Parsley worm is a small, ravenous garden beastie that likes to devour many different vegetable and herb crops. If you’ve had problems in the past with “something” eating your parsley, cilantro, or carrots, it was probably this guy.
In this article, we’re going to teach you how to identify it, how you can eliminate it, and hopefully fend it off in the future.
What You’ll Learn About Parsley Worm
What is a Parsley Worm?
Although it’s called a worm, the parsley worm (Papilio polyxenes) is actually the larva of the Black Swallowtail butterfly. These butterflies are wonderful, efficient pollinators for all manner of vegetable and fruit species, but their larvae are so voracious that they can wreak serious havoc on many different garden crops.
In its larval stage, parsley worm is also referred to as the “carrot caterpillar”, “celery stalker”, or “little green bastard”, as the case may be. These moniker refer to its preference for plants in the carrot family (Apiaceae or Umbelliferae), including:
How to Identify Them
Black swallowtail butterflies can be found all across North and South America, from southern Canada to southern Argentina.
When it comes to identifying them in their larval parsley worm form, look for pretty, bright green caterpillars that are around two inches (4.5 cm) long, with black horizontal stripes interrupted by yellow spots.
As they mature, they often develop short, dark, spiky “horns” sticking out from the black bands. They’ll likely be munching happily on your parsley, dill, celery, or carrot greens, thus giving themselves away.
Management Methods
It’s important to note that since Black Swallowtail butterflies are important native pollinators, it’s important to treat them gently rather than treating them like enemies to nuke from orbit. In an era where our pollinator species are dying off at a terrifying rate, finding ways to coexist with the parsley worm is the best course of action.
1. Row Covers
This is one of the best options you can go for to protect any vulnerable crops against butterfly or moth larvae.
We use row covers to keep cabbage white butterflies off our brassicas, but they’re just as effective at keeping parsley worm Swallowtails from laying their eggs on your parsley, dill, or carrots.
You can set up row covers quickly and easily by draping fine mesh fabric over low frames to protect your crops. You’ll need to either weigh or pin these down along the sides so they don’t blow off, or otherwise secure them to the frames they’re draped over.
These are available at any garden center or online. We even repurpose old mosquito nets as row covers sometimes!
2. Natural Insecticide
One of the best natural insecticides around is neem oil, and it’s been proven to be effective against parsley worm larvae. The larvae can’t stand the taste of neem, so they’ll crawl off to find food sources elsewhere.
Get yourself a bottle of cold-pressed neem oil, and create a spray with it using the instructions on the bottle. Then, hose your plants down with it regularly to deter the worms from munching them into oblivion.
3. Trap Crops
Since the pernicious parsley worm loves all members of the aforementioned carrot (Apiaceae) family, you can coax them away from your herbs and veggies by planting trap crops that you don’t really care about nearby.
For example, try planting barrier areas of fennel, Queen Anne’s lace, and angelica several feet away from your herb or carrot beds. The hope is that they’ll lay their eggs and hang out on these plants rather than your more important ones.
Think of this rather like distracting small children with a buffet of donuts and cookies so they stop caring about the fancy food that’s a bit further on. They do not need to look beyond what they’re being offered.
We often do this with previous years’ seeds as well. If we have carrot or parsnip seeds that are a few years old and no longer “fresh,” we’ll sow them on the periphery of our property.
On the off chance that they germinate, they can provide a distraction (and food) for these larvae, and the squirrels are welcome to dig up the roots when autumn and winter roll around.
4. Natural Predators
If you find that your garden is being overrun by parsley worm larvae, then you can try to encourage natural predators to help you reduce their numbers.
Unlike tastier caterpillar species that chickens and ducks like to feast upon, these caterpillars aren’t eaten by many birds. Apparently, this is because they taste quite foul, especially those that have eaten anise plants.
Most animals don’t like the taste of licorice/anise, and that goes for most bird species as well. That said, some species, such as chickadees, Baltimore orioles, barn swallows, and bluebirds, will eat them if other food is scarce. So will amphibians and reptiles such as frogs, snakes, and toads.
Parsley worm larvae are also vulnerable to parasitic braconid wasps and tachinid flies. Plant yarrow around the area to attract these wasps, and they’ll do their thing with the larvae to keep populations down.
5. Prevention
Parsley worm pupae overwinter in garden bracken and emerge as their beautiful butterfly selves once the weather warms up again.
Since these butterflies are vital indigenous pollinators, it’s best not to put detritus, such as fallen leaves and twigs, through a chipper or burn them. We don’t want to harm these creatures—we just don’t want them eating our parsley and carrots.
If you don’t want to risk having parsley worm larvae in your garden, aim to keep the ground as free from detritus as possible. In autumn, we rake up all the leaves and dead plants and dump all of that at the far end of our property, near the compost bins.
These are a couple of hundred feet from any of our grow beds. Should you choose to go this route, this is the ideal place to plant those trap crops we discussed earlier: the larvae will find those immediately upon emergence and won’t think to venture further for food.
As mentioned earlier, these are important native pollinators, so please try not to annihilate them. If you find that they’re severely damaging your plants, try to aim for natural deterrents and management methods rather than causing them real damage.
The world needs healthy pollinators now more than ever, so learning how to live harmoniously with these little weirdos is the best option for everyone.
