B.T. stands for “Bacillus Thuringiensis”, which is the biological additive to the product.  It comes as a concentrate, so you add it to a gallon sprayer and then add water (follow instructions for the proper ratio). 

Also, there’s a product called Dipel Dust that has the same ingredients but is not labeled organic.  It costs a lot of money to put a product through the OMRI process and many companies choose not to do it!

Treatment should occur on the tops and undersides of the leaves in the early morning or evening (it degrades in sunlight). Reapply at 5-7 day intervals, and/or reapply if there is a heavy rain.

Other organic options include:

Neem Oil – apply the same way as Thuricide, but keep in mind that neem oil kills all insects, not just caterpillars.

Diatomaceous Earth – this is a powder that you apply to the caterpillars and the leaf surfaces.  Note that DE doesn’t work when wet, it easily washes away in rain and irrigation, and harms other insects. 

Other Treatments

Treating for caterpillars

The old standby when I was a child was Sevin Dust, which now also comes in a liquid.  I remember that was what Daddy used in the garden when the bugs got too bad.  He always made sure that he waited the appropriate amount of time after treating to harvest, and washed the veggies really good afterwards too.

Sevin products use Carbaryl, a non-specific insecticide.  You can also buy it in the form of 5% Carbaryl dust.

There are all kinds of chemical treatments out there for worms/caterpillars, and we’re happy to help you find what works for you!

 

 

So, what do you think about caterpillars now? Was this information helpful?  Let me know what other common garden problems you would like me to write about.

Missed the first two installments of this series? Don’t worry. Here’s links: 

Aphids

Fungus

Until next time, Keep Growing!

Marissa

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