Worms are Dying in Worm Bin (Part 3 of 4)

Worms dying in your bin is one of the trickiest problems in worm composting to identify and deal with because in many cases it is difficult to see that the worms are dying. When compost worms die, they dry out very quickly and blend in with dirt, compost, or castings very well.

In some cases, diagnosing issues causing worms to die in your bins can be simple. If, for example, the bin gets too dry, the worms may dry out and the issues causing their death will be obvious.

However, if you notice that worms are dying or your population has decreased by a significant amount, the most likely issue is what's known as "sour crop" (it's sometimes called protein poisoning as well, but that term is a bit misleading). This condition is common but can be complex to diagnose.

Sour crop most likely stems from a combination of:

  • Over-feeding your worms, which allows food to ferment and become more acidic.
  • Lack of calcium in the worms' diet.
  • Lack of grit-like substances worms use to grind food (since they don't have any teeth to help out!).

When worms eat, they use grit in their crops to grind food - similar to the process that birds use - and coat the food with calcium to aid the digestive process. In the absence of grit or calcium, this process isn't completed and food is passed into the digestive tract where it can ferment and create gases the worms can not "pass". The gas will build inside the worm, eventually rupture their intestines, and the worms will die. This condition is often called "string of pearls" because the worms' bodies resemble a string of pearls when they have (and die from) from this condition. 

The bad news with "string of pearls" is that worms will not recover from it, but the good news is that it isn't contagious to other worms (though the bin conditions creating it can result in most worms having string of pearls).

If you discover string of pearls or other issues where worms are dying, try the following steps to get your bin back on track:

  • Remove all food from the bin.
  • Remove any string of pearls worms you find.
  • Gently look around in the bin to see if there are live, healthy worms. Live and healthy means no deformities and moving around in the bin.
  • Check to see if there is surface activity - are healthy worms moving around in the top 1-2 inches of the bin?

If you don't see any live, healthy worms, then you may be faced with a situation where the population died quickly and you'll need to start a new bin or tray from scratch. 

If you see live, healthy worms, we recommend the following steps:

  • Remove all food
  • Mix in new, damp bedding (1/4 to 1/2 what you already have in the bin) mixed with crushed egg shells.
  • Monitor the bin for a day or 2 and then add a small amount of food (1/4 pound per pound of worms).

Continue feeding the worms every few days as the new food is fully processed, and monitor for any more string of pearl worms.  It may take some time to re-balance the bins to a healthy condition, so be patient feeding and disturbing the worms as they re-acclimate.

If you're still struggling with issues in your bin, try our other posts in this series on troubleshooting issues in your worm bins:


Brothers Worm Farm

I’ve had a vermicomposter for 20+ years with no problems. All of a sudden I discovered all of my worms died and the compost was black and slimy looking. Any ideas what happened?

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