How to Manage Pests

UC Pest Management Guidelines

Symptoms of Pilidiella fruit rot on pomegranate, caused by Pilidiella granati.

Pomegranate

Pilidiella Stem Canker and Fruit Rot

Pathogen: Pilidiella granati

(Reviewed 10/13, updated 10/13)

In this Guideline:


Symptoms and signs

Pilidiella granati causes stem and crown cankers, resulting in decline and eventual death of young pomegranate shoots. Fruit decay may occur in the field and postharvest.

Infection turns the arils brown and juicy. Fruit membranes and the rind also turn brown. Black fungal pycnidia with characteristic large, elliptical, colorless, one-celled spores can develop on the surface of the arils, membranes, and surface of the rind (fruit skin). Pycnidia can also be found in the bark of trunks, killed shoots, and thorns, as well as on the surface of leaves. Infected fruit left in the orchard are called mummies.

Pilidiella rot is very different from Alternaria fruit rot, Aspergillus fruit rot, and gray mold.

Pilidiella stem canker and fruit rot Alternaria fruit rot
(Alternaria alternata and other Alternaria spp.)
Aspergillus fruit rot
(Aspergillus niger)
Gray mold
(Botrytis cinerea)
Decay of fruit rind and arils Decay of fruit rind in later stages of infection; arils decay: brown decay and black sporulation inside fruit Decay of fruit rind; arils decay: brown decay and black sporulation inside fruit Decay of fruit rind and arils; grayish mycelium
Pycnidia on trunk, shoots, thorns, leaves, and fruit No symptoms or signs on trunk, shoots, thorns, and leaves No symptoms or signs on trunk, shoots, thorns, and leaves Sporulates on decayed fruit, killed shoots, thorns, and leaves

Comments on the disease

The pathogen is isolated frequently from pomegranates, but the disease is only sporadically found in Fresno, Madera, and Kern county orchards.

In orchards, the pathogen overwinters as pycnidia and mycelia in stem cankers and rotten fruit (mummies), tree prunings, and desiccated leaves.

Fruit infection occurs through wounds (e.g., insect exit holes, bird pecks, thorn punctures, and natural cracking). Infections, however, can spread by contact from infected fruit to healthy fruit in packed boxes, similar to gray mold.

The optimum temperature for the pathogen's growth ranges from 25 to 30°C; the fungus grows slowly at 15°C, but not at 35°C.

Losses from Pillidiella rot have not been estimated, since this is a new disease of pomegranate in California.

Management

Sanitation may reduce overwintering inoculum. Remove or burn pruned limbs and bury mummies.

PUBLICATION

[UC Peer Reviewed]

UC IPM Pest Management Guidelines: Pomegranate
UC ANR Publication 3474

Diseases

  • J. E. Adaskaveg, Plant Pathology, UC Riverside
  • T. J. Michailides, Kearney Agricultural Center, Parlier

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