Think there is some kind of air toxin in the rain perhaps. I had something like this happen in early Summer, but not this drastic. Anything with tender leaves kicked the bucket. The wood on your tree still looks healthy. In Summer, many trees will kick back into life again and again even if all the leaves are picked off or eaten by bugs.

Hey, nature always finds a way. If nature gave up on us after the climate killed the dinosaurs, we would have been toast a long time ago.

Grow weeds if you have to. I would not say this is the end. You are right about not wasting too much time and resources on your exotic plants, veggies and fruits until you can figure this out though and whether or not its safe. I think you'll find there are still some green plants and flowers that might still be okay though.

Send your photos or a link to this page to the local extension service. In the US it's usually associated with the state college, where horticulture researchers offer to freely answer farmer, agriculture, forestry, and gardening questions. I'm sure they have something similar available in your country.