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Brown Spot (Alternaria alternata)

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deluxestogie

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Brown Spot

Garden20170712_2827_BrownSpot_600.jpg

A lug of Virginia Bright Leaf with Brown Spot.

Brown Spot is a fungal disease that causes brown spots, composed of characteristic concentric rings. Alternaria alternata, the causative fungus, is also responsible for "Early Blight" in tomatoes, typically causing lower branches on the tomato vine to turn brown and die.

Garden20170712_2828_BrownSpot_det_600.jpg

The individual lesions can range in size from a tiny dot to several inches across.

On tobacco leaf, each area of the lamina affected by the fungal infection develops a hard, circular blemish, surrounded by early yellowing and eventual necrosis. It typically affects lower leaves, then slowly spreads to upper leaves. In damp shed conditions, the lesion may continue to grow, but is not likely to infect other leaves there. In the field, however, ideal conditions for growth of Brown Spot are a temperature of 85ºF and high humidity. A long stretch of rainy days in mid-to-late season, together with high temperatures are the highest risk times. During dry conditions, the fungus is able to spread from earlier lesions to other plants. Closer plant spacing also encourages spread.

The fungus dwells in the soil, so crop rotation is helpful (but must be to a crop unrelated to tobacco). Earlier priming or earlier stalk harvesting limits continued spread on that plant.

Univ. Georgia Ag. Extension Service said:
Brown spot, caused by Alternaria alternata, is a foliar disease that usually develops from mid season to
harvest. It begins in the lower leaves and works up the plant. Brown spot is favored by wet weather, excess
nitrogen and tight plant spacing. Fungicides are not effective for brown spot control.

http://caes2.caes.uga.edu/commoditi.../documents2013/8TobaccoDiseaseControl2013.pdf

A limited Brown Spot infection simply results in some dead spots on some of the leaf. The spots often fall out during kilning or flue-curing, and the leaf can be smoked safely.

I found that the cigar variety Jalapa is very susceptible to Brown Spot, causing fairly large lesions that affected most of the leaves of entire plants. For this reason, and since I frequently see early blight in my tomatoes--suggesting that the organism is common in my soil, I no longer grow Jalapa.

Bob
 

Hasse SWE

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That good information about a bad thing Bob.- my Tomatoes only have those problem some seasons (think it happens one or two season out of five). So if you have some seed laying I can grow them.
 

wooda2008

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Good to know. Now I have another reason to be OCD about my tomato plants; They're right next to the tobacco.

I've been pruning leaves as soon as they show any sign of early blight and mulching heavily with fresh grass clippings and leaves to keep soil splash to a minimum.
 

BigBonner

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Years back before I started growing cigar varieties I would put two rows of tomatoes in the middle of one of my Burley tobacco fields . These produced the best tomatoes and plenty of them . But even if the burley had of took on TMV or any other virus , I did not worry as burley was stripped and sold and those viruses or blue mold spots did not effect Big tobacco buying any burley crop so long as the color was right .

I have been very worried about the storm Cindy bringing up blue mold from the Gulf . . I have not seen any yet , just tobacco worms .
 

Hasse SWE

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I like to read about different tobacco variants and most ask a question is it really possible that a variant have:"highly resistant to the Blackish Paw, moderately resistant to the environmental necrosis.Suspected to: Brown spot".Ain't Blackish paw and Brown spot the same thing??
 

deluxestogie

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I've never heard of "Blackish paw" as a tobacco disease. If it is caused by Alternaria alternata, then it's the same as Brown Spot. Or, it may be a computer translator invention.

Bob
 

Hasse SWE

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Bob that is what I was thinking. But to see that a variant (same variant) have high resistance against it and same time is suspected for it was making me wondering about it.. I didn't see it before I was reading my own text..
 
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