How to Manage Pests
UC Pest Management Guidelines
Phomopsis Fruit Rot And Branch Dieback
Pathogen: Phomopsis amygdali
(Reviewed 3/09, updated 3/09)
In this Guideline:
SYMPTOMS AND SIGNS
Fruit symptoms of Phomopsis fruit rot include extensive grayish brown discolored and shriveled hulls that often have clear gum secretions and shriveled kernels. Affected fruit frequently abscise. Second-year symptoms include twig and branch dieback (see LOWER LIMB DIEBACK). Leaf lesions are round to irregular in shape with red-brown margins; in later stages they are dry and brown. Lesions are generally isolated but may occur on grouped leaves along a branch. Leaf lesions may abscise causing a shot hole symptom.
COMMENTS ON THE DISEASE
The disease is uncommon under California growing conditions and has only occasionally been reported in late spring and early summer when unusual high rainfall occurs in mid- to late spring. Sonora and Carmel are very susceptible; whereas Nonpareil and Mission are less susceptible to the disease.
Generally, chemical control measures are not needed. If necessary, make one to two applications of Captan before late spring rains. Cultural control practices are ineffective.
UC IPM Pest Management Guidelines:
J. E. Adaskaveg, Plant Pathology, UC Riverside