> French sericulture, silkworm disease and Pasteur’s work at Alès in 1865–1870: how microscopy and egg selection changed an agricultural industry.

Source: https://husfarm.com/history/silkworm-crisis-pasteur-pebrine-1865-1870/

[Home](https://husfarm.com/)›[History of agriculture](https://husfarm.com/history/)›[Industrial era](https://husfarm.com/history/era/industrial-era/)›The silkworm crisis and Pasteur’s investigations[Industrial era](https://husfarm.com/history/era/industrial-era/)·[Science & experiments](https://husfarm.com/history/topic/science-and-experiments/)

# The silkworm crisis and Pasteur’s investigations

In the middle of the nineteenth century, silkworm diseases disrupted the economies of many communities in southern France. More than the production of a luxury fabric was at risk. The crisis affected mulberry cultivation, seasonal work feeding caterpillars, the trade in eggs and the sale of cocoons. Louis Pasteur’s investigations around Alès, begun in 1865, helped transform the assessment of breeding material. The microscope became a practical agricultural instrument, used to select batches of eggs by examining their parents. This was prevention through selection, not vaccination of silkworms.
By the [Husfarm editorial team](https://husfarm.com/about_us/) · Published 26 October 2026 · 13 sources cited
Date1840s–1870s; Pasteur’s investigations 1865–1870
PlaceAlès and the Cévennes, southern France; European and Asian sericulture networks
Era[Industrial era](https://husfarm.com/history/era/industrial-era/)from c. 1800
Region · subject[Europe](https://husfarm.com/history/region/europe/)Science & experiments
Reading time7 min1477 words
Topic 59 of 100 on the timeline[Prehistorybefore c. 3000 BCE13 topics](https://husfarm.com/history/era/prehistory/)[Antiquityc. 3000 BCE – 500 CE10 topics](https://husfarm.com/history/era/antiquity/)[Middle Agesc. 500–150016 topics](https://husfarm.com/history/era/middle-ages/)[Early modernc. 1500–18007 topics](https://husfarm.com/history/era/early-modern/)[Industrial erafrom c. 180054 topics](https://husfarm.com/history/era/industrial-era/)

Silkworm cocoons used by Louis Pasteur in his studies, 1865–1870. Wellcome Collection · [Wikimedia Commons](https://commons.wikimedia.org/wiki/File:String_of_silkworm_cocoons,_used_by_Louis_Pasteur,_1865-1870_Wellcome_L0057278.jpg) · [CC BY 4.0](https://creativecommons.org/licenses/by/4.0)

## In this article

- [Silk began with mulberry trees and farm labour](#sec-1)
- [The crisis was established before Pasteur arrived](#sec-2)
- [Muscardine, pébrine and flacherie were different problems](#sec-3)
- [Alès: a laboratory within the landscape of sericulture](#sec-4)
- [Cellular grainage and the identity of an egg batch](#sec-5)
- [Why a single examination could not solve every difficulty](#sec-6)
- [From the microscope to an organised market in breeding stock](#sec-7)
- [Scientific achievement and the limits of a rescue narrative](#sec-8)
- [Questions and answers](#hi-faq)
- [Sources](#hi-src)

## Key dates

- **1835–1836**Bassi publishes work on fungal muscardine, a disease distinct from pébrine.[4](#src-silk-bassi)[3](#src-silk-asm)
- **1849**Pasteur later records widespread rearing failures in this year and an expanding egg trade.[1](#src-silk-pasteur-book)
- **1865**Pasteur begins his investigation around Alès.[9](#src-silk-house)[2](#src-silk-institut)[8](#src-silk-archives)
- **1868–1869**Further selection trials and successive rearings test the method’s usefulness.[1](#src-silk-pasteur-book)[5](#src-silk-carton)
- **1870**Publication of the two-volume Études sur la maladie des vers à soie.[11](#src-silk-wellcome)[1](#src-silk-pasteur-book)
- **1870**The sericulture congress at Gorizia supports international circulation of knowledge about selection.[6](#src-silk-georgia)

## Silk began with mulberry trees and farm labour

The mulberry silkworm, Bombyx mori, connected fibre production to the rhythm of vegetation. Its caterpillars required mulberry leaves, so rearing depended on trees, suitable indoor space and the labour of collecting and delivering food. After growing, the larvae spun cocoons in which further metamorphosis took place. Some insects were retained for reproduction; other cocoons entered processing. Agricultural cocoon production and the industrial reeling of silk thread were connected but distinct stages, with different tasks and sources of income.
In the Cévennes, sericulture supplemented farm earnings and gave value to mulberry plantations. Losing a rearing meant losing work already invested in trees and feeding. The consequences also reached factories employing many women. The Maison Rouge museum records 23 establishments working with silk in Saint-Jean-du-Gard in 1856, employing 1,090 women and 150 men. This is a local industrial workforce count, not a total of silkworm rearers. Nevertheless, it demonstrates why the disease of an insect could become a problem for an entire local economy.[1](#src-silk-pasteur-book)[10](#src-silk-maison)[13](#src-silk-rearing)

## The crisis was established before Pasteur arrived

Pasteur entered a region already familiar with repeated failures. In his 1870 book he recorded recollections of losses in the mid-1840s and conspicuous failures from 1849 onwards. The epidemic therefore began before his official mission. Disease did not appear everywhere simultaneously, and its spread did not immediately have to reduce the national harvest. Expanding production and purchasing eggs from other districts could temporarily conceal the damage, creating the apparent contradiction of increasing output alongside worsening local experience.
Merchants sought healthy stock in Lombardy and then in further silk-producing areas. Imports of Japanese eggs later became significant. Distance from an affected district did not itself guarantee safety, however, and material with an uncertain history entered the trade. Pasteur described successful rearings that produced apparently promising cocoons but disappointing offspring in the following generation. The problem concerned the continuity of reproduction, rather than the appearance of a single harvest. Buyers needed information about the health of a future rearing that could not simply be inferred from attractive eggs or the value of the previous crop.[1](#src-silk-pasteur-book)

## Muscardine, pébrine and flacherie were different problems

Pasteur’s investigations had an important predecessor. In 1835–1836 Agostino Bassi published his work on muscardine, a silkworm disease caused by the fungus now called Beauveria bassiana. He associated its transmission with the movement of fungal spores. This was a different disease from the pébrine subsequently investigated by Pasteur. Merging both episodes into one silkworm plague obscures a significant part of the history of understanding infection and the contributions made before the French investigations.
Pébrine is associated with the microsporidian Nosema bombycis. Nineteenth-century microscopists observed distinctive small bodies, but disagreed about their nature and significance. Flacherie, meanwhile, covered episodes in which caterpillars became flaccid and died, without pébrine alone explaining the losses. Modern knowledge identifies a more complex set of causes, including bacterial and viral agents. The historical term should therefore not be equated with one simple diagnosis. Distinguishing these problems helped explain why a method effective against one disease did not automatically guarantee a successful rearing in every respect.[4](#src-silk-bassi)[3](#src-silk-asm)[1](#src-silk-pasteur-book)[5](#src-silk-carton)

## Alès: a laboratory within the landscape of sericulture

In 1865, following the intervention of Jean-Baptiste Dumas and the French government, Pasteur began work in southern France. Alès, also written Alais in contemporary publications, became the main centre of the investigation. The house at Pont-Gisquet, in present-day Saint-Jean-du-Pin, is associated with this work. Laboratory and rearing spaces stood close to working sericultural communities, allowing microscopic findings to be compared with events in actual production. The landscape of the research included houses, mulberry trees and farmers as well as scientific instruments.
Work extended across successive seasons and followed larvae, cocoons, pupae, moths and their offspring. Collaborators included Duclaux, Gernez, Maillot and Raulin. It was not a complete diagnosis delivered at the first glance through a microscope: Pasteur initially misinterpreted the nature of the bodies associated with pébrine and revised his views. Surviving cocoons in the Science Museum Group collection and records in the Alès archives recall the material work behind the investigation. Samples, comparison groups, identifying labels and the time needed for another generation were all necessary to test an explanation.[9](#src-silk-house)[8](#src-silk-archives)[7](#src-silk-smg)[1](#src-silk-pasteur-book)[5](#src-silk-carton)[12](#src-silk-ideev)

## Cellular grainage and the identity of an egg batch

In the language of sericulture, graine meant silkworm eggs, while grainage referred to producing eggs for subsequent rearing. Cellular selection separated moths or parental pairs and preserved the connection between those parents and their batch of eggs. After laying, the parent insects underwent microscopic examination. Material associated with the characteristic pébrine bodies was rejected; batches with an acceptable examination result were retained. “Cellular” referred to this separated arrangement, not to the laboratory culture of biological cells in its present-day sense.
The identifying procedure was as important as the instrument. If eggs from different families were mixed before the preparations were assessed, the result could no longer identify which batch to discard. Separate containers, labels and records were therefore essential. The criterion of quality changed: a large, marketable cocoon was insufficient proof that its insect should become a parent. Inspection addressed material on which the next season depended. It selected reproductive families rather than attempting to recover every loss only after visibly sick caterpillars had appeared in a commercial rearing.[2](#src-silk-institut)[6](#src-silk-georgia)[1](#src-silk-pasteur-book)

## Why a single examination could not solve every difficulty

The investigations showed that infection could pass between generations with reproductive material, while also spreading during rearing. In experiments described by Pasteur, food, contaminated material and surroundings occupied by diseased insects mattered. Nineteenth-century references to the “heredity” of disease must be understood in that setting. They describe the transmission of infection between parents and offspring, rather than demonstrating the inheritance of a trait according to genetic laws. The distinction explains why selecting parental stock could interrupt an apparent family history of illness.
Another essential distinction separated the health of breeding material from the success of a current cocoon harvest. Larvae could produce valuable cocoons while a later developmental stage revealed infection. Conversely, failure in the absence of the characteristic bodies encouraged investigation of another disease, including flacherie. These complications made rearing conditions and comparison through time significant. Egg selection was a powerful means of limiting pébrine, but it neither demonstrated immunity to every disease nor cured an already infected silkworm. The achievement was a more dependable starting point for husbandry, not the removal of every biological uncertainty.[1](#src-silk-pasteur-book)[2](#src-silk-institut)[3](#src-silk-asm)

## From the microscope to an organised market in breeding stock

Introducing the method required more than acquiring an instrument. Someone had to prepare a specimen, recognise the relevant bodies, record the result and maintain the separation of batches. An egg producer and the farmer using that material in the following season both had to trust those operations. Quality assessment partly moved from the appearance of goods and a merchant’s reputation towards a repeatable examination. Early discussions even considered making microscopes available within local communities so that access to inspection need not depend solely on an individual household’s equipment.
Experiments, publications and specialised organisations carried the practice further. The State Silk Museum in Tbilisi points to the international sericulture congress at Gorizia in 1870 and to stations, including those in the Caucasus, that examined and distributed healthy eggs. This later development does not imply identical adoption in every country. It shows that the technique could travel together with a working procedure. Its usefulness depended on maintaining a link between the recorded examination and the actual material delivered to a rearer. Laboratory knowledge became effective through an organised chain of people, labels and transactions.[1](#src-silk-pasteur-book)[6](#src-silk-georgia)

## Scientific achievement and the limits of a rescue narrative

In 1870 Pasteur published the two-volume Études sur la maladie des vers à soie. The first volume discussed pébrine and flacherie; the second collected notes and documents. The publication preserved experiments and disputes from which a practical preventive system had emerged. Its illustrations and descriptions of rearings showed how a farming problem could be investigated by combining detailed laboratory observations with comparison across production cycles. The work became an important stage in the development of a microbial understanding of disease.
Saying that Pasteur “saved sericulture” conveys the importance of his contribution but simplifies the industry’s subsequent history. Limiting pébrine could not automatically restore every mulberry plantation, farm income or job, and his own description of the crisis documented dependence on international trade. French processing establishments had a separate, longer history: Maison Rouge did not close until 1965. The enduring legacy is more precise than a single moment of rescue. The health of reproductive material became an object of systematic investigation and quality control, rather than merely a buyer’s hope about the coming season.[11](#src-silk-wellcome)[1](#src-silk-pasteur-book)[10](#src-silk-maison)[12](#src-silk-ideev)

## Questions and answers

Did Pasteur vaccinate silkworms against pébrine?No. The central method examined parent moths and selected the batches of eggs connected to them. It aimed to limit transmission into the next rearing, rather than vaccinating silkworms or treating every sick caterpillar.[2](#src-silk-institut)[1](#src-silk-pasteur-book)
Why examine moths when the losses affected caterpillars?The appearance of cocoons and a successful individual harvest did not establish the health of the next generation. Examining parents allowed associated egg batches to be assessed while keeping their identities separate.[2](#src-silk-institut)[6](#src-silk-georgia)[1](#src-silk-pasteur-book)
Were Bassi and Pasteur studying the same disease?No. Bassi linked muscardine to a fungus whose spores spread infection. Pasteur later investigated pébrine and flacherie. Together these investigations contributed to understanding several distinct silkworm diseases.[4](#src-silk-bassi)[3](#src-silk-asm)[1](#src-silk-pasteur-book)

## Sources

- Louis Pasteur (1870). [Études sur la maladie des vers à soie. Tome I: La pébrine et la flacherie; Wellcome Library copy](https://archive.org/details/b28124583_0001)
- Institut Pasteur (2016). [The middle years 1862–1877 — Silkworm diseases](https://www.pasteur.fr/en/about-us/middle-years-1862-1877)
- Brian Lovett / American Society for Microbiology (2019). [Sick or Silk: How Silkworms Spun the Germ Theory of Disease](https://asm.org/articles/2019/december/sick-or-silk-how-silkworms-spun-the-germ-theory-of)
- William B. Ashworth Jr. / Linda Hall Library (2024). [Agostino Bassi — Scientist of the Day](https://www.lindahall.org/about/news/scientist-of-the-day/agostino-bassi/)
- Yves Carton (2022). [Louis Pasteur face à la maladie du ver à soie (1865–1870): du chimiste au biologiste; author-deposited full text, DOI 10.5802/crchim.204](https://www.researchgate.net/publication/364254496_Louis_Pasteur_face_a_la_maladie_du_ver_a_soie_1865-1870_du_chimiste_au_biologiste)
- State Silk Museum, Tbilisi (n.d.). [Louis Pasteur](https://silkmuseum.ge/en/about/persons/article/4/louis-pasteur)
- Science Museum Group (n.d.). [String of silkworm cocoons, used by Louis Pasteur, 1865–1870; object A63336](https://collection.sciencemuseumgroup.org.uk/objects/co117653/string-of-silkworm-cocoons-used-by-louis-pasteur-1865-1870)
- Archives municipales d’Alès (2017). [Grainage et industrie de la soie; CD 1/20, related Pathéorama film no. 147](https://archives.ales.fr/ark:/55408/2c9081t7qlhv)
- Cévennes Tourisme / SPL Alès Cévennes (2026). [La Maison Pasteur à St Jean du Pin](https://www.cevennes-tourisme.fr/visites-decouvertes/la-maison-pasteur-a-st-jean-du-pin-saint-jean-du-pin-fr-4312987/)
- Maison Rouge — Musée des vallées cévenoles (n.d.). [Le bâtiment](https://www.maisonrouge-musee.fr/page-musee/le-batiment/)
- Wellcome Collection (1870). [Études sur la maladie des vers à soie / par L. Pasteur — bibliographic record](https://content.www.wellcomecollection.org/works/nrmhjqqn)
- Institut Diversité, Écologie et Évolution du Vivant, Université Paris-Saclay (2023). [Louis Pasteur face à la maladie du ver à soie (1865–1870): du chimiste au biologiste — Yves Carton seminar](https://www.ideev.universite-paris-saclay.fr/en/seminaires/2023/01/louis-pasteur-face-%C3%A0-la-maladie-du-ver-%C3%A0-soie-1865-1870-du-chimiste-au-biologiste/)
- Musée de la Soie, Saint-Hippolyte-du-Fort (n.d.). [Élevage — cycle du ver à soie et alimentation par feuilles de mûrier](https://museedelasoie-cevennes.com/elevage/)
Approximate dates (c.) describe the nature of the evidence: archaeology dates settlements, layers and remains, not single moments of invention.

[← Earlier · 1845–1852The Great Irish Famine: Farming, Poverty and Migration](https://husfarm.com/history/great-irish-famine-1845-1852/)[Later · From 1848 →Chicago Board of Trade: Grain, Contracts and Market Rules](https://husfarm.com/history/chicago-board-of-trade-1848-grain-futures-history/)

### Where

[59Alès · southern France](https://husfarm.com/history/silkworm-crisis-pasteur-pebrine-1865-1870/)
Points mark approximate areas, not exact sites or the borders of ancient cultures. Base map: Natural Earth, public domain.**Alès and the Cévennes, southern France; European and Asian sericulture networks**

### Related topics

[1843 · Industrial eraRothamsted since 1843: fields that became a scientific archive](https://husfarm.com/history/rothamsted-broadbalk-long-term-experiments-1843/)[2 July 1862 · Industrial eraThe Morrill Act of 1862: Colleges, Experiments and Agricultural Extension](https://husfarm.com/history/morrill-act-1862-colleges-research-agricultural-extension/)[1856–1863 · Industrial eraMendel and peas: making inheritance a quantitative question](https://husfarm.com/history/mendel-peas-inheritance-plant-breeding-1865/)[1885 · Industrial eraMycorrhiza: fungi in plant nutrition](https://husfarm.com/history/mycorrhiza-frank-1885-fungi-roots-agriculture/)

### Browse

[All topics 100](https://husfarm.com/history/)[Industrial era 54](https://husfarm.com/history/era/industrial-era/)[Europe 34](https://husfarm.com/history/region/europe/)[Science & experiments 16](https://husfarm.com/history/topic/science-and-experiments/)

## The same story in today’s markets

Where this part of farming history meets the prices, companies and shows we follow now.
[Other: today’s wholesale prices→](https://husfarm.com/products/other/)[Largest livestock genetics, equipment and health companies→](https://husfarm.com/agribusiness/sector/livestock/)[Agricultural trade fairs today→](https://husfarm.com/events/sector/general/)

[← History of agriculture: all topics](https://husfarm.com/history/)

---
Husfarm: https://husfarm.com/ · Site guide for agents: https://husfarm.com/llms.txt