White powder covering a canker of branch canker and dieback, formerly called Dothiorella canker. The disease is caused by Phomopsis (=Diaporthe) species and various fungi in the Botryosphaeriaceae family.

White crystalline exudate and dark bark around main branch junction with trunk on avocado infected with Dothiorella canker. San Diego Co.   Credit: David Rosen
Credit: David Rosen