Lettuce Diseases A

Lecture To ToT trainees ( FFS) By

Mr. Allah Dad Khan Provincial Coordinator

IPM KPK MINFAL Pakistan

AnthracnoseColletotrichum higginisianum

Symptoms

• Small circular or irregularly shaped dry spots which are gray to straw in color on leaves; a high number of spots may cause the leaf to die; lesions may coalesce to form large necrotic patches causing leaves to turn yellow and wilt; lesions may split or crack in dry centers; dry sunken spots on roots which enlarge and turn gray or brown

• Cause• Fungus

Alternaria leaf spot (Black spot, Gray spot)Alternaria spp.

Symptoms

• Small dark spots on leaves which turn brown to gray; lesions may be round or angular and may possess a purple-black margin; lesions may form concentric rings, become brittle and crack in center; dark brown elongated lesions may develop on stems and petioles

• Cause• Fungus

Cercospora leaf spot (Frogeye leaf spot)Cercospora brassicicola

Symptoms

• Angular or circular green to gray spots with brown borders on leaves; plant defoliation may occur in the case of a severe infestation

• Cause• Fungus

Downy mildewPeronospora parasitica

Symptoms

• Irregular yellow patches on leaves which turn light brown in color; fluffy gray growth on the undersides of the leaves

• Cause• Fungus

White spotPseudocercosporella capsellae

Symptoms

• Small, necrotic, brown spots on leaf tips or margins that matures to light gray or white with the original dark spot in center; margins of lesions may be darker; lesions may coalesce to form large chlorotic areas and cause defoliation

• Cause• Fungus

Sclerotinia rot (White mold)Sclerotinia sclerotiorum

Symptoms

• Irregular, necrotic gray lesions on leaves; white-gray leions on stems; reduced pod set; shattering seed pods

• Cause• Fungus

ClubrootPlasmodiophora brassicae

Symptoms

• Slow growing, stunted plants; yellowish leaves which wilt during day and rejuvenate in part at night; swollen, distorted roots; extensive gall formation

• Cause• Fungus

Black rootAphanomyces raphari

Symptoms

• Small black-blue areas on roots which expand and girdle taproot; roots become constricted at site of lesions; black discoloration extends into root

• Cause• Fungus• Comments• Fungus can survive in soil for

prolonged periods• Management• Control depends on crop rotation

with non-brassica species

Wirestem (Damping-off)Rhizoctonia solani

Symptoms

• Death of seedlings after germination; brown-red or black rot girdling stem; seedling may remain upright but stem is constricted and twisted (wirestem)

• Cause• Fungus

Black rotXanthomonas campestris

Symptoms

• Seedlings develop wilted yellow to brown leaves and collapse; yellow, V-shaped lesions on mature leaf margins; dark rings can be found in the cross section of the stem

• Cause• Bacterium

Turnip mosaicTurnip mosaic virus (TuMV)

Symptoms

• Yellow and green mosaic patterns on leaves; necrotic areas on leaves; veinclearing and chlorosis may occur in older leaves; black spots and brown necrotic streaks on stems; stunted plant growth ond reduced yield

• Cause• Virus

White rust lbugo candida

Symptoms

• White pustules on cotyledons, leaves, stems and/or flowers which coalesce to form large areas of infection; leaves may roll and thicken

• Cause• Fungus