Brown spots on tomato plants

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Brown spots on tomato plants

Post by RPM1 » Mon, 06 May 2002 05:30:00



They're watered enough.  Is it a lack of acid thing?

Ruth CM
Go here to see our horses and other stuff:
http://community.webshots.com/user/ironwood103

 
 
 

Brown spots on tomato plants

Post by Allegr » Mon, 06 May 2002 07:02:22


Hello Ruth,

Take a look at the info below. I don't know if it
is what you are talking about but it may help
you to identify the problem. Good luck,

Allegra
in zone 6-7 in Portland Oregon

"Bacterial spot, bacterial speck, and bacterial canker are widespread
diseases of tomato that can cause localized epidemics during warm (spot and
canker) or cool (speck), moist conditions. Bacterial spot can cause moderate
to severe defoliation, blossom blight, and lesions on developing fruit.
Bacterial speck also causes these symptoms but is usually not as severe in
Ohio as bacterial spot. Bacterial canker causes wilt, vascular
discoloration, scorching of leaf margins, and lesions on fruit.

 Symptoms
Foliar symptoms of bacterial spot and speck are identical (Figure 1). Small,
water-soaked, greasy spots about 1/8 inch in diameter appear on infected
leaflets. After a few days, these lesions are often surrounded by yellow
halos and the centers dry out and frequently tear. Lesions may coalesce to
form large, irregular dead spots. In mature plants, leaflet infection is
most concentrated on fully-expanded and older leaves and some defoliation
may occur. Spots may also appear on seedling stems and fruit pedicels. In
some cases, blossom blight may occur, causing flower ***. This is more
severe with bacterial spot and may result in a split fruit set which is
especially troublesome with determinate cultivars intended for mechanical
harvest.

Bacterial spot and speck can usually be differentiated by symptoms on
immature fruits. Bacterial spot lesions (Figure 1) are small water-soaked
spots that become slightly raised and enlarged until they are about 1/4 inch
in diameter. The centers of these spots later become irregular, light brown,
slightly sunken with a rough, scabby surface. In the early stages of
infection, a white halo may surround each lesion at which time it resembles
the fruit spot of bacterial canker. Small lesions which have not yet become
scabby are often confused with lesions of bacterial speck. Bacterial speck
appears on immature fruit as a black, slightly sunken stippling, eventually
causing lesions less than 1/16 inch in diameter (Figure 2). Fruit lesions
are not initiated on mature fruit in either disease.

Primary or systemic symptoms of bacterial canker (from infections
originating in seeds or young seedlings) include stunting, wilting, vascular
discoloration, development of open stem cankers, and fruit lesions. When
affected stems are split open lengthwise, a thin, reddish-brown
discoloration of the vascular tissue is observed, especially at the base of
the plant. On young seedlings in the greenhouse, lesions may appear as
raised pustules on leaves and stems. These plants rarely survive the season
in the field. Secondary symptoms in the field include leaf "firing"
(necrotic marginal leaf tissue adjacent to a thin band of chlorotic tissue;
Figure 3) and fruit lesions. Spots on fruit are relatively small (1/32 to
1/16 inch) surrounded by a white halo ("bird's-eye" spots; Figure 4). Canker
bacteria may also invade internal fruit tissues, causing a yellow to brown
breakdown.

Causal Organisms
Bacterial spot is caused by the bacterium, Xanthomonas campestris pv.
vesicatoria, which can be carried as a contaminant on the surface of
infested seed and has been found to overwinter in soil associated with plant
debris. Bacterial speck is caused by another bacterium, Pseudomonas syringae
pv. tomato. This bacterium may also be seedborne and can overwinter on plant
debris in soil and on the roots of many perennial plants. Bacterial canker
is caused by Clavibacter michiganensis subsp. michiganensis, which, unlike
the spot and speck pathogens, has the ability to infect tomato plants
systemically. It is seedborne and can survive on infested plant debris in
soil.

All three organisms may exist at low populations on leaf surfaces of
symptomless plants. At the onset of favorable conditions, these low
populations can increase rapidly and bacteria can then enter plants through
stomata or small wounds and begin infection. Bacteria can spread rapidly
with spattering rain and widespread epidemics may develop. Penetration of
tomato fruit occurs through wounds created by windblown sand, breaking of
hairs, or by insect punctures. Optimal conditions for bacterial spot and
canker are high moisture, high relative humidity and warm temperatures (75
to 90 degrees F). Bacterial speck is more likely to occur under cool (64 to
75 degrees F), moist conditions."

From University of Ohio


Quote:
> They're watered enough.  Is it a lack of acid thing?

> Ruth CM
> Go here to see our horses and other stuff:
> http://www.moonsgarden.com/

 
 
 

Brown spots on tomato plants

Post by Tom Jaszewsk » Mon, 06 May 2002 08:22:47




Quote:
>All three organisms may exist at low populations on leaf surfaces of
>symptomless plants. At the onset of favorable conditions, these low
>populations can increase rapidly and bacteria can then enter plants through
>stomata or small wounds and begin infection. Bacteria can spread rapidly
>with spattering rain and widespread epidemics may develop. Penetration of
>tomato fruit occurs through wounds created by windblown sand, breaking of
>hairs, or by insect punctures. Optimal conditions for bacterial spot and
>canker are high moisture, high relative humidity and warm temperatures (75
>to 90 degrees F). Bacterial speck is more likely to occur under cool (64 to
>75 degrees F), moist conditions."

If this is true then it is very likely a tea from vermicompost would
provide some resistence.

Regards,
Tom

Successful gardening is doing what has to be done when it has to be done
the way it ought to be done whether you want to do it or not.