Muscardine: The Fungus That Mummifies Silkworms

An Insect-Killing Fungus

White muscardine is caused by Beauveria bassiana, an entomopathogenic fungus — one that makes its living killing insects. It attacks silkworms at the larval and pupal stages and causes serious losses to cocoon production.

How It Kills

Unlike a virus or a bacterium, this fungus does not need to be eaten. Spores germinate on the cuticle and grow through it, colonising the insect from the inside. The host dies, and the fungus then fruits back out through the body wall, coating the corpse in white spores — which is where the name comes from and why the result looks mummified.

The Same Fungus, Sold in a Bottle

The turn here mirrors grasserie. Beauveria bassiana is a commercial biological pesticide, used in agriculture and horticulture precisely because it kills insects without synthetic chemistry.

So the organism that devastates silkworm rearing houses is the same organism sold to growers as an environmentally-preferable way to control pests. Whether it is a disease or a tool depends entirely on which insect you are trying to keep alive.

The Practical Consequence

It is worth knowing if you keep both plants and feeder insects. A fungal insecticide applied to houseplants is not selective about which insects it meets, and spores persist. Treating a vivarium or a plant collection with a Beauveria product near a feeder culture is a genuine risk — the same reason wild-collected leaves are a gamble.

Related: the four silkworm diseases · raising silkworms at home