Leaf spot, twig blight and flower bud shedding (Colletotrichum gloeosporioides)
Three types of symptoms are seen viz., leaf spot, twig blight and flower bud shedding. On the leaves, necrotic spots of variable sizes and shapes are noticed. Severely affected leaves wither, droop and dry up. In the nursery seedlings, dieback symptoms are seen. Extension of the symptoms from the leaves through petioles results in the infection of twigs. The affected branches stand without leaves or only with young leaves at the tips. The flower buds are attacked by spread of infection from the twigs. Shedding of flower buds occurs during periods of heavy and continuous rainfall.
Control
Spraying 1% Bordeaux mixture at 1-1 1/2 month intervals reduces disease intensity, defoliation and flower bud shedding. The spraying has to be commenced just prior to flower bud formation and continued till the harvest of flower buds for effective control. Destruction of the weed Clerodendron from the clove garden is recommended to reduce the disease since the pathogen survives on this weed during adverse conditions.
Seedling wilt- (Cylindrocladium sp., Fusarium sp. and Rhizoctonia sp.)
Seedling wilt is a serious problem in majority of the nurseries and causes 5-40 % death of seedlings. The leaves of affected seedlings lose natural lustre, tend to droop and ultimately die. The root system and collar region of the seedling show varying degrees of discoloration and decay.
Control
The foliage may be sprayed with Bordeaux mixture 1% and the soil drenched with copper oxychloride 0.2%.Since the infected plants promote further spread of the disease, they are to be removed and the remaining seedlings should be treated with carbendazim 0.1% both as spray and soil drench.
Leaf rot (Cylindrocladium quinqueseptatum)
The infection starts as dark diffuse patches at the leaf tip or margin and later the whole leaf rot resulting in severe defoliation.
Control
The foliage of affected trees should be sprayed with carbendazim 0.1%. Prophylatic sprays with Bordeaux mixture 1% also prevents the disease.
Leaf spots and bud shedding
The disease is characterized by the appearance of dark brown spots with a yellow halo on leaves and such spots also appear on the buds resulting in their shedding.
Control
Prophylatic spraying with Bordeaux mixture 1% prevents both the diseases.