Sunday, April 17, 2011

Diseases

/bitter melonPowdery Mildew (Sphaerotheca fuliginea) :
This disease is favored by high humidity and tends to occur on older leaves first. Symptoms first
appear as white powdery residue primarily on the upper leaf surface. On the lower surface of the
leaves circular patches or spots appear. In severe cases, these spread, coalesce and cover both
the surfaces of the leaves and spread also to the petioles, stem, etc. Severely attacked leaves
become brown and shrivelled and defoliation may occur. Fruits of the affected plants do not
develop fully and remain small.

Control: Carbendazim (1ml/litre of water) or Karathane (0.5 ml/litre of water) is sprayed immediately
after the appearance of the disease. 2-3 sprays are taken at an interval of 15 days.

Fusarium Wilt (Fusarium oxysporum f. sp. niveum) :
Initially the plants show temporary wilting symptoms, which becomes permanent and progressive,
affecting more vines. The leaves of the affected plants show yellowing, loose turgidity and show
drooping symptoms. Eventually, the plant dies. The roots are not affected. In older plants, leaves wilt
suddenly and vascular bundles in the collar region become yellow or brown.
Control: Three sprays of Karathane (6 g in 10 litres of water) or Bavistin (1 g /litre of water) immediately
on appearance of initial symptoms at 5-6 days interval controls the disease. Leaves of fully grown
vines should be thoroughly drenched during spraying.
Downey Mildew (Pseudoperonospora cubensis) :
It is prevalent in areas of high humidity, especially when summer rains occur regularly. The disease is
first seen as yellow angular spots on the upper surface of the leaves. Under conditions of high humidity,
whitish powdery growth appears on the lower surface of the leaves. The disease spreads rapidly killing
the plant quickly through rapid defoliation.

Control: Excellent control of this disease can be achieved with Ridomil (1.5 g/litre of water) which must
always be used simultaneously with a protectant fungicide such as Mancozeb (0.2%) to prevent the
development of resistant strains.

Bitter Gourd Mosaic :
This virus disease is mostly confined to the leaves with symptoms appearing on the leaves in the
secondary branches produced at the apical end of the plant. Small irregular yellowish patches are
seen on the leaves. Some leaves show vein clearing in one or two lobes of the leaf and severely
infected plants show reduction in leaf size and elongation and/or suppression of one or two lobes.
Young developing leaves are completely distorted and malformed with considerable reduction in their
size. Some of the leaves show marked reduction in the development of lamina resulting in a shoestring
effect. The virus is transmitted by five species of aphids.

Control: Spraying the crop just after germination with Monocrotophos (0.05%) or Phosphamidon
(0.05%) at 10-day intervals prevents aphid vectors.

Bitter gourd Witches' Broom :
Plants infected in the early stages do not bear any fruit and the loss is 100%. Characteristic symptoms
of this disease are malformation and proliferation of axillary buds. Diseased plants show many
abnormally little leaves, which fail to attain full size. The diseased plants bear many flowers and
blossom earlier than healthy plants. Flowers on infected plants show characteristic green, phyllody
symptoms. Fruit formation is noticed from the flowers partially infected with the disease. Fruits from
these flowers are very small, cylindrical and deformed. The outer surface of the fruits is smooth and
fruits are completely seedless. Plants showing severe witches' broom do not bear any fruit.

Control: Application of Carbofuran (1.5 kg a.i./ha) at the time of sowing seeds followed by 5-6
foliar sprays of either Phosphamidon (0.05%) or Monocrotophos (0.05%) or Oxydematon Methyl
(0.05%) at 10 days interval, to control the vector population. Spraying of Oxytetracycline
hydrochloride solution (500 ppm) at weekly intervals suppress the disease symptoms

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