Thanks for reposting!! I was going to respond when you posted initially but was unable to comment due to that stupid (and utterly useless) forum included as a cross post.

You might want to Google 'pittosporum sudden death', as this phenomenon is very common in SoCal where these plants are very popular and widely used. Apparently a root rot can be the culprit and there is also the possibility of some larval insect that eats the roots.

I did search for a while, but I will look again.

I am not sure about the root rot, but maybe that is the problem. At first, I thought it was too little water, but heard from someone else about root rot and that made me think more about what has been going on as of late. With these daily rains, and my next door neighbor's higher ground, perhaps that area is getting/retaining too much water.

The conundrum with this notion is that it has rained down here like that all summer long, year after year after year, but these shrubs have only had a problem within the last couple of years.

eventually a box did appear for posting in.. and this is what i posted at the other link:

starting with the third year.. i never water shrubs ...

i suspect its a watering issue.. especially when you mentioned the neighbor was watering them in addition to your watering ... what is your native soil .. and does it drain ????

if you are going to hang around.. and i hope you do.. plz add your location on your members page .. so it appears in every post ...

your big city location might give us the ability to discuss whether there is some local issue .... in regard to this particular plant ....

ken

and you thanked me.. and you are welcome ... ken

https://www.houzz.com/discussions/pittosporums-dying-dsvw-vd~5416703?n=1

Thank you for re-posting too! I will update profile with my location - Central Florida. So, soil is mostly sand. These pittosporums have been there for nearly 30 years. So, as I said in above post, it is very confusing why the watering would become an issue over the past couple of years only.

A little closer look (see new pics) shows brown spots - unfortunately not only on the dying one but the others as well. I am guessing those are going to go too within the next year. I can't tell by these photos whether or not it could be some sort of insect, but probably more likely fungus-related. I am going to see if I can find any similar pics on the internet.

Yep - I think you are right. But, if it is root rot, do I have to worry about soil treatment or something before planting another type of shrub?

Also, if it is truly a drainage problem, going to need to find something that doesn't mind being moist, but can handle periods of dryness as well.

Various root rots can affect pitts and some will prevent replanting with a similar species or even any number of other susceptible plants due to their persistence in the soil. I would suggest you remove the dead/dying one and take (intact) to your local extension office for a complete diagnosis. They may need to send to their pathology lab for a full evaluation but once you know exactly what is causing the die-off, you will be better able to determine what will grow well under those conditions.

Thanks. I haven't taken a plant sample to anyone yet, but I did send pics and info/questions to my local extension office who has responded by saying that the pitts look nutrient-deprived - likely further aggravated by excess water 'leeching' nutrients out of the sandy soil. Also, recommended I have soil tested for PH and nutrients. Never mentioned root rot, and said I might get new growth on them - but didn't say how. I typically put slow-release fertilizer on them twice a year, but this year forwent the fertilizer because of the way the were looking this spring.

The thing that is blowing my mind about all of this is the fact nothing has really changed in the condition surrounding these pittosporums - like as in forever.

Nutrient deprivation may cause stunting or slow or sparse growth but it will not cause wilting or die-off!!

Most root rots are oomycetes, or water molds so the pathogens move through the soil with water flow. So it is not necessarily just a case of poor drainage but could just be a case of excess run-off that included some already contaminated water flow. the problem seems to be that pitts are overly sensitive to these sorts of pathogens. If you read up on pittosporum die-off, you will get an indication of how commonplace this issue is, even in quite arid climates like SoCal!!