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How to Identify and Control Caterpillars Naturally
- Jun 2
- 5 min read
It is the time of the year when our temperatures in North Florida are getting into the 80’s, while some family and friends in the north are still getting snow.
For those of you with temperatures rising up out of freezing, here come the bugs! For those of you still in freezing temps, the bugs will be coming soon enough, so this is for you too!
As the temperatures rise, this is the perfect time to address situations you may encounter with pests. I started to touch on this topic in the last blogpost; in the upcoming blogpost, I will go a little more in-depth.
I was going to start by discussing aphids because I have been seeing them on my plants for the last month. However, the caterpillars started showing up last week, already causing some real damage.
When Waiting One More Day Is Too Late
Have you ever planned to do some work in your garden, seen that you needed to address an issue and figure you will deal with it tomorrow? Something like harvest, or in my case, spray to control caterpillars? Then the next day comes and it’s already too late - what you were going to harvest is gone or damaged by those dang caterpillars!
This just happened to me - the morning I set out to spray for worms, I was one night too late.
Identifying the Real Problem
I have white lilies growing around the yard. In the last few years, they have had their tops taken right off (perhaps you’ve seen me talk about this on my social posts). Scouting for what caused the damage is always my first step.
The top was completely gone. There were no parts of it anywhere around the plant or on the ground. As I looked further, I noticed deer tracks. I determined this to be the culprit because they bite off the top and eat it, so I draped the tulle material over other lilies in the yard to deter this behavior, which seemed to do the trick.
Well, that was last year. Recently while scouting my yard, I noticed something wrong under the tulle material over the lily. After taking a good look, I found the problem. Ah, if I had just sprayed the day before… damn it! Caterpillars wrecked havoc on those lilies! The tulle took care of the deer problem, but did nothing to help with the caterpillars!
How to Identify Caterpillar Damage
If you suspect caterpillars, most of the time you are looking for holes in leaves. When the larvae are newly hatched, they cannot eat all the way through; what you will see is what looks like little windows in the leaf. As they continue to grow larger, they can eat through the leaf and also from the sides of the leaves to consume them easier.
Using Bt for Caterpillar Control
To help get rid of caterpillars, I use a product referred to as Bt (Bacillus thuringiensis).
I will try to give you an idea, in laymen’s terms, what Bt is and what it does.
Bt is a naturally occurring bacterium that acts as a biopesticide, which generally poses fewer risks compared to synthetic pesticides, by producing toxins that specifically target and kill certain insect larvae when ingested, so it’s killing it from the inside out.
When susceptible insects consume Bt, the toxins are activated in their highly alkaline digestive systems (pH 9.0 to 10.5). This is different from the acidic environment of the human gut, which renders Bt harmless to humans and other non-target organisms.
The activated toxins bind to the gut lining of the insect, creating holes and leading to the breakdown of the gut wall. This results in the insect's inability to digest food, causing starvation and ultimately death within a few days.
The label indicates that the pests stop eating right away which leads to the eventual death within days.
Bt is not toxic to non-target species, so it’s considered safe for humans, birds, fish, and beneficial insects, making it a preferred choice for organic pest control.
You need to apply Bt as soon as possible because it is most effective on the smaller caterpillars. When the caterpillars are larger, the application rate might need to be increased.
There are many strains of Bt that affect different pests. You may have heard of the mosquito dunks that are put in standing water to eliminate mosquito larvae. It’s a different strain of Bt that specifically targets mosquitos.
There are also several insecticides that will kill caterpillars, but even some of the organic options can be harmful. READ THE LABEL.
Some Caterpillars Sting
One word of caution: Some caterpillars can sting! They have tiny hair-like fibers that can be very painful. There are several different types, but the ones in the photos have been invading my yard each year. What look like spots along their back are clusters of these stinging fibers. Don’t touch them on purpose! I’ve had them drop out of the trees. The sting lasts for days.
Two years ago when I went out of town, this type of caterpillar ate and removed ALL of the leaves of my highbush blueberry. The next year no blueberries grew, only foliage.
Let’s Talk About Butterflies
If you love butterflies, you have another reason to learn what you are looking at so you aren’t killing the wrong thing.
In the last couple of years, I noticed that something was on the citrus. This small round solitary pearl shaped thing was on my citrus leaves. To me it was obviously an egg of something. But what?
I’ve learned to avoid killing anything I’m not sure about. This year I saw more of these little “pearls,” but this time I was able to see what hatched from it: A swallowtail butterfly larva!
Butterflies are beneficials because they are pollinators, so I want to keep them, plus they are beautiful to look at! I kept an eye on it and watched it develop into a caterpillar that looked like bird poop on the leaf. Next I will see the chrysalis (cocoon).
This is a very important reason for identifying various things in your yard. If I reacted right away I would have sprayed these plants, killing these beneficials, and that would have meant less swallowtail butterflies playing in my garden.
I’ve learned over the years you have to sacrifice some plants if you want butterflies. The larva do eat the leaves, but it’s worth it.
Creating a Butterfly-Friendly Garden
If you are a person trying to promote a butterfly garden, I suggest getting to know what the caterpillars of your butterflies look like and how to distinguish them from caterpillars that are pests.
If you're interested, I have some more photos of caterpillars you don't want and what butterfly eggs look like here.
Next, I'll talk about aphids! If you can't wait, you can check out my YouTube video where I talk about aphids and scale.
I also have this blog article about aphids, scale and whitefly.
If you have friends who are complaining about pests overtaking their garden, share the sign up link below so they can receive these newsletters and benefit from this information!
Here it is: https://heavenlyflower.ck.page/2147c195cf
If you have any questions, let me know. I'm happy to help!
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