How to Manage Pests
UC Pest Management Guidelines
Fruit and Stem-end Rots
Pathogen: Fungal species in the Botryosphaeriaceae and Colletotrichum spp.
(Reviewed 9/16, updated 9/16)
In this Guideline:
SYMPTOMS AND SIGNS (View photos to identify causes of fruit damage)
Avocado fruit and stem-end rots are usually not obvious while fruit is on the tree. Small, superficial lesions can develop on fruit in the grove, but the disease usually is apparent only on fruit that is very overmature, hanging on dead limbs or dropped on the ground.
Infections usually become active after the fruit is picked and starts to soften. Initially lesions are small, irregular brown to reddish discolorations on the peel. Under the peel, brown streaks running lengthwise in the flesh may be observed because decay initially spreads along vascular bundles in the fruit. Small, purplish brown spots may appear on any part of the fruit, most often at the stem end. As fruit ages, the surface lesions gradually enlarge and become sunken and black. Fruit shrivels, and the black surface can become covered with grayish brown fungal mycelium and spores. Decay then spreads throughout the entire fruit, causing the flesh to turn brown and watery, with an offensive odor.
COMMENTS ON THE DISEASE
Postharvest rots are a relatively minor problem of avocados in California. Avocado fruit rot is caused by several Botryosphaeriaceae genera and species. The same group of fungi can cause avocado branch canker and dieback.
These pathogens spread by wind-blown or water-splashed spores produced in or on cankers, dead twigs and branches, and dying fruit and leaves. Spores infect through wounds and lenticels (tiny natural openings) on fruit. Infection occurs in the grove, but disease usually is not obvious until after fruit is picked and starts to ripen.
Damage from avocado fruit rot closely resembles that from ANTHRACNOSE and fruit damaged by these pathogens are usually culled and lumped together in the packing house. Anthracnose produces pink sporulation on the fruit surface, in contrast with the grayish mycelium from avocado fruit rot.
Use good sanitation and optimal cultural practices to minimize avocado fruit rot.
UC IPM Pest Management Guidelines:
A. Eskalen, Plant Pathology, UC Riverside
Acknowledgment for contributions to Diseases:G. S. Bender, UC Cooperative Extension, San Diego County
H. D. Ohr (emeritus), Plant Pathology, UC Riverside
J. A. Menge, Plant Pathology, UC Riverside
L. J. Marais, Plant Pathology, UC Davis
R. Hofshi, Hofshi Foundation, Fallbrook, CA
J. S. Semancik, Plant Pathology, UC Riverside
J. A. Downer, UC Cooperative Extension, Ventura County
U. C. Kodira, Plant Pathology, UC Davis