How to Manage Pests

UC Pest Management Guidelines

SYMPTOMS (View photos)

Decay from stem end rot begins as slight shriveling around the stem button. Fungal mycelium are often visible on fruit if the button is removed. Conspicuous dark decay with a well-defined margin develops at the stem end. As fruit ripens, decay spreads and rots the entire fruit, which becomes dark and shriveled. Depending on the causal organisms, flesh may be watery and soft, or initially dry and corky, becoming watery later as secondary organisms colonize tissue.

COMMENTS ON THE DISEASE

Decay at the stem end of fruit is caused by the several species of bacteria and fungi. Causes include the fungus Botryodiplodia theobromae and other fungi discussed in ANTHRACNOSE and DOTHIORELLA FRUIT ROT, as well as Alternaria and Phomopsis spp. These stem end rotting species are saprophytes (decay organisms) or weak pathogens, which are present in soil and most any dead or dying avocado tissue, including senescing flowers and injured bark, fruit, and leaves. Spores spread in wind and splashing water.

Stem end rot infection typically occurs in the grove during harvest, but does not develop into disease until after fruit is shipped to the packinghouse. Harvesting injures fruit around the button, and bacteria and fungi can enter the freshly cut stem, causing decay as fruit ripens.

MANAGEMENT

Use good sanitation and optimal cultural practices to minimize fruit rots. Prune out dead limbs and twigs. Dispose of dead wood and old fruit away from trees. Prune and harvest only during dry conditions. Correct environmental and nutritional stresses. Minimize other diseases and disorders that injure bark, fruit, or leaves. Provide sufficient irrigation with appropriate placement of high quality water. Maintain a thick layer of mulch under canopies to hasten decomposition of pathogen propagules. Do not harvest during or soon after rain; allow trees and fruit to dry before harvesting. Minimize the interval from harvest until fruit is placed into cold storage at the packing house; prompt cold storage reduces disease incidence. Follow the same postharvest handling instructions discussed in ANTHRACNOSE.

PUBLICATION

UC IPM Pest Management Guidelines: Avocado
UC ANR Publication 3436
Diseases
B. A. Faber, UC Cooperative Extension, Santa Barbara/Ventura counties
G. S. Bender, UC Cooperative Extension, San Diego County
H. D. Ohr (emeritus), Plant Pathology, UC Riverside
Acknowledgment for contributions to the diseases section:
L. J. Marais, Plant Pathology, UC Davis
J. A. Menge, Plant Pathology, UC Riverside
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

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