Group Title: Press bulletin
Title: Lettuce rot
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 Material Information
Title: Lettuce rot
Series Title: Press bulletin
Physical Description: 2 leaves : ; 23 cm.
Language: English
Creator: Burger, O. F ( Owen Francis ), 1885-1928
University of Florida -- Agricultural Experiment Station
Publisher: Florida Agricultural Experiment Station
Place of Publication: Gainesville
Publication Date: 1912
Subject: Lettuce -- Diseases and pests -- Florida   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
non-fiction   ( marcgt )
Statement of Responsibility: by O.F. Burger.
General Note: Caption title.
General Note: "October 19, 1912."
 Record Information
Bibliographic ID: UF00090323
Volume ID: VID00001
Source Institution: University of Florida
Holding Location: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: oclc - 83553959

Full Text




By O. F. Burger
Lettuce Rot caused much loss to the lettuce growers last season. Un-
less special precautions are taken this year, it is likely to cause damage
again. Lettuce Rot is distinguished from Lettuce Drop and Root-Knot, by
there being no wilting or yellowing of the leaves. The disease first shows
in the seed-bed as small black spots on the leaves. These spots increase in
size until the whole leaf is blackened and drops off. In the field, the leaves
become black spotted, and sometimes the edges turn brown, and then blacken
as if injured by frost.. Most damage is done to the headed lettuce. The
center of the head begins to blacken, and then becomes soft. The disease
spreads outward until the whole head is a black decaying mass.
In some districtsthere were few fields which were not infected last year.
The loss to different growers varied from one-third to the whole of the crop.
Much of the infection takes place in the seed-bed, therefore it is neces-
sary to watch closely and prevent any infected plants being transplanted
to the field. If a seed-bed becomes infected discard it; pull up the plants,
carry them off the field, and bury or burn them. Remove all infected plants
from the fields, as each diseased plant will infect others. Do not throw
infected plants in the alley ways.
The field must be well drained, as excess of moisture is a very important
factor in the spread of the disease.
Seed Beds
Young plants succumb readily to the attack of Lettuce Rot. They soon
show the signs of being diseased, which have already been described. At
times the seed-beds become so badly infected that large areas become black
and putrid. There are many insects which feed on the decaying plants.
It is probable that these insects, flying to healthy plants, are able to infect

October 19, 1912

them by carrying the bacteria on their bodies. Seed-beds showing the least
signs of infection should be destroyed.
Lettuce Rot Is caused by bacteria organism known as Pseudomnas
sp. Infected lettuce plants were taken from the fields, and cultures of the
bacteria obtained in our laboratory. Some of the cultures were then brushed
on healthy lettuce plants, which were kept growing in the-Experiment Sta-
tion greenhouse. Each plant, after it had been inoculated, was wrapped in
oiled paper to retain moisture. In two or three days the disease made its
appearance. In ten days after inoculation the plants were black and pulpy.
Other plants, wrapped in paper, but not inoculated, were healthy at the
end of ten days. When a plant that had already headed was inoculated, no
wrapping was necessary to produce the disease. The moisture contained in
the head was sufficient for the growth of the bacteria.
Many times on account of dry weather the grower believes that he
has got rid of the disease. But during a dry spell it remains inactive. When
the plants begin to head, and moisture enough is conserved, the disease shows
in the head. At shipping time the grower may find fifty per cent, of such
lettuce rotting in the center of the head.

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