Leaf spot on Tulip tree - cause?

[buffalo606]

It's been a very dry summer in France and customer said Tulip tree began to lose leaves during the summer. The tree is 25 years old in a raised circular bed in courtyard and surrounded by gravel parking.

 

Leaf spots are black and not raised. They may have been sticky in the summer but are not now.

 

Could this be a drought reaction? Does this tree need a better watering scheme. She wants to fell it if spots and early leaf drop continue, which would be a real big shame.

[10 Bears]

To my eye, this looks like a bacterial leaf spot problem due to the obvious black spot but also halo'd by yellowed tissue. Could be related to Pseudomonas spp. or Xanthomonas spp. vectors. I believe these vectors can be airborne or travel short distances in contaminated water from rain splash or similar.

[gooseflight]

The yellow halo says Septoria to me -- fungal. Common in Magnolias -- Liriodendron is a relative.

 

Rake up and burn the fallen leaves.