Question
i have a fusarium oxisporum caused disease on cactus and I like to find its fsp . could you please tell me how i do it

Answer
Hi Banafshe,

The only report I could find on fusarium oxysporum disease in cacti is in the American Phytopathological Society journal, _Plant Disease_, January 2004, Volume 88, Number 1

"First Report of Basal Stem Rot of Golden Barrel
Cactus Caused by Fusarium oxysporum f. sp.
opuntiarum in Italy"

So you may try to find a copy of that paper.  There are several references online to the f.sp.opuntiarum, but they are published in french and Portuguese.

If you want to know how to set up an experiment to determine whether what you have is f.sp. opuntiarum, you will need to have a pure culture of the f.sp. opuntiarium.  You can find information about _in vitro_ culture and microscopic examination at the following link:

http://www.doctorfungus.org/thefungi/Fusarium_oxysporum.htm

You would need to have also several cacti for test subjects.  You could then inoculate with the opuntiarium culture, compare the disease signs and symptoms to the ones that your cactus exhibits.

This requires a great deal of time, effort, and expertise.  It is rare that I get a question that refers specifically to a species name, much less a _forma specialis_.  What is your experience with plant pathology?

I will help as much as I can, but it is important to know exactly how I can help.