Rosemary diseases on leaf after cutting

Rosemary    Italy

Good evening, sometimes we have a problem in some of our rosemary plant, cultivated in pot. We are in Italy, Province of Livorno, and in september, after our cutting operation, leaf of the low part of plant became ill and look like in the photos I have just posted.

We have a doubt: is this problem Peronospora lami or Alternaria sp? We believe that is the second one.

Thank you.

Posted by: Alessandro Caroti (1 point)  Alessandro Caroti
Posted: November 20, 2017

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Hi Alessandro, the best way to identify the disease is looking for spores. Do you have microscope facility?

The microscopic examination of Peronospora lamii should reveal mycelia with irregular dichotomously branched conidiophores with pointed tips and brown oval conidia.


Whereas the Alternaria spores are club shaped.


Posted by: Dr. Ravishankar Narayana (134 points) Dr. Ravishankar Narayana
Posted: November 21, 2017

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Alessandro Caroti commented,
Thank you Dr. Narayana for your answer and photos. In this moment I don't have any microscope facilty, but I'll try to organized. Thank
3 months ago.

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