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.
Management
Cultural control practices are ineffective. Fungicide applications in mid-spring may be beneficial.
| Common name | Amount per acre | REI‡ | PHI‡ | |
|---|---|---|---|---|
| (Example trade name) | (hours) | (days) | ||
| Not all registered pesticides are listed. The following are ranked with the pesticides having the greatest IPM value listed first—the most effective and least likely to cause resistance are at the top of the table. When choosing a pesticide, consider information relating to the pesticide's properties and application timing, honey bees, and environmental impact. Always read the label of the product being used. | ||||
| A. | CAPTAN | |||
| (various 50WP) | 8 lb | 24 | See label | |
| MODE-OF-ACTION GROUP NAME (NUMBER1): multi-site contact (M4) | ||||
| COMMENTS: Make one to two applications of Captan before late spring rains to prevent fruit rot. Do not apply in combination with, immediately before, or closely following oil sprays. | ||||
| ‡ | Restricted entry interval (REI) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without protective clothing. Preharvest interval (PHI) is the number of days from treatment to harvest. In some cases the REI exceeds the PHI. The longer of these two intervals is the minimum time that must elapse before harvest may occur. |
| 1 | Group numbers are assigned by the Fungicide Resistance Action Committee (FRAC) according to different modes of action. Fungicides with a different group number are suitable to alternate in a resistance management program. In California, make no more than one application of fungicides with mode-of-action group numbers 1, 4, 9, 11, or 17 before rotating to a fungicide with a different mode-of-action group number; for fungicides with other group numbers, make no more than two consecutive applications before rotating to a fungicide with a different mode-of-action group number. |