A friend was asking me today about the sudden death of some of his viburnums. He didn't know the variety, but they are planted in full sun at the end of his driveway.

The incredibly obvious answer is extreme drought, however he claimed to lose one around the same time last year, which was hot and dry, but nothing like our drought this year.

My experience has always been that viburnums are largely pest and disease resistant... are there any exceptions? He describes death as fast moving... is a fungal infection like black spot likely?

Thanks for any theories.