Insect Frass – Complete Guide for Gardeners

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Insect frass is another term for insect feces. That’s right, insect frass = insect poop. It may be small, but it is very, very good for your garden and a hidden benefit of attracting many beneficial insects to your garden.

Insect frass contains a unique chemical mix of nutrients that act as a natural super-fertilizer for your garden. It naturally occurs in small quantities (if you have bugs, you have insect frass), but can also be purchased in bulk as a fertilizer. Mealworm castings are one of the most common forms of insect poop produced commercially.

What Does Insect Frass Look Like?

The frass in your garden will look different, depending on which insect it comes from. Colors can include yellow, brown, and black.  In some cases, you’ll see it as a liquid, smudged on or around leaves. If harvested for fertilizers, this liquid is scraped up and then turned into a powder. Or you may see it as micro-droppings, which undergo the same dehydration and powdering process for a fertilizer harvest.

What Benefits Does Insect Frass Provide?

Frass provides a wide range of benefits for your plants. The nutrients it contains, including nitrogen & potassium, can help improve your soil and regulate oxygen production in plants and help them to flower, encouraging solid growth. 

Frass is sometimes sold with insect exoskeletons included (usually sold as frass and casings), which acts in a similar way to adding bone meal (phosphorus) to your soil, and can help benefit the overall soil nutrient levels. It is a particularly useful food for young seedlings (add some prior to planting) and more vulnerable crops, or those suffering from repeated attacks from pests. 

Insect frass also contains chitin, which helps plants maintain strong and stable cell walls. Chitin is a close relative of cellulose and, when added to your plants’ soil, can also help to reduce powdery mildew, and act as an antibody that helps to resist pests and microbes, such as root nematodes. Chitin also helps to fight pathogens in the soil.

Chitin works to bolster plants by tricking them into thinking that they are being eaten by insects. This causes them to react by strengthening their cell walls. Chitin also helps with a plant’s immunity, as it contains antibodies that are used by both the plants and the surrounding soil. Using a lot of frass can also help benefit a soil’s pH level, making it more acidic (chitin has a pH level of around 3). 

Should I Purchase Insect Frass as a Fertilizer?

Insect frass, like other animal-based fertilizers such as horse manure and bone meal, is extremely beneficial for growing sturdy and abundant crops. 

While you almost inevitably have insect frass in your vegetable or herb garden already, this is a nutrient that your soil can certainly benefit from having more of than your local bugs can produce. If you want to go hunting for it, look in and under your leaves and around the very surface of the ground. However, if you just rely on the insects in your garden, you won’t be getting that much of it – which is why some gardeners prefer to purchase it in bulk.

Adding insect frass to your soil can help to add vital goodness to your garden. It is commercially available and is great for organic gardeners. If you can’t find it in your local specialty garden center, try reaching out to breeders of crickets, butterflies, or mealworms who may sell you frass directly.

How Do I Use Insect Frass?

Frass is often applied as a foliar spray. Mix five grams of dried frass per gallon of water and use a light sprinkler to water the plants and surrounding soil with the mix. It’s especially valuable for watering smaller, more fragile plants and seedlings. It also works very well mixed with liquid kelp (seaweed) diluted into your watering mix. 

You can also mix one pound of dried frass over a space of around 20 feet of raised beds or vegetable plots. Mix gently through the topsoil, then water the area well with a fine mist (to avoid rinsing the frass away). You may also prefer to try it as part of a root drench – it’s pretty flexible!

Frass is not a pesticide, which means it will not attack or damage other beneficial insects in your garden and can be used in organic and biodynamic gardens. It also does not add everything your soil and plants need, so don’t forget your compost.

Other Questions

What should I use if I can’t get Insect Frass?

If you need a nutrient-dense fertilizer but can’t get insect frass, you may wish to consider the following:

  • Animal manure or dung
  • Bone meal
  • Seaweed based nutrients, such as kelp
  • Potash
  • Specific chemical compound fertilizers

What is Insect Frass Tea?

You may have heard someone refer to insect frass tea – this is a term sometimes used for the liquid form used in a root drench. Do not drink insect frass!

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