Garden Pests and Diseases: Petunias dying soon after planting.., 2 by Gitagal

Gitagal wrote:
Dr. O--
Goodness! They sure look the same!! You are not far from me..One state up.
We just have not had "Hot dry" conditions....mostly Hot WET!

Should I assume it came WITH the plants? From the Nursery/Growers?
I have such a load of flowers in one of the beds...and these seem to be
the only ones dying off...that i can see...
The Petunias I planted earlier (Mid May) seem to be OK. How come?
Same weather conditions...same beds....

I DO have to say that my Begonia Grandis leaves are starting to show
signs of Fungus--or whatever---the leaves are getting spotty and look like
sections are rotting...BUT--I imagine that NO begonias like downpours
every other day, with no respite from the high temps and the Humidity
that the rains produce...
The affected plant's roots do feel and look rotted when I pulled them up.
Mushy!

I do not have chlorothalonil.
--Does it come under some Brand name in Big Box stores? I work at a HD.
How about Daconil? Been meaning to buy that anyway?
--How should i go about treating the Phytophthora crown rot.?
--Does it spread to other plants? Or--does it just stay in the area the
sick plants were?
--Do I dig up the soil around the plant's root base and discard it?
--How would I use the chlorothalonil? Soak the soil--spray all other plants?
--Is it "plant specific"? Like--ONLY petunias???
--Could I plant annual Dianthus in these spots to fill in?

Here is a picture of some of the beds--so many pretty plants in it...
These Petunias were in front...in several places.

Lots of Questions--but I thank you! Gita