Symptoms and Signs
Trees affected by almond kernel shrivel bloom later than healthy trees, new shoot growth is stunted, and leaves are pale and smaller than normal. Trees develop thin canopies and the kernels of all nuts are shriveled at harvest.
Comments on the Disease
Almond kernel shrivel has occurred in certain locations of the northern San Joaquin Valley on almond trees planted on peach rootstock. It is caused by the Peach yellow leafroll phytoplasma and is known to affect almond scions grown on peach rootstock. Peach yellow leafroll phytoplasma can be transmitted by certain insect vectors, and it is presumed that diseased almond trees are infected in this manner. The phytoplasma can also be transmitted in infected budwood.
Management
At the present time, the only management recommendations for almond kernel shrivel are to remove diseased trees and use planting material produced using budwood sources known to be free of the pathogen.