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Writer's pictureAndy Hemmer

Diatomaceous Earth for Cabbage Worms

Updated: 5 days ago


cabbage worm

Cabbage worms are a bane for gardeners growing cruciferous vegetables such as cabbage, broccoli, kale, and cauliflower. These voracious pests can quickly damage crops, leaving frustrated growers in their wake. However, there’s an effective, eco-friendly, and affordable solution to this common problem: diatomaceous earth (DE).


In this blog post, we’ll explore how diatomaceous earth can be used to kill cabbage worms brought forth by adult butterflies, the worm laid by diamondback moths, and cabbage loopers, cabbage looper trichoplusia ni and protect your garden without resorting to chemical pesticides.



 


What Are Cabbage Worms?

cabbage worm destroying cabbage plant

Cabbage worms are the larvae of the small white butterfly (Pieris rapae), also known as the cabbage white butterfly. These green, velvety caterpillars are infamous for their ability to blend in with the foliage of cruciferous vegetables, making them difficult to spot.


Signs of Cabbage Worm Infestation


  • Holes in Leaves: Chewed leaves are the most obvious sign.


  • Black Droppings: Cabbage worms leave small, black fecal matter on plants.


  • Damaged Heads: In severe infestations, the worms can burrow into cabbage heads, ruining the crop.



 


What Is Diatomaceous Earth and How Does It Work?

diatomaceous earth

Diatomaceous earth is a fine, powdery substance made from fossilized diatoms, a type of algae. It is primarily composed of silica and has sharp, microscopic edges that are lethal to pests but harmless to humans, pets, and beneficial insects when applied correctly.


When cabbage worms come into contact with DE:


  1. The sharp particles scratch their exoskeletons.


  2. This causes them to lose moisture and dehydrate.


  3. Eventually, the worms die from desiccation.


Unlike chemical pesticides, DE works mechanically rather than chemically, making it safe for organic gardening. This is your ultimate organic alternative for eliminating the life cycle of these insects.



 


How to Use Diatomaceous Earth Against Cabbage Worms

start of a cabbage worm infestation

Step 1: Choosing DE for Your Garden

Ensure you’re using diatomaceous earth that is garden-safe and can get rid of cabbage worms, as it’s safe for use around edible plants. Avoid pool-grade or filter-grade DE, which is processed differently and not safe for gardening or you.





Step 2: Apply DE to Affected Plants


  1. Timing Matters: Apply DE in the early morning or late afternoon when plants are dry, and there’s no wind. DE is less effective when wet for pest control.


  2. Dust the Plants: Use a duster or a fine sieve to sprinkle DE on the leaves, stems, and the soil around your plants. Pay special attention to the undersides of leaves, where cabbage worms often hide.


  3. Create a Barrier: Spread a layer of DE on the soil around your plants to deter crawling pests from reaching them.


Step 3: Reapply as Needed


  • Reapply after rain or watering, as water can wash away the DE.


  • Repeat the application every few days during an active infestation until the worms are under control.


Step 4: Monitor and Adjust

Regularly check your plants for signs of cabbage worms and reapply DE if needed. Combine DE with other pest management strategies for maximum effectiveness.



 


Benefits of Using Diatomaceous Earth for Cabbage Worms

healthy cabbage being harvested

  • Natural and Non-Toxic: Safe for humans, pets, and pollinators when applied properly. Safer than neem oil and bacillus thuringienis.


  • Cost-Effective: A single bag of DE can last for multiple applications.


  • Eco-Friendly: Unlike chemical pesticides, DE doesn’t harm the environment or leave harmful residues.


  • Versatile: Besides cabbage worms, DE works on other garden pests such as aphids, slugs, and beetles.



 


Tips for Preventing Cabbage Worm Infestations


While diatomaceous earth is highly effective, prevention is always better than cure. Here are some tips to minimize the risk of cabbage worms:


  1. Crop Rotation: Avoid planting cruciferous vegetables in the same spot every year to disrupt the pest lifecycle.


  2. Floating Row Covers: Use lightweight fabric covers to prevent cabbage white butterflies from laying eggs on your plants.


  3. Companion Planting: Grow strong-scented plants like dill, thyme, or mint nearby to deter pests.


  4. Handpicking: Regularly inspect plants and remove any visible worms or eggs by hand.


  5. Other Products: Using natural products like bacillus thuringiensis (BT) and neem oil in conjunction with diatomaceous earth gives you the upper hand on the cabbage looper (trichoplusia ni) or cabbage worm. You may also use soapy water and spray onto your cabbage to help prevent these insects.



 


Conclusion


Diatomaceous earth is a game-changer for gardeners dealing with cabbage worms. Its natural, mechanical action offers an effective and affordable way to protect your crops without resorting to harsh chemicals. By combining DE with preventive measures and good gardening practices, you can keep your garden healthy and thriving.


So, grab a bag of food-grade diatomaceous earth and take control of your garden the natural way. Your cabbages—and your wallet—will thank you!


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