it can be bacterial too. and bacterial is very hard to get rid off. I've been fighting something I think is bacterial fro sev years now on my one large philo. Azamax soil drench helped a lot to slow it down. I cut off and rerooted the tips which were less effected then older leaves. they were ok for half a year, but then strated showing the spots again. so azamax to the rescue..but it's tiresome.

my spots are different from yours though, and the plant still grows OK. I've been looking at philos in FL grown outside and they all have the signs.

Thank you. Now, I believe that Azamax is mainly a pesticide, so I'm pretty sure it won't work for me. As I said Daconil doesn't seem to work, so I'm skeptical that it is fungal. Is there an approach to dealing with bacterial infections?

Azamax acts as systemic - it's a very strong concentration of neem oil extract. it is fungicide/ miticide/pesticide/bactericide.

Ah, good to know. Thank you. So I should be spraying with Azamax regularly? More to the point, should I be spraying regularly with Azadirachtin, which is basically Neem oil? Concentration?

I use soil drenches of azamax, but spraying at the same time is good too. I am not familiar with azdirachtin and how it compares with Azamax.

neem oil by itself is not a very strong anti-fungal.

Well, Azamax is basically Neem oil, i understand, and Azdirachtin is the active ingredient in Neem oil. Same thing.