It may come off as strange given the kinds of plants I grow, but I’m not one for unnecessarily killing any creature – even insects. That said, I’ve had enough caterpillar pests to have firmly concluded that, within carnivorous plant collections, they are evil incarnate and must be dealt with without empathy or remorse.

Sarracenia (North American pitcher plants), in particular, are susceptible to caterpillars chewing both leaves and rhizomes. At best, you’ll end up with deformed, hole-laden pitchers. At worst, if left untreated, caterpillars can kill your plants.

I’ve had personal experience with a particularly sinister caterpillar, which I believe to be a cutworm. They’re the larval form of night-flying moths in the family Noctuidae and exhibit solitary feeding behavior, with only one or two found on a single plant. Don’t let their lack of numbers fool you – the little buggers will chew holes right into the rhizome of a Sarracenia, hollowing it out while killing new growth, and leaving it susceptible to infection and rot even if it survives the initial attack.

Caterpillar responsible for Sarracenia damage
A rhizome-boring caterpillar picked off of a Sarracenia

So, how do you identify caterpillars in your collection, and how do you take care of the problem?

Identify the signs of a caterpillar problem

While sometimes they hang out on leaves, caterpillars can be sneaky – hiding at or just below the surface of the soil, snuggled up in their next meal; your plant. You may have to ID a caterpillar infestation based on damage alone. Damage to your plant can occur in multiple forms. Holes chewed in leaves are an easy indicator. More sinister species like cutworms will bore into and eat the crown, or rhizome of your plant. Damage appears near the surface of the soil as hollowed out rhizome. Brownish-orange pellets (caterpillar waste) will frequently be found in small mounds next to the damage. Sometimes, you may even find a silky web where the worms are setting up a home on your plant.

Caterpillars confirmed. Must destroy. But how?

The quick-and-dirty pick-and-squish method is going to minimize short-term damage that the caterpillars will do to your plants. I recommend doing a manual sweep and getting as many removed as possible. However, I also recommend using a Bacillus thuringiensis pesticide to finish the job and introduce some longer-term garden resilience.

What is this fancy Latin word? Bacillus thuringiensis, or B.t., is the scientific name for a soil-dwelling bacteria that wrecks the digestive tract of caterpillars once ingested. Different strains of Bacillus attack specific garden pests (some attack mosquitos, for instance) with little overlap to other insects. It’s a naturally-occurring bacteria, is non-toxic to humans and pets, is non-polluting, and because it’s so selective with which insects it attacks, it doesn’t harm the beneficial insects and prey insects that visit your garden. It’s a solid caterpillar pesticide with very few, if any, downsides.

Bacillus thuringiensis caterpillar treatment

B.t. works after being ingested by the caterpillar. It grows in their digestive system and creates crystal toxins that bind to cells of the gut wall and kills them. It effectively stops caterpillar snacking within minutes of ingestion, and results in death 2-5 days later.

There are liquid Bacillus thuringiensis pesticides that can be diluted and added to spray bottles to apply to your plants. I use this “Safer” brand one from Amazon (affiliate link to help support the site) and put it through the same sprayer I use to foliar feed my other carnivorous plants. I give the leaves, rhizome, and surrounding soil a solid soaking, and B.t. handles the rest.

I hope this article helped you identify and treat caterpillar infestations in your carnivorous plant collections! Let’s continue the learning down in the comment section, below. Let me know – have you had caterpillar problems in your carnivorous plant garden? How was the damage? How did you handle it?

As always, happy growing!