Caterpillars can be pesky garden pests, munching their way through prized flowers, vegetables, and other plants. While chemical pesticides are effective at controlling caterpillar populations, many gardeners prefer to try natural, non-toxic methods first. With some persistence and patience, it is often possible to get rid of caterpillars without resorting to harsh chemicals. This comprehensive guide covers a variety of natural, eco-friendly ways to control caterpillars in your yard and garden.

Remove Caterpillar Food Sources

One of the best ways to discourage caterpillars is to eliminate their food sources. Caterpillars feed on plant leaves, so reducing the amount of vulnerable plants can help reduce their numbers. Here are some tips:

• Remove host plants – Determine which plants caterpillars are feeding on and consider removing them entirely if they are not valuable to your landscape. This instantly takes away food sources.
• Clean up fallen leaves/debris – Caterpillars will feed on any leaves they can access, including fallen leaves on the ground. Rake up debris frequently.
• Clean garden thoroughly in fall – Many caterpillars overwinter as pupae in plant debris or the soil. Clear gardens completely in autumn to remove hiding spots.
• Use row covers – Cover susceptible plants with floating row covers or mesh to create a physical barrier against caterpillars.
• Plant less favored plants – Some plants, like onions, garlic, and mint, are naturally less appealing to caterpillars. Focus on these over favored plants like cabbage.

By limiting their food options, you can force caterpillars to go elsewhere to find their next meal. This approach requires diligence to continually clean up debris and monitor for damage, but can be effective season after season.

Use Natural Predators

One of the easiest biological ways to control caterpillars is to introduce natural predators into your yard. Many beneficial insects and other creatures like to feast on juicy caterpillars. Attracting these predators can create a natural system of checks and balances:

Birds

Birds like chickadees, nuthatches, and flycatchers all consume caterpillars. Attract them with:

• Bird feeders and baths
• Bird houses
• Berry producing plants
• Native plants and trees

Wasps, Hornets, Yellowjackets

Many common wasps are parasitic, laying their eggs inside live caterpillars. The larvae then devour the caterpillar. Avoid disturbing wasp nests near gardens.

Spiders

Web-building spiders catch and eat caterpillars and other insects. Provide habitat for spiders by leaving dead plant stems and allowing leaf litter to accumulate.

Ants

Ants patrol plants searching for caterpillars and other protein sources. They also farm aphids which produce a sugary waste, so having some aphids around can help keep ants hunting for caterpillars.

Ground Beetles

Large ground beetles live in leaf litter and patrol for caterpillars that fall from plants or attempt to pupate in the soil. Avoid applying thick mulch, which impedes movement.

With a bit of patience, these natural predators can take over caterpillar patrol and control them without any effort on your part! Periodic scouting of plants is still important though to assess if additional control is needed.

Use Physical Barriers

There are several effective physical barriers that can be implemented in yards and gardens to prevent caterpillars from ever reaching plants:

Row Covers/Mesh

Lightweight spun fabrics can be draped directly over plants, creating a tent-like enclosure. The fine mesh allows light, air, and water through but blocks insects. Anchor edges with stones, boards, or garden staples.

Aluminum Foil

Strips of aluminum foil wrapped around plant stems or branches create a slippery barrier caterpillars cannot traverse. The reflective surface also deters them.

Tanglefoot

This extremely sticky substance can be applied in bands around stems. Caterpillars get stuck in the goo if they try to cross.

Diatomaceous Earth

This powdery natural substance is abrasive to soft insect bodies. Dust it around the base of plants to irritate and deter caterpillars.

Copper Tape

Special copper tape wrapped around planters or tree trunks gives caterpillars an electric shock if they try to cross, repelling them.

Used proactively, these simple physical barriers can prevent caterpillar damage without harming any insects. They do require diligent monitoring and reapplication, but can be useful supplements to other organic methods.

Employ Natural Insecticides

When caterpillar populations grow out of control, gardeners may resort to using natural insecticidal sprays derived from plants. These can be effective alternatives to synthetic chemical pesticides:

Bacillus thuringiensis (Bt)

This microbial insecticide is derived from a naturally occurring bacteria that is toxic to caterpillars when ingested, but safe for humans. Different strains target specific species. It must be reapplied frequently.

Neem Oil

Pressed from neem tree seeds, this oil coats leaves with a bitter taste to deter feeding. It also contains azadirachtin which disturbs caterpillar growth and reproduction. Use a dilute solution to avoid plant damage.

Pyrethrins

Pyrethrins are botanical insecticides made from chrysanthemum flowers. They act as neurotoxins to quickly paralyze and kill caterpillars. However, they also kill beneficial insects and decay rapidly.

Insecticidal Soap

Soap-based insecticides dissolve the fatty outer layer of caterpillar skin, causing dehydration. Use potassium salts of fatty acids for best results. Can also deter feeding.

Spinosad

This biological insecticide comes from a natural soil bacteria. When ingested it affects caterpillar nervous systems. It must be applied early for best control.

While these have natural origins, insecticides can have unintended effects in ecosystems and should be used judiciously and precisely. Always follow label directions for correct preparation and application.

Disrupt Caterpillar Life Cycles

Instead of trying to kill active caterpillars, another approach is interfering with their life cycles:

Hand Pick Larvae

Carefully pluck any caterpillars found on plants and drop them into soapy water or alcohol to kill them. Check under leaves for hiding caterpillars. Be thorough and persistent.

Solarize Soil

Heating moist soil by covering it with plastic kills overwintering pupae and prevents future generations. Do for several weeks during hot seasons.

Apply Nematodes

These microscopic worms seek out caterpillar larvae in soil and infect them with lethal bacteria. Effective but can be expensive. Water soil first.

Trap Adults

Set pheromone or blacklight traps to capture adult moths before they can lay more eggs. Caterpillar numbers will decline over time.

Disrupting the caterpillar life cycle requires advanced planning and diligent effort but can lead to long-term reductions in infestations year after year.

Use Caterpillar Predator Urine

One novel biological control method for deterring caterpillars is applying predator urine in gardens. The scent frightens caterpillars away with the threat of imminent danger:

Fox & Coyote Urine

Apply these predator urines around vulnerable plants. The smell mimics caterpillar predators being nearby. Works for weeks.

Bobcat Urine

Bobcat urine has shown effectiveness at repelling caterpillars when sprayed or sprinkled around plants as a repellent.

Mountain Lion Urine

Products containing mountain lion urine are also available. The threatening scent scares many insects away from treated areas.

Repeat Applications

Reapply every 2-3 weeks to maintain the frightening scent. Rainfall dilutes urine so reapply after storms.

Predator urine is easy-to-find and simple to apply. However, some users report mixed results, with caterpillar damage continuing despite applications. Using multiple deterrent methods together may be more effective.

Use Caterpillar Repellent Plants

Certain plants have natural chemical defenses that repel or deter caterpillar feeding. Incorporating these plants into gardens can discourage caterpillar damage nearby:

Tansy

The strong aroma and bitter taste of tansy drives away many insects, including cabbage worms. Plant it as a companion to brassicas.

Mint

Mint contains caterpillar-repelling essential oils like menthol. It also attracts beneficial wasps. Plant it around susceptible plants.

Garlic & Onions

Related plants like garlic, onions, leeks and chives emit sulfur compounds that deter caterpillars. Interplant with them.

Marigolds

Marigolds exude an insect repelling chemical from their roots when planted among other plants. Also plant near cabbage family crops.

Catnip & Rue

Both the mint family herbs catnip and rue have been shown to repel certain caterpillar species when grown among other plants.

Interplanting these natural repellents with plants susceptible to caterpillar damage is an easy way to discourage them from feeding on choice vegetation.

Use Caterpillar Traps

Traps are another physical control method that can capture caterpillars en masse to reduce damage:

Pheromone traps

Traps baited with female sex pheromones lure male moths, preventing breeding and reducing future caterpillar populations.

Sticky traps

Yellow and blue sticky traps placed near plants attract and capture many small caterpillars before they can cause substantial damage.

Bacillus thuringiensis traps

Add Bt powder to bran flour bait stations to attract caterpillars which then consume the bacteria and die.

Duct tape

Wrapping sticky duct tape around plants stems traps small caterpillars attempting to climb plants and feeds on leaves.

Jar traps

Poke holes in old jars and hang near plants as caterpillar traps. Caterpillars crawl in but cannot get back out.

Check traps frequently to dispose of any caught caterpillars or moths. Traps alone may not eliminate infestations but help reduce their severity.

Make Caterpillar Habitat Unappealing

Caterpillars tend to congregate and cause more severe damage if conditions allow. Making plants and their surrounding habitat less hospitable can deter serious infestations:

Reduce nitrogen fertilization

Caterpillars prefer the fast lush growth caused by high nitrogen. Use less nitrogen fertilizer to slow plant growth.

Avoid excessive watering

Overly moist soil and wet leaves create better conditions for caterpillar outbreaks. Allow soil to dry between waterings.

Manage weeds

Weeds provide additional caterpillar food sources. Keep gardens weeded to remove extra habitat.

Increase air circulation

Good air movement through plants disrupts caterpillar movement and feeding. Space plants appropriately.

Keep garden clean

Caterpillars hide and feed under debris. Remove fallen leaves and other litter frequently.

With some adjustments, you can make life more difficult for caterpillars. Combined with other deterrents, these steps help throw off their dining schedule.

Use Caterpillar Parasitic Nematodes

An innovative biological control method for caterpillars is applying parasitic nematodes. These microscopic worms naturally infect caterpillars and kill them:

Heterorhabditis bacteriophora

This nematode species targets over 250 caterpillar species. Once inside, symbiotic bacteria kill hosts within 48 hours.

Steinernema feltiae

Proven effective against many common caterpillar pests. Kills hosts within 24 hours of infection. Survives well in soil.

Apply at night

Parasitic nematodes are sensitive to sunlight and spread best at night. Thoroughly water soil first.

Reapply every 2-3 weeks

For heavy infestations, repeat applications are needed. Nematodes have short life spans.

Works best on soil dwellers

Parasitic nematodes work well on caterpillars in soil like cutworms. Not as effective on foliage feeders.

While entomopathogenic nematodes show promise, their short shelf life means culturing your own nematodes may be necessary for best effect. If purchasing, confirm viability upon delivery.

Use Caterpillar Killing Fungi

Specialized strains of entomopathogenic fungi can also provide natural caterpillar control. These fungi infect and kill specific caterpillars and related insects:

Beauveria bassiana

This fungi causes white muscardine disease in caterpillars, eventually killing them as mycelium covers their bodies.

Metarhizium anisopliae

Infects caterpillar bodies, causing death within 3-7 days. Helpful for soil-dwelling caterpillars.

Isaria fumosorosea

A strain with proven effectiveness against certain caterpillar species and other insect pests. Causes mortality within 3-7 days once ingested.

Apply dusts liberally

Fungal spores work best in dry form directly dusted onto caterpillars. Reapply after rain.

Spray young larvae

Early instar caterpillars are most vulnerable. Target them before extensive feeding damage occurs.

Combine with other methods

These fungi alone rarely eliminate full infestations. Use alongside other organic controls.

Field results are somewhat mixed, but entomopathogenic fungi remain a promising eco-friendly tool in the battle against caterpillars. With improved strains and application methods, they may prove even more effective in the future.

Import Caterpillar Killing Wasps

Introducing parasitic wasps is an intriguing biological control method. Certain wasp species lays their eggs inside living caterpillars, providing a potent natural weapon:

Cotesia glomerata

This common parasitic wasp devastates many white cabbage butterfly larvae when present. The wasp larvae devour their caterpillar host.

Cotesia rubecula

A specialist on imported cabbageworms. Each wasp larva can consume up to 60 caterpillars before emerging to pupate.

Trichogramma brassicae

These tiny wasps parasitize eggs of destructive moths like cabbage loopers, preventing caterpillars from ever hatching.

Ensure proper identification

Only introduce known parasitic species, not generalist wasps. Consult an expert entomologist.

Time releases carefully

Parasitic wasps must be present during host caterpillar stages to be effective. Scout for pests first.

Combine with other controls

While impactful, imported wasps alone rarely provide complete control. Use alongside other methods.

Releasing biological controls like parasitic wasps carries some risk and should only be attempted by trained professionals. When successful, they can provide ongoing caterpillar control. But results are unpredictable under variable field conditions. Proceed with caution.

Apply Caterpillar Killing Bacteria

Several bacteria naturally found in soils have insecticidal effects on caterpillars when ingested or exposed. Commercial products containing these bacteria can provide biological control:

Bacillus thuringiensis (Bt)

This common caterpillar killing bacteria paralyzes digestive tracts on ingestion, causing death. Must be reapplied frequently.

Bacillus popilliae

Causes lethal blood infections in Japanese beetle larvae. Also shows effectiveness against related white grub species.

Serratia entomophila

Colonizes the bodies of certain soil-dwelling caterpillars like cutworms, causing mortality within days. Causes amber disease.

Spinosad

A bacterial byproduct toxic to caterpillars. Causes twitching, paralysis, and death within 1-2 days of application.

Follow label rates carefully

Only apply recommended amounts to avoid plant damage. Do not overapply.

Target early instars

Bacteria work best on young, actively feeding caterpillars. Older larvae can resist infection.

Combine treatments

These bacteria alone may not fully control heavy infestations. Incorporate into a multifaceted program.

With the right strains and applications, bacteria can provide selective, natural caterpillar control without negative environmental impact. They are valued additions to any integrated pest management program.

Handpick and Squish Caterpillars

Sometimes the simplest control methods are most effective. Diligently handpicking caterpillars and squishing them can eliminate infestations:

Scout plants thoroughly

Inspect plants often, checking undersides of leaves for caterpillars missed by other methods.

Remove egg masses

Scrape off any caterpillar egg masses found on leaves or stems before they can hatch.

Drop in soapy water

Collect caterpillars in jars or buckets filled with soapy water to quickly kill them.

Squash larger species

Simply squish larger caterpillars in place on plants using gloved hands or pliers.

Persistence is key

Handpicking requires patience and vigilance, but can control isolated infestations.

Even with other organic controls in place, handpicking can help eliminate the last remaining caterpillar holdouts. Satisfaction guaranteed! Just remember to wear gloves.

Frequently Asked Questions about Controlling Caterpillars Naturally

Controlling caterpillars using non-toxic methods requires an integrated approach. Here are answers to some commonly asked questions about managing these leaf-munching pests organically:

What is the most effective natural way to control caterpillars?

There is no single magic method for caterpillar control. The most effective approach is to employ multiple organic tactics like using parasitic wasps, applying Bacillus thuringiensis, handpicking, and disrupting their life cycle. Pest management requires diligence and persistence to achieve success.

How do you get rid of cabbage worm caterpillars naturally?

For common cabbage worms, use row covers