Pacific Northwest Plant Disease Management Handbook

Appressorium (pl. appressoria)

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Latest revision: 
March 2024

Conidium of Alternaria solani that has germinated on a potato leaf surface and formed several appressoria. (Dark elongate structure is the conidium while the dark circular object is an air bubble.)

Jay W. Pscheidt, 1980's.

a swollen, flattened portion of a fungal hyphae that adheres to the surface of a plant, providing anchorage for penetration into the tissue.

Pscheidt, J.W., and Ocamb, C.M. (Senior Eds.). 2026 Pacific Northwest Plant Disease Management Handbook.
© Oregon State University.

Use pesticides safely!

  • Wear protective clothing and safety devices as recommended on the label. Bathe or shower after each use.
  • Read the pesticide label—even if you’ve used the pesticide before. Follow closely the instructions on the label (and any other directions you have).
  • Be cautious when you apply pesticides. Know your legal responsibility as a pesticide applicator. You may be liable for injury or damage resulting from pesticide use.

Trade-name products and services are mentioned as illustrations only. This does not mean that the participating Extension Services endorse these products and services or that they intend to discriminate against products and services not mentioned.

H - Home garden packaging commonly available.     O - Acceptable in organic production.