Water Melon Diseases A

Lecture To ToT trainees ( FFS) By

Mr. Allah Dad Khan Provincial Coordinator

IPM KPK MINFAL Pakistan

Root knot nematodeMeloidogyne spp.

Symptoms

Galls on roots which can be up to 3.3 cm (1 in) in diameter but are usually smaller; reduction in plant vigor; yellowing plants which wilt in hot weather

CauseNematode

Southern blight (Stem and fruit rot)Sclerotium rolfsiiSymptoms

Sudden wilting of leaves; yellowing foliage; browning stem above and below soil; browning branches; stem may be covered with fan-like mycelial mat

CauseFungus

Fusarium wiltFusarium oxysporum

Symptoms Yellowing and wilting of runners;

lesions on the runner extend from crown to tips; lesions on roots and stems; internal red to brown discoloration

Cause Fungus Comments Disease emergence favored by

warm, wet soil Management Plant in well draining soils and

avoid waterlogging; plant fungicide treated seed; rotate crops on 4 year rotation

Gummy stem blightDidymella bryoniaeSymptoms

Circular brown or tan spots of various sizes on leaves; leaves covered with lesions; stems splitting and forming cankers; wounds exude a brown, gummy substance; wilting vines; death of stems; small water-soaked lesions on fruit which enlarge and exude gummy subatnace; black fruiting bodies often present in lesions

CauseFungus

Anthracnose (Leaf spot, Fruit rot)Colletotrichum orbiculare symptoms

Lesions on fruit and leaves which may develop salmon pink spore masses during periods of wet weather

Cause FungusComments Favors wet conditionsManagement Rotate crops with non-cucurbits

every 1-2 years to prevent disease build-up; plant only disease free, treated seed

Alternaria leaf spotAlternaria spp. Symptoms

Irregularly shaped or circular dark brown lesions on leaves; lesions may occur in concentric circles

CauseFungus

Charcoal rotMacrophomina phaseolinaSymptoms

yellowing, dying leaves; water-soaked lesion on stem at soil line; stems oozing amber gummy substance; stem drying and turning tan brown in color; lesion may girdle stem and kill plant;

CauseFungus

Downy mildewPseudoperonospora cubensisSymptoms

Dead or dying leaves; yellow to brown lesions on the upper side of leaves; purple growth developing on the underside of leaves

CauseFungus

Watermelon mosaicWatermelon mosaic virus (WMV)

Symptoms

Symptoms vary widely depending on species, cultivar, virus strain and environmental conditions; symptoms on leaves may include green mosaic patternation, green vein-banding, chlorotic rings and disfigured leaves

CauseVirus

Zucchini yellow mosaicZucchini yellow mosaic virus (ZYMV)

Symptoms

Infected plants are severely stunted and leaves can exhibit a variety of symptoms including yellow mosaic patternation, severe deformation, blistering, reduced size and necrosis; fruits are deformed

CauseVirus

Monosporascus vine decline

Monosporascus cannonballusSymptoms

Leaves turning chlorotic; sudden collapse of plant canopy 1-2 weeks before harvest; root lesions generally become evident several days after plant death; lesions become covered in black dots (fungal fruiting bodies)

CauseFungus

Powdery mildewPodosphaera xanthiiErysiphe cichoracearumSymptoms

White powdery growth on the upper surfaces of leaves and stems; infected areas stunted and distorted

CauseFungus

Squash mosaicSquash mosaic virus (SqMV)

Symptoms

Symptoms vary with variety being grown but plants can show symptoms which include include green veinbanding, mottled leaves, blisters, ring spots or potruding veins at leaf margins; some squash varieties may develop leaf enations; infected plants are often stunted and fruits may be malformed with mottled skin

CauseVirus

Angular leaf spotPseudomonas syringaeSymptoms

Small water-soaked lesions on leaves which expand between leaf veins and become angular in shape; in humid conditions, lesions exude a milky substance which dries to form a white crust on or beside lesions; as the disease progresses, lesions turn tan and may have yellow/green edges; the centers of the lesions dry and may drop out leaving a hole in the leaf

CauseBacterium

Bacterial wiltErwinia tracheiphilaSymptoms

Wilting of individual runners or entire plant; leaves and stems of affected parts turn dark green; wilting is irreversible; affected parts turn necrotic

CauseBacterium

Cucumber mosaicCucumber mosaic virus (CMV)Symptoms

Plants are severely stunted; foliage is covered in distinctive yellow mosaic; leaves of plant curl downwards and leaf size is smaller than normal; flowers on infected plants may be deformed with green petals; fruits become distorted and are small in size; fruit is often discolored

CauseViruses

Verticillium wiltVerticillium dahliae

Symptoms

Symptoms generally appear after fruit set; chlorotic leaves which develop necrotic areas; leaves collapsing; symptoms only on one side of vine; discoloration of vascular tissue in roots

CauseFungus

Fusarium Wilt (Fusarium oxysporum f. sp. niveum)

 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.

Symptoms:

Alternaria leaf blightAlternaria cucumerina

Symptoms

Small, yellow-brown spots with a yellow or green halo which first appear on the oldest leaves; as the disease progresses, lesions expand and becone large necrotic patches, often with concentric patternation; lesions coalesce, leaves begin to curl and eventually die

CauseFungus

Cercospora leaf spotCercospora citrullina

Symptoms

Initial symptoms of disease occur on older leaves as small spots with light to tan brown centers; as the disease progresses, the lesions enlarge to cover large areas of the leaf surface; lesions may have a dark border and be surrounded by a chlorotic area; the centers of the lesions may become brittle and crack

CauseFungus

Septoria leaf spotSeptoria cucurbitacearum

Symptoms

Initial symptoms of disease are small dark water-soaked spots on the leaves which turn beige to white in dry conditions; lesions develop thin brown borders and the centers may become brittle and crack; small white spots may erupt on the surface of infected butternut and acorn squash and pumpkin fruit

CauseFungus