Plant diseases caused byBacteria

1 .Spots and Blights

4 .Vascular wilts2 .Soft rots

3 .Galls 6 .Canker and Gummosis5 .Scabs

Wild fire Spot Speck

wilt Fire blightBlack rot

Canker and GummosisCanker

1.Bacterial spots and blights

a- Wildfire of tobaccoDisease name: Wildfire Plant: Tobacco (Nicotiana tabacum L.)Pathogen: Pseudomonas syringae

Symptoms:

Round spots: brown in centers and whitish yellow halos

Adjacent spots coalesce → large dead area on the leaf

b- Bacterial spot of tomato and pepper

Disease name: Bacterial spotPlant: Tomato, PepperPathogen: Xanthomonas campestris

Symptoms:

Tomato

On unripe fruits: small water soaked, slightly raised spots.

spots sometimes have greenish-white halos → dark brown with scabby surface.

Pepper

On unripe fruits: small water soaked, slightly raised spots.

spots sometimes have greenish-white halos → dark brown with scabby surface.

c- Bacterial speck of tomato

Disease name: Bacterial SpeckPlant: TomatoPathogen: Pseudomonas syringae

Symptoms:

Lesions are similar to bacterial spot but smaller

2.Bacterial vascular wilts

a- Bacterial wilt of cucurbitsDisease name: Bacterial wilt Plant: Cucurbitaceae Pathogen: Erwinia tracheiphila

Symptoms:

Drooping and wilting of infected leaves, which shrivel and dry up.

Infected stems become soft and pale then shrivel (ذبول), hard and dry.

b- Fire blight of Pear and Apple

Disease name: Fire blightPlant: Pear, ApplePathogen: Erwinia amylovora

Symptoms:Apple

Bark turns brownish black and soft → shrinks and hardens

Brown, black blotches along midrib and between veins then curl and shrivel.

Bacterial exudates (ooze) from apple fruit and stem.

Pear

Brown, blak blotches along midrib and between veins then curl and shrivel.

Immature fruit become water soaked, then shrivel, turn

black.

c- Black rot of crucifers

Disease name: Black rotPlant: CrucifersPathogen: Xanthomonas campestris

V-shaped chlorotic blotches at the margins of the leaves → chlorosis progress toward the midrib → affected area turn brown and dry.

Cabbage and cauliflower heads are discolored.

Symptoms:

3.Bacterial soft rots

Bacterial soft rots of vegetablesDisease name: Bacterial soft rots Plant: Vegetables ( potato, carrot,..), annual

ornamentals (iris), succulent stems, stalk or leaves (cabbage, lettuce,..).

Pathogen: Erwinia carotovora

Symptoms:

Affected area becomes soft and mushy, the surface becomes discolored and depressed.

Cracks develops the slimy mass exudates to the surface and turn brown.

Cruciferous plants and onions give off repulsive odor.

A whole fruit or tuber may be converted into a soft, watery, decay mass within 3-5 days.

4.Bacterial galls

Disease name: Crown gallPlant: Woody and herbaceous plants (> 60

families), mostly on pome and stone fruit trees, brambles and grapes.

Pathogen: Agrobacterium tumefaciens

Symptoms:Small, round, whitish soft

overgrowth on the stem

and roots (mainly near the

soil line) → the tumor

enlarge and become brown

(death and decay of

peripheral cells). Some

tumors are spongy while

others become woody and

hard.

5.Bacterial canker and gummosis

a- Bacterial canker and gummosis of stone fruit trees

Disease name: Bacterial canker and gummosis

Plant: Stone fruit trees (apricot, pear,olive,…)

Pathogen: Pseudomonas syringae

Bacterial canker:

Formation of cankers girdled the trunk or branches. Within few week, the branch or entire tree above the canker die.

Leaves show curling and turn yellow.

Symptoms:

Gummosis: gum exudation

b- Citrus canker

Disease name: Citrus cankerPlant: CitrusPathogen: Xanthomonas axonopodis

Symptoms:

Similar lesions are on young leaves, twigs and fruits.

Small round light green spots (lesions) → they rupture and appear corky with brown sunken centers and yellow halo.

Premature fruits drop.

6.Bacterial scabs

Common scab of potatoDisease name: Common scab Plant: Potato, root crops (beets,

radish,..)Pathogen: Streptomyces scabies

Symptoms:

Small brownish raised spots → enlarge, coalesce and become corky.

The lesions extend 3-4 mm deep in tuber

Plant diseases caused by parasitic higher plants

DodderrCuscuta spp.

WitchweedStriga spp.

1.DodderCuscuta spp.

Plant: alfalfa, onion, sugar beets, some ornamentals and potato.

Parasite: Cuscuta spp.(dodder)

Symptoms:

Orange or yellow strands around the

stem and the other aboveground parts

of the plant. The parasite enter their

haustoria directly to the phloem of the

host.

During late spring and in summer,

dodder produces clusters of white,

pink or yellowish flowers.

Infected host produce poor yield and

may be killed by parasite.

2.WitchweedStriga spp.

Plant: economic plants (corn, sugarcane, rice, cowpeas, tobacco, small grains,..)

Parasite: Striga spp.

Symptoms:

The parasitic roots are attached

to the host ones by its root

exudates → the root haustorium

penetrates the host roots → the

haustorium reach the vessels of

the host roots, from which it

absorb water and nutrients →

infected host became stunted

and chlorotic → wilt and die