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1.Bacterial spots and blights. a- Wildfire of tobacco Disease 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.

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1.Bacterial spots and blights

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1 bacterial spots and blights
1.Bacterial spots and blights

a- Wildfire of tobacco

Disease name:Wildfire

Plant:Tobacco (Nicotiana tabacumL.)

Pathogen:Pseudomonas syringae


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
b- Bacterial spot of tomato and pepper

Disease name: Bacterial spot

Plant: Tomato, Pepper

Pathogen: Xanthomonas campestris




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

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



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
c- Bacterial speck of tomato

Disease name: Bacterial Speck

Plant: Tomato

Pathogen: Pseudomonas syringae


Lesions are similar to bacterial spot but smaller

2 bacterial vascular wilts
2.Bacterial vascular wilts

a- Bacterial wilt of cucurbits

Disease name:Bacterial wilt


Pathogen:Erwinia tracheiphila


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
b- Fire blight of Pear and Apple

Disease name: Fire blight

Plant: Pear, Apple

Pathogen: Erwinia amylovora




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

Bacterial exudates (ooze) from apple fruit and stem.

Bark turns brownish black and soft → shrinks and hardens



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
c- Black rot of crucifers

Disease name: Black rot

Plant: Crucifers

Pathogen: 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.

3 bacterial soft rots
3.Bacterial soft rots

Bacterial soft rots of vegetables

Disease name:Bacterial soft rots

Plant:Vegetables ( potato, carrot,..), annual ornamentals (iris), succulent stems, stalk or leaves (cabbage, lettuce,..).

Pathogen:Erwinia carotovora


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.

4 bacterial galls
4.Bacterial galls

Disease name:Crown gall

Plant:Woody and herbaceous plants (> 60 families), mostly on pome and stone fruit trees, brambles and grapes.

Pathogen:Agrobacterium tumefaciens


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
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.



gum exudation

b citrus canker
b- Citrus canker

Disease name: Citrus canker

Plant: Citrus

Pathogen: Xanthomonas axonopodis


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
6.Bacterial scabs

Common scab of potato

Disease name:Common scab

Plant:Potato, root crops (beets, radish,..)

Pathogen:Streptomyces scabies


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

The lesions extend 3-4 mm deep in tuber

1 dodder cuscuta spp
1.DodderCuscuta spp.

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

Parasite: Cuscuta spp.(dodder)



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 witchweed striga spp
2.WitchweedStriga spp.

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

Parasite: Striga spp.



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