Worm castings are incredible for our gardens due to their impressive nutrient content and ability to enhance soil health. But did you know that worm casts also help protect plants from pests?
The natural composition of worm castings (essentially worm poop creates a resilient environment that deters many common pests, offering gardeners an organic alternative to chemical pesticides. They also help suppress common diseases, keeping your plants in good health.
In this guide, we’ll explore how worm casts deter pests and suppress diseases, the specific pests and diseases they help control, and how you can use worm casts to strengthen your garden’s natural defences.
How worm casts work to deter pests
Worm casts contain beneficial microbes and enzymes that improve plant health and strengthen natural defences. As earthworms digest organic material, they produce an enzyme called chitinase, which breaks down chitin, a component found in the exoskeletons of many insects.
Chitinase can deter pests that feed on plant roots, leaves and stems. This is because when a pest eats a plant that has absorbed chitinase (via the worm castings), its stomach will dissolve and the pest will die.
Plus, the beneficial bacteria and fungi in worm casts promote strong root growth and improved nutrient absorption. Healthier plants tend to have a stronger resistance to pests, which makes them less likely to suffer from infestations. This natural resilience allows plants to withstand the impact of pests without the need for chemical interventions.
How worm casts suppress diseases
Worm castings naturally contain a range of microorganisms, including beneficial bacteria and fungi, which compete with and inhibit disease-causing pathogens. Additionally, the presence of humic substances in worm casts improves soil structure and moisture retention, which can make conditions less favourable for diseases to establish.
To keep your soil or compost topped up with these beneficial microbes, apply worm casts directly or dilute a handful in a watering can to use as ‘worm tea’. You’ll effectively crowd out harmful pathogens and promote a healthier, disease-resistant environment for your plants.
Diseases suppressed by worm casts
Worm casts can offer protection against several soil-borne and foliar diseases. The beneficial microbes, fungi and enzymes in worm castings create an environment where disease-causing pathogens struggle to thrive. By applying worm casts regularly, you can strengthen your plants’ natural defences against a range of common plant diseases. Some of the diseases that worm casts can help suppress include:
Soil-borne diseases
- Pythium root rot: This water-loving fungal disease affects the roots of plants,
- causing them to rot and wilt. The beneficial microorganisms in worm casts act as a ‘smoke screen’ so that pythium zoospores can’t hone in on your plants’ roots.
- Rhizoctonia and fusarium wilt: These soil-borne fungi cause root and stem rot, leading to stunted growth and plant death. As they do with pythium, worm castings introduce beneficial bacteria and fungi that disrupt the lifecycle of these pathogens, promoting healthier roots and stronger plants.
- Verticillium wilt: This persistent pathogen affects a wide variety of plants and is difficult to control once it takes hold. By introducing beneficial organisms, worm casts create a healthier root zone that discourages verticillium colonisation and supports resilient plant growth.
- Clubroot (Plasmodiophora brassicae): Affecting brassica crops, clubroot causes roots to swell and become distorted. The beneficial microbes in worm casts can help suppress clubroot by enhancing soil health and boosting the plant’s immune responses.
Foliar diseases
- Powdery mildew and botrytis (grey mould): Foliar diseases like powdery mildew and grey mould can spread rapidly, particularly in humid environments. Using worm tea made from worm casts can help create a microbial shield on plant leaves, reducing the spread of these fungal diseases.
- Early blight (Alternaria solani) and Tomato leaf spot (Septoria lycopersici): These fungal diseases are common in tomatoes and other solanaceous plants. Worm casts help bolster the soil’s microbial activity, making it more challenging for these pathogens to infect plants and damage foliage.
Worm casts don’t just provide immediate pest deterrence. They contribute to long-term soil and plant health, which strengthens your garden’s resilience over time. Apply Urban Wyrm worm casts regularly to build up a rich population of beneficial microbes in the soil, creating an inhospitable environment for pests year after year.
Ready to make your own worm tea to help prevent pests and diseases on your plants? Buy our 5-litre bag of pure worm casts and save up to 54% per litre.
