Flacherie: The Silkworm Disease That Comes From Food

A Disease You Feed Them

Flacherie is caused by silkworms eating infected or contaminated mulberry leaves. Unlike pébrine, which arrives in the egg, or muscardine, which arrives as fungal spores, flacherie comes in with the food.

Two Different Things Under One Name

The name covers two conditions that look similar and are not the same:

• Infectious flacherie — viral, transmitted through contaminated leaf.
• Touffée — non-infectious, brought on by heat stress rather than a pathogen.

Both are, in practical terms, a lethal diarrhoea. The larva goes limp and slack — "flacherie" shares a root with flaccid — stops feeding, and dies.

Why the Distinction Matters

An outbreak of infectious flacherie is a contamination problem: the leaf source, the handling, the hygiene of the rearing space. Touffée is an environment problem: the room got too hot and stayed there. Same symptoms, completely different fix.

What It Means for a Cup on a Shelf

Flacherie is the silkworm disease with the clearest lesson for anyone keeping a small quantity: the food is the risk. Stale chow, leaves left to sit and sour, a container kept somewhere warm — those are the conditions that produce limp, non-feeding worms at home.

It also explains a rule that otherwise sounds fussy: replace food rather than topping it up. Old food at the bottom of a container is where this begins.

Related: the four silkworm diseases · raising silkworms at home