I got it to work
I found this suggestion from edwmax:
To post the image in a thread use the BB code '[img]___URL___[/img]' without the single quote marks and no spaces.
So I took the bulletin board code and inserted my URL and it finally worked.
I have spent hours trying to get this to work. I didn't realize that there are many other pages to the "How to post images in your threads" and the info from the first page is helpful but not completely.
Now I can post the thread to get my bananas identified.
Hope this helps someone else.
[img][
]Banana Gallery - red patches only on small new leaves