DISEASES OF CLOVE

DISEASES OF CLOVE

Clove (Eugenia caryophyllus (Spreng.) Bullock & S.G. Harrison) popularly known as Laung belongs to family Myrtaceae is an air dried , unopened flower bud obtained from a medium sized, evergreen, straight trunked tree that grows in Kerala and Tamil Nadu. The term “clove” is derived from the French word ‘Clov’ and the English word ‘clout’ both meaning ‘nail’ from the likeness of the flower bud of the clove tree to a broad headed nail. In India, clove was introduced in 1800 by the East India Company. During cultivation the trees are affected by several diseases which cause significant yield reductions. In this lecture, important diseases along with their management practices are described.

1. LEAF SPOT, TWIG BLIGHT AND FLOWER SHEDDING
The disease was reported from Kerala and when the flowers are seriously affected there is heavy shedding and the losses are huge.

Symptoms:
  • The symptoms of the disease appear as small, circular to oval-brown scattered specks on the leaf lamina.
  • These specks gradually enlarge and develop into distinct spots having ashy-gray centres and darker margins.
  • Several spots coalesce together leading to the formation of necrotic patches.
  • Later the infection proceeds to petiole resulting in defoliation.
  • On young twigs, isolated brown dots appear which coalesce to form large necrotic areas and lead to die-back symptoms with eventual death of the twigs.
  • On flowers, black buds appear, pedicels shrivel and are killed.
  • In heavy and continuous rainfall, profuse shedding of flowers occurs.
  • Whitish growth of the fungus can be seen in fallen flower buds.
Pathogen:
  • The disease is caused by Colletotrichum gloeosporioides (Penz.) Penz. & Sacc.
  • The mycelium is grayish white, thin and sparsely septate.
  • Acervuli are glabrous, rounded and elongated or irregular in shape with setae.
  • Conidia are cylindrical with obtuse ends, one celled and are formed on aseptate, hyaline or faintly brown cylindrical phialidic conidiophores.
Disease cycle and epidemiology:
  • The organism has a wide host range and the infection is by air-borne conidia.
  • Heavy and continuous rainfall favour the infection and disease spread.
Management
i) Destroy weed, Clerodendron growing in clove gardens as it serves as the collateral host.
ii) With the initiation of the disease spray the crop with Bordeaux mixture (4:4:50) or mancozeb (0.25%) and repeat at 14 days interval particularly in rainy season.


2. SUDDEN DEATH
It is a one of the serious disease of clove.

Symptoms:
  • On mature trees, slight chlorosis occurs on the leaves which results in a sudden and rapid leaf fall followed by wilting of the plants.
  • Complete death of the plants occurs within a few days.
  • The roots are also affected by the pathogen.
Pathogen:
  • The disease is caused by Valsa eugeniae Nutman & Roberts.
  • The perithecia are produced in large numbers.
  • The ascospores are formed during the rainy season and are washed down to the soil where they infect the roots.

3. LITTLE LEAF
Symptoms:
  • The affected trees exhibit symptoms of complete repression.
  • The trunk shows numerous protuberances.
  • The branches grow at acute angles with the trunk giving a cone-shaped appearance to the tree.
  • Leaves are reduced in size, internodes are short and primary and secondary branches are arranged closer to each other.
  • The disease also affects seedlings in the nursery.
  • Presence of short internodes and clustering of small, crinckled leaves is also observed.
Pathogen: The disease is caused by Phytoplasma.

Management: The disease can be kept under check by spraying tetracycline.

Other diseases of importance are:
i. Die-back : Cryptosporella eugeniae Nutman & Roberts.
ii. Sumatra or die-back : Endothia sp., Phymatotichum sp. and Phytophthora sp
iii. Leaf blight : Cylindrocladium quinquiseptatu Boedijn & Reitsma
Last modified: Friday, 2 March 2012, 5:52 AM