A disease that is little more than a curiosity on some plants but sometimes causes damage to almond trees has now been found on citrus. Its name is 'foamy canker of almond' or 'foamy bark rot of citrus', and among plant diseases, has some of the most memorable and distinctive symptoms.
Foamy bark rot better describes the symptoms observed on citrus.
It was first seen on almond trees, and in the early 1980's was found in numerous orchards, especially in the central and southern San Joaquin Valley. At that time, the disease seemed to be restricted to two-year old 'Carmel' almonds. Since then, almond trees of all ages and many cultivars have been included as hosts and the host list has expanded to include apricot, peach, mulberry, elm, pittosporum, longbean, and now, citrus. The disease has been seen on citrus in previous years, and on other cultivars, but never in sufficient number to cause alarm. Foamy canker of almond makes its entrance sometime in mid to late summer and after a spate of hot weather.