What is Protein Poisoning in Worms?

What is Protein Poisoning in Worms?

If you notice that worms are dying or your population has decreased by a significant amount, a possible issue is what's known as protein poisoning (aka string of pearls).

This condition is common but can be complex to diagnose, so let’s look at what causes string of pearls and protein poisoning, what to do about it, and most importantly how to avoid it in your worm bin!

What is Protein Poisoning in Worms?

Protein poisoning, also known as string of pearls, is a deadly condition that can affect compost worms (e.g., red wigglers) due to dietary issues. A combination of calcium deficiency, highly acidic or protein-rich foods, and a lack of grit disrupts worms’ digestive process, allowing gasses to form and rupture in their digestive tract. Protein poisoning is not contagious but is deadly for afflicted worms.

Why Worm Protein Poisoning is Called "String of Pearls"

The term "String of Pearls" refers to the distinctive appearance of worms suffering from protein poisoning. The worms have a beaded appearance, much like a string of pearls, with beads connected by stringy areas. String of pearls is the result of gasses building up and rupturing in a worms; digestive tract.

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What are the Causes of Protein Poisoning in Worms?

Protein poisoning in worms is caused by a combination of feeding worms foods that are acidic or rich in protein, lack of calcium in the worms’ diet, and fermentation which creates gasses that rupture in a worm’s digestive tract. In other words, if worms don’t have enough calcium in their diet to help process acidic food, fermentation occurs which gives off gasses that the worm can not pass through their digestive tract. The result is a rupture of the tract and ultimately death for the worm.

This is a complicated issue! 

Here is a more detailed explanation:

Worms take in food through openings in their head area. Worms don’t have teeth so they store grit near their mouths just like birds do. 

Food passes through the grit to grind up the food, and to help with digestion a gland releases calcium to coat and neutralize acid in the food.

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When worms’ diets lack calcium or grit, this digestive process is compromised. Throw in a diet high in acid or protein and protein poisoning becomes likely.

How Does Protein Poisoning Happen in Worms?

There are 4 common ways that protein poisoning happens in worms:

  • Worm bins are over-feed, which allows food to ferment and become more acidic with ammonia gas building up in the bin.
  • Worms are fed a diet too high in protein.
  • A lack of calcium (e.g., egg shells) in the worms' diet prevents worms from being able to digest acidic foods.
  • A lack of grit-like substances in the worm bedding prevents worms from properly grinding up food.
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Overfeeding a bin, esp. with acidic foods, can lead to worm protein poisoning


Here's the likely chain of events that leads to protein poisoning and string of pearls:

  • Too much food is placed into a too moist worm farm or bin.
  • Worms can not keep up and eat the food fast enough, so it begins to ferment. Ammonia levels rise and become an issue in the bin.
  • The worms don’t have enough grit or calcium in their diet which hampers their ability to process acidic foods.
  • Worms begin to consume the fermenting food. Their digestive systems are not sophisticated enough to process the fermented material.
  • Gasses begin to form in their digestive tract. Worms can't "pass gas" like humans do.
  • The gas levels build up and eventually rupture the digestive tract, leading to the "string of pearls" effect.

Symptoms of Protein Poisoning in Worms

The "String of Pearls" effect is the key physical sign that worms are sick from protein poisoning. Other symptoms of protein poisoning include worms becoming more lethargic, surfacing less, and slowing or stopping eating when bin conditions deteriorate as a result of protein poisoning. These behavioral changes are often the first sign of an unhealthy environment and should prompt an immediate assessment of their living conditions and diet.

symptoms of protein poisoning in worms, symptoms of string of pearls in worms

Compost worms live and eat on the surface, so if worms are not actively surfacing to eat, or they are not found feeding directly underneath food, this is a sign that problems exist in the worm bin. 

If you notice any of the symptoms mentioned above, it's important to consider protein poisoning as a potential cause. Paying attention to recent changes in worms’ eating habits and behavior can help identify issues before they spread.

Is Protein Poisoning Contagious in Worms?

No - protein poisoning is not contagious in worms. Worms afflicted with “string of pearls” will die, but other healthy worms will survive as long as the diet and worm bin issues causing protein poisoning are resolved. If diet and bin conditions are not resolved, it is likely that all worms in the bin will eventually perish.

How to Handle Protein Poisoning in Worms

If you suspect your worms are suffering from protein poisoning:

  • immediately remove any uneaten food from the bin.
  • mix in new bedding material, including shredded cardboard and crushed eggshell, to the existing bedding, and
  • add a new, fresh 3-4 inch layer of bedding on top. Moisten the bedding and add a small amount of food (e.g., ½ of a banana) on the top of the bedding.

The healthy worms left in your bin will come to the top and should begin eating the new food.

Worms may continue to die for a period of time but the above should address the issues and contribute to a healthy environment for the remaining worms.

How to Prevent Protein Poisoning in Worms

To prevent protein poisoning in worms, make sure the worms’ diet is not overly rich in protein, includes a calcium source like egg shells, and the worm bin is not overfed with too much food that the worms can’t consume in 2-3 days. It’s also important to incorporate more carbon-rich materials like shredded cardboard to balance the nitrogen-rich food scraps.

If you have access to a neutral pH food source like composted foods or manure, this will ensure the worms are not being fed foods that are or can become highly acidic.

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Finally, regularly monitor the worm bin to verify that worms are active, living on the surface, and are eating all of the food placed in the bin in a timely manner.

Frequently Asked Questions: Protein Poisoning in Worms

Can Protein Poisoning Be Reversed?

Protein poisoning can not be reversed in worms afflicted with it, but the issues in the worm bin that cause protein poisoning can be changed. To reverse the conditions causing protein poisoning, remove excess food from the bin, add a 3-4 inch layer of new, fresh, moistened bedding, and feed the worms a small amount of food on the surface of the bedding. Healthy worms will move to the top, begin feeding, and should survive.

How Quickly Do Protein Poisoning Symptoms?

It usually takes a few weeks of poor worm bin conditions for protein poisoning symptoms to appear in worms. During this time, uneaten food is fermenting in the bin.

Once that process happens, worms eat the food and are exposed to gasses in the fermented food. Worms are unable to process the gasses, which leads to a rupture in their digestive tract. Soon after the worms will perish.

What Happens to Worms When They Die?

When worms die their bodies begin to dry out, then harden, and then begin decomposition. Microorganisms such as bacteria and fungi help with this process. When worms decompose, beneficial biology is added to the surrounding soil. This process contributes nutrients within the composting system, ultimately enhancing the quality of the soil and vermicompost in the worm bin.

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