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Clara Henriette Hasse (1880 – 10 October 1926) was an American botanist whose research focused on plant pathology. She is known for identifying the cause of citrus canker, which was threatening crops in the Deep South.

Clara Henriette Hasse
Clara H Hasse.jpg
Died10 October 1926
Muskegon, Michigan
Alma materUniversity of Michigan
Known forIdentified the cause of citrus canker
Scientific career
FieldsBotanist focused on plant pathology
InstitutionsBureau of Plant Industry, U.S. Department of Agriculture; Florida Agricultural Experiment Station
Author abbrev. (botany)C.H.Hasse


After graduating from the University of Michigan in 1903 with a PhB.[1][2] She went to Washington, D.C., to take up an appointment as assistant horticulturist and botanist in the Bureau of Plant Industry at the U.S. Department of Agriculture under Erwin Frink Smith, the USDA's pathologist-in-charge.[1] Hasse was one of the twenty assistants that Smith hired during his tenure at the USDA. She later worked at the Florida Agricultural Experiment Station.[3] Hasse died at her home in Muskegon, Michigan, aged 46.[4]


Her paper "Pseudomonas citri, the cause of Citrus canker", published in the Journal of Agricultural Research in 1915, was the first to identify the cause of citrus canker. While originally it was believed that citrus canker was of fungoid origin, Hasse found that bacteria are at its source.[5]

Thomas Swann Harding credits this research with resulting "in control methods which prevented this disease from wiping out the citrus crop in Florida, Alabama, Mississippi, and Texas."[6]

Partial bibliographyEdit

  • Pseudomonas citri, the cause of Citrus canker (1915). Journal of Agricultural Research


  1. ^ a b Rossiter, Margaret W. (September 1980). ""Women's Work" in Science, 1880-1910". Isis. The University of Chicago Press on behalf of The History of Science Society. 71 (3): 381–398. doi:10.1086/352540. JSTOR 230118.
  2. ^ Michigan, University of (1900-01-01). Calendar of the University of Michigan for ... The University.
  3. ^ "Clara H. Hasse (1880?-1926)". Collection Record. Smithsonian Institution Archives. Retrieved 30 March 2012.
  4. ^ The Michigan Alumnus (1926), Volume 33, p. 284
  5. ^ PSEUDOMONAS CITRI, THE CAUSE OF CITRUS CANKER ( book reader)PSEUDOMONAS CITRI, THE CAUSE OF CITRUS CANKER ( text version), Clara Hasse, Journal of Agricultural Research, 2015-10, Volume 4, p. 97.
  6. ^ Thomas Swann Harding (1947). Two Blades Of Grass. Norman University Of Oklahoma Press. p. 324.
  7. ^ IPNI.  C.H.Hasse.

External linksEdit