For me is a C. imbricata, is the most conspicuous species, and is the easiest to see in the field. I dont know where you find it, but the distribution range of the plant is also an indicative of the specie; C. fulgida is limited to the Sonora desert, and C. imbricate occupies almost all the US south and northern Mexico. Of course, the flowers will be perfect to the identification. 

Dear Jean-Marc,

Both Hildegard Klein and Pieter Winter suggest that it is likely to be Cylindropuntia imbricata.

Kind regards

Philip

Thank you very much. Its was found far away from its native range: In Israel... I hope it will not become invasive also in this part of the world. I am a little bit concerned because lately Cylindropuntia species were recorded as invasive in Spain.

Is there a reliable way to distinguish C. imbricata from C. fulgida?

Thanks

Jean-Marc

It seems Cylindropuntia imbricata, but more prickly than usual.

Best regards,

It is C. imbricata

Dear Colleagues, Thank you very much for your help.

I also agree on Cylindropuntia imbricata

Cylindropuntia imbricata, no doubt.

Cylindropuntia imbricata

It is surely Cylindropuntia imbricata Haw. (DC.) (syn. Opuntia imbricata) of Cactaceae family. It native range includes arid regions of United States and Mexico.

Thank you !