Diseases Of Cucurbits

By TamilNadu Agricultural University on 27 May 2016 | read
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Diseases of Cucurbits

Fusarium wilt of water melon  (Fusarium oxysporum f. sp. Niveum), Muskmelon – F. o. fsp. Melonis         
Symptoms

The disease attack the plant at all stages of plant growth. When young seedlings are infected they damp off and die. In older plants the plant wilt and die within 10 days. Vascular discolaration can be seen. In wet weather, pinkish or whitish fungal growth can be seen on dead stems.

Mangement

Collection and burning of infected plant. Seed treatment and soil application with T. Viride or P. fluorescens Use of disease free seeds.

Root rot of muskmelon (Pythium aphendermatum)

 Root rot of pumpkin and squash (Fusarium solani f.sp. cucurbitae)

 Root rot of watermelon, cucumber (Pythium irregulare and P.ultimum)

Symptoms

The roots of the affected plants appear water soaked with sunken darkened lesions. The crown of the plants is girdled and entire plant is collapsed. Fruits become rotted by the fungus.

Management

As like wilt the management practice should be followed.

Verticillium wilt  (Verticillium albo-atrum)

Symptoms

The leaves of the plant become yellow from base of the plant upwards and the whole plant wilts. If the stem is cut open, brown discoloration can be seen.

Anthracnose (Collectorichum lagenarium)

Symptoms

Small yellowish or water soaked areas appears on leaves which enlarge rapidly and turn brown in most cucurbits but black in water melon. The affected bart break and fall of or the whole leaf dries. When the infection occurs in stem, the whole vine is killed. When infection occurs in fruit pedicle, the young fruit may be darken, shrivel and dry. Circular black  cankers appear on fruits. The spots may be up to 5 cm dia based on the host and environment. In the sunken black spots salmon coloured spores can be seen.

Management

Collection and destruction of infected plant.

Alternaria leaf spot/ target leaf spot / Macrosporium blight (Alternaria cucumerina, Macrosporium cucumerinum)

Symptoms

Small, circular spots appear on leaves. As the spot enlarges concentric rings can be seen on infected area. The fungus also causes fruit rot

Management

Use of disease free seeds.

Cercospora leaf spot (Cercospora citrullina)

Symptoms

Small block circular spots with grey centre appear on leaves. Severely infected leaves fall off. The fruit size is reduced.

Management

Collection and burning of infected leaf. Crop rotation.

Downy mildew (Pseudoperonospora cubensis)

Symptoms

Symptoms resembling mosaic viz, pale green areas separated by dark green areas appear on upper surface of leaf. During wet season, corresponding lower surface is covered with faint purplish fungal growth. The entire leaf dries up quickly.

Management

Use of bed system with wide spacing with good drainage and air movement and exposure to sun help to check the disease development.

Angular leaf spot (Pseudomonas syringae pv.lachrymans)

Symptoms

Water soaked lesions appear on leaves which are confined to veins. The turn grey to tan and form an exudates in the lower surface. The spots loosen and fall out. Infected fruits develop a brown, circular, superficial, firm rot which causes rapid detorition. The rot may extend into flesh.

Management

Use of disease free seed and crop rotation.

Fruit rot (Pythium aphenidermatum)

Symptoms

Initially the skin of the fruit shows soft, dark green water soaked lesions which gradually develop into a watery soft rot. Cottony mycelium develop on the affected portions. The fruit in contract with the soil is attacked easily.

Management

Keep fruits not in touch with soil

Other fruit rots of watermelon

Apergillus fruit rot – Aspergillus flavus Curvularia fruit rot – Curvularia ovoidae Myrothecium fruit rot – Myrothecium roridum Rhizopus fruit rot – Rhizopus oryzae Diplodia fruit rot – Diplodia natalensis (also affects cucumber)

Viral disease

Cucumber mosaic virus – Vector- aphids (A. craccivora M.persicae)

Symptoms

Mosaic mottling, leaf distortion, stunting of the plants, shortened internode and petoles. Infected plants bear only very few flowers. In fruits mottled yellowish green areas can be seen.

Management

Removal and burning of infected plants. Eradication weeds hosts

Other viral diseases

Watermelon mosaic virus – watermelon and muskmelon Squash mosaic – Squash and pumpkin Mosaic disease – Bottle gourd, snake gourd, squash, ribbed gourd

Management

Removal and burning of infected plants. Eradication weeds hosts

Phyllody – Phytoplasma (Vector – leaf hopper)

It affects bitter gourd, bottle gourd, cucumber, ridge gourd and snake gourd. The symptoms are shortening of internodes and phyllody of normal flowers. Corolla, androecium and gynecium are transferred into green leaf like structures.

Management

Removal of infected plants. Clean cultivation without weed host.



 

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