Caterpillars, as every schoolchild knows, eventually turn into butterflies and moths. So why do you want to get rid of them? They may be beautiful and excellent pollinators, but as caterpillars or larvae, unfortunately, they are one of the most destructive pests in vegetable gardens and orchards. Read on for advice on identifying signs of caterpillar infestations and how to control and get rid of them using non-toxic methods.
Signs of Caterpillar Activity
One of the most disheartening sights in the vegetable garden is your otherwise flourishing plants full of holes, or the leaves chewed down to their stems. Caterpillars can do a lot of damage in a short time. They tend to be most active in late summer and early autumn, right when many garden crops are starting to get bigger. While some caterpillars are showy or distinctive and easy to recognize, others have very effective camouflage and are challenging to spot. But there are signs of their presence.
- Eggs: These are left behind on the host plant by the butterfly. They may be hard to differentiate from other insect eggs, so be observant when you see butterflies lingering on your plants.
- Leaf damage: Caterpillars usually chew on leaves from the outer edges instead of leaving holes in the middle of leaves.
- Frass: Frass is the technical term for caterpillar poop. It looks like tiny grains of black pepper, and caterpillars tend to leave it behind wherever they are actively feeding.
- Webbed nests: Webworms and tent caterpillars' larval webbed nests and intense eating frenzies defoliates trees
How to Get Rid of Caterpillars
Many chemical preparations kill garden pests, but most vegetable gardeners agree that using such products around edible produce is not a good idea. Instead, try non-chemical and non-toxic ways to control caterpillars.
Remove By Hand
Hand removal is the most effective and straightforward way to remove caterpillars quickly. If they're not the nuisance kind, put on some well-fitting gloves and try relocating them, as caterpillars don't like to travel far from their birthplace in search of food. Put them in a cardboard box and bring them to a meadow or roadside area with plants. Don't put them in someone else's garden.
Children might be helpful with this task since many kids enjoy observing bugs. Perhaps you can create a small butterfly garden where the caterpillars will be encouraged to return.
If these caterpillars are pests destroying your plants, drop them into a bucket of soapy water to get rid of them.
Spray Neem Oil
Neem oil sprays kill small insect pests, like caterpillars and mites, by suffocation. It is a botanical extract made from the oil of Neem tree seeds. Neem oil is safe and will not harm humans or pets. It mainly affects caterpillars by stunting the insect's ability to mature. These sprays are sold commercially; follow the instructions marked on the packaging.
Use Bacillus Thuringiensis
Bacillus thuringiensis (Bt), a bacteria added to the spray formula, is one substance used to control caterpillars. It is toxic to some insects but not birds, fish, or mammals. If you want to go this route, ensure the formulation you get is not harmful to bees.
Remove the Nest
Two caterpillars make nests—webworms and tent caterpillars. Both are destructive to plants and trees. To reduce the damage from these caterpillars, discard these nests by hand before the larvae feed. You can also prune the trees to eliminate the nest, incinerate them, or leave them for natural predators like birds and wasps.
- Pepper spray: You can kill caterpillars with fresh peppers. Wear gloves and eye protection and finely chop enough habanero peppers to fill 1/2 cup. Crush six garlic cloves. Puree the peppers and garlic with 2 cups of water, 1 tablespoon of vegetable oil, and 1 teaspoon of dish soap in the blender. Pour the mixture into a quart glass jar and cap it tightly. Set it in direct sun for two days. Strain the pepper solution through a coffee filter into a spray bottle. Spray caterpillars generously.
- Molasses and dish soap: Mix a tablespoon of molasses and a teaspoon of dish soap with a liter of warm water. Once room temperature, spray the mix regularly over the leaves, top to bottom.
- Oil spray: This stripped-down version of pepper spray is ready faster and with fewer ingredients; combine 2 tablespoons of canola oil (or any vegetable oil), 1 teaspoon of dish soap, and 2 cups of warm water. Funnel the solution into a spray bottle and spritz caterpillars liberally. Don't use this on orchids, squashes, or hairy-leafed plants.
- Vinegar spray: A vinegar and water solution will kill and repel most garden pests, including caterpillars. Mix two tablespoons of vinegar with 1 gallon of water, and spray wherever you've seen caterpillars.
Causes of Caterpillar Infestations
You end up with caterpillars mainly because butterflies lay their eggs on or near your plants. Like many valuable species in nature, butterfly instincts help them locate the safest spot conducive to reproduction. They plan to make sure their offspring have plenty to eat to populate their species.
There are several effective ways to prevent caterpillars in your vegetable garden. Always do some research before purchasing any commercial preparation; sometimes, a product will say it's "safe" on the label when it's harmful in many ways. You shouldn't need to use harmful chemicals to control caterpillars; such products may harm pollinators, birds, or wildlife or leave toxic residue in your soil.
Moths are attracted to light at night, so if possible, try not to have lights around your garden at night; this will cut way back on moth traffic. If they're not around, they won't lay eggs.
Plant Food Crops and Flowers Separately
Butterflies are most attracted to nectar-rich flowers. If caterpillars are a problem, keeping your pollinator plantings separate from your food plantings will lessen the chance of a caterpillar infestation in your vegetable garden.
Some strong-smelling herbs, including lavender, sage, peppermint, and mugwort, will deter caterpillars. Don't plant mint directly in your garden, as it's very invasive, but placing a small container nearby may help keep caterpillars away.
As we've established, insects are intelligent, or at least, they're good at surviving. Switching out your crop varieties and locations of plantings from year to year makes it harder for butterflies and moths to establish themselves in your garden.
Protection of Crops
You can protect your tender young plants from caterpillars by using protective materials. Some gardeners successfully put cardboard or tin foil around the base of plants to repel caterpillars, who find these surfaces awkward to crawl over.
You can also use porous netting to protect your plants from caterpillars, but if the eggs were laid directly on your plants, this method might have limited success.
Attract Birds That Eat Caterpillars
A number of common backyard birds eat caterpillars or feed them to their young. These include American robins, yellow warblers, Carolina wrens, chickadees, sparrows, woodpeckers, and red-eyed vireos. Chickadees, in particular, prefer caterpillars for feeding their chicks. Creating a hospitable environment for these birds might help reduce your caterpillar problem.
Spray a Caterpillar Deterrent
Australian gardeners swear by using the horticultural molasses (available at garden supply centers) and dish soap method as a way to get rid of caterpillars. As a bonus, it also deters fire ants.
Caterpillars in Your Yard and Garden. University of Missouri Extension.