Rhizopus Rot of Jackfruit

THE
 plant genus Artocarpus  comprises roughly 50
species of tropical trees native to the Pacific and
South and Southeast Asia, several of which produce edible fruit. Jackfruit, Artocarpus heterophyllus, is a popular garden species prized for its edible flowers, fruit, and
seeds for fresh consumption or cooking. Jackfruit trees
can reach over 60 ft in height and bear fruit that can be 2
feet or more long and weigh as much as 70 pounds.
Rhizopus rot is a common fungal disease of jackfruit flowers and fruit. Rot is more likely to occur in
high-rainfall areas or during and after stormy periods.
When warm, humid, wet weather coincides with the
flowering and fruiting season, rhizopus rot can cause
total loss of fruit in jackfruit trees.
*
Symptoms
At first, soft, watery, brown spots develop on the flowers and fruit. Subsequently, a powdery, fuzzy-looking
mass of black spores and white fungal mycelia covers
the jackfruit surface. The pathogen engulfs the young
fruit, resulting in the characteristic black, rotten,
shrunken, and sometimes mummified fruit remains. Fruit
symptoms can appear on the tree or can develop on fruit
that are in storage or transit.
Cause
Three species of plant-pathogenic fungi of the genus
Rhizopus can cause this disease in the tropics: Rhizopus
oryzae, Rhizopus artocarpi, and Rhizopus stolonifer. No
Rhizopus Rot of Jackfruit
Scot Nelson
Department of Plant and Environmental Protection Sciences
*According to observations by personnel at the UH-CTAHR Agricultural Diagnostic Service Center.
Left: a healthy, maturing jackfruit; center and right: young jackfruits with rhizopus rot.UH–CTAHR Rhizopus Rot of Jackfruit PD-29 — July 2005
2
jackfruit varieties are reported to have significant resistance to the disease.
Epidemiology
Warm, humid, rainy conditions favor the development
of rhizopus rot. Wind, rain, and insects dislodge and
spread the tiny fungal spores. When deposited on moist
fruit surfaces, the spores germinate and infective mycelia grow into the tissues. The infection produces a layer
of black spores on the fruit surface to start secondary
cycles of infection and disease. Although wounds can
predispose the fruit to infection, unwounded flowers and
young fruit are also susceptible. Rhizopus can survive
on decaying plant litter or in the soil to initiate new infections.
Management
Prune the tree to encourage good ventilation and to reduce relative humidity in the canopy. Remove and destroy diseased fruit from trees and the ground. Clean up
decaying organic debris within and around the tree. Ensure that water does not pond around the tree’s root zone.
Control weeds around young trees. Intercrop jackfruit
with trees that are not susceptible to infection by Rhizopus. Keep ripe fruit from contact with the soil or decaying organic material. Avoid wounding the fruit. Wash
fruit after harvest in clean water and dry thoroughly before packing or transporting. Do not pack fruit with
symptoms—destroy them. Avoid storing fruit after harvest in hot, poorly ventilated containers. Where disease
is severe, protect fruit with periodic sprays of copper
fungicides or other products registered for use on jackfruit in Hawaii.

Diseases
€ Blossom rot, fruit rot or stem rot, all caused by Rhizopus artocarpi, are serious
diseases, which may cause 15 to 32% crop loss.
€ The inflorescence, tips of the flowering shoots or the stalk of the tender fruits are
infected and blackened by fungal structures called sporangia.
€ Flowers and fruits rot and drop.
€ Collect and destroy the fallen leaves and fruits under the tree.
€ On appearance of blossom rot, an application of Folicur or Tilt 250 EC @ 0.5 ml
per litre of water may be sprayed as a further controlling measure.