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Anthracnose of Pomegranate

Anthracnose of Pomegranate

Glomerella cingulata

fungi

In a Nutshell

    Minute dull violet to black spots on plant tissues surrounded by a yellow haloThe spots later enlarge to cover whole leaves which finally shed prematurelyDry, reddish brown to black discoloration on fruits, often starting from the lower partThe fruit later softens and starts to rotAffected twigs, branches or trunks can occasionally result in girdling and dieback

Hosts: %1$s

· Pomegranate

Symptoms

The fungus causes a wide range of symptoms, depending the tissue attacked and the weather. Minute sunken spots of various colors appear on leaves, stems, flowers or fruits, often surrounded by a more or less marked yellow halo. On leaves, the spots later enlarge to form lesions and can cover a major part of the blades. They turn yellow and can shed prematurely leading to defoliation. Spots on fruits are brown to dark brown, first circular, then irregular as they expand. The fruit later softens and rot develops in the arils which turn dark gray or black but are not watery. Anthracnose also can attack twigs and branches and results in cankers, which are areas of sunken, infected tissue with swollen edges. The infection of the trunk can occasionally result in girdling and dieback.

Trigger

The symptoms are caused by the fungus Glomerella cingulata. It overwinters in infected plant residues on the soil surface or in mummified fruits. In spring its spores are spread via rain splashes or wind and infect neighboring twigs or plants. The most susceptible stages are the bloom and fruit development period. Injuries due to the tree thorns, insect, and animals favor the infection process. Frequent rainfall, a high humidity (50-80%) and a temperature range of 25-30°C favor the life cycle of the fungus. However, it is usually inactive in dry season. Even light infections can cause cosmetic damage to the fruit and shorten its storage life. Other hosts are for example Mango, Guava, and Papaya.

Biological Control

Known biocontrol agents are competitive fungi Aspergillus flavus, Hypocrea rufa, Hyponectria tuberculariformis and Nectriella muelleri. Only the first one is a real antagonist. The others are parasites or pathogens.

Chemical Control

Always consider an integrated approach with preventive measures together with biological treatments if available. A first preventive spray could be applied when flowering begins and the environmental conditions are favorable for the fungus. Then spray at 15 days interval twice, if necessary. Active ingredients are propiconazole, mancozeb, carbendazim or a combination of mancozeb and carbendazim or tricyclazole. Only spray fungicides with an actual registration for pomegranate. It is important to follow the specified concentrations and to use fungicides with different mode of actions to prevent resistances.

Preventive Measures

    Use healthy plant material from certified sourcesUse tolerant varieties available in your areaKeep sufficient space between the plants to ensure good ventilationProvide a good drainage to the fields and do not use overhead irrigationFertilize after the leaves are open and the spring rains have stoppedFertilize your crop properly to avoid impact on yieldEnsure a good field hygiene, with weed control for exampleAvoid mechanical or physiological damage of the plantCheck your plants or fields for any sign of disease, especially during bloom and fruit development periodPrune during winter and sterilize the pruning toolsRake and remove fallen leaves and infected twigs and branches during the growing season and in fall