Spread of the disease

Title: Angular leaf spot: a bacterial disease in strawberries in Florida
Full Citation
Permanent Link: http://ufdc.ufl.edu/UF00066816/00001
 Material Information
Title: Angular leaf spot: a bacterial disease in strawberries in Florida
Physical Description: Book
Creator: Peres, Natalia A.
Publisher: Plant Pathology Department, Cooperative Extension Services, Institute of Food and Agricultural Sciences, University of Florida
Funding: Florida Historical Agriculture and Rural Life
 Record Information
Bibliographic ID: UF00066816
Volume ID: VID00001
Source Institution: Marston Science Library, George A. Smathers Libraries, University of Florida
Holding Location: Florida Agricultural Experiment Station, Florida Cooperative Extension Service, Florida Department of Agriculture and Consumer Services, and the Engineering and Industrial Experiment Station; Institute for Food and Agricultural Services (IFAS), University of Florida
Rights Management: All rights reserved by the source institution and holding location.

Table of Contents
        Page 1
        Page 2
    Spread of the disease
        Page 3
        Page 4
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Angular Leaf Spot: A Bacterial Disease in Strawberries in Florida

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Angular Leaf Spot: A Bacterial Disease in

Strawberries in Florida1

Natalia A. Peres, Silvia I. Rondon, James F. Price, and Daniel J. Cantliffe2

Angular Leaf Spot (ALS) is a bacterial disease caused by Xanthomonasfragariae Kennedy & King,
a pathogen highly specific to wild and cultivated strawberry, Fragaria x ananassa Duchesne (Legard
et al. 2003). ALS is an important disease on winter strawberry production worldwide. In the U.S., it
ranks 6th in economic importance after gray mold (B. ,i, 1,, cinerea L.), verticillium wilt (Verticillium
alboatrum Reinke & Berth), powdery mildew (Sphaerotheca macularis L.), anthracnose
(Colletotrichum spp.), and pythium root rot (Pythium spp.) (Sorensen et al. 1997). The rapid spread
of ALS is influenced by the increasing rate of interchange of plant material.

ALS was first reported in Minnesota in 1960 and since then it has been found in almost all cultivated
strawberry areas in the U.S. (Funt et al. 1997). In California, the largest U.S. producer of fresh
strawberries, ALS is a minor disease that occurs especially during rainy weather or when overhead
sprinkler irrigation is used (Strand 1993). ALS is the only strawberry disease in Florida caused by a
bacterium (Howard et al. 1985). Little is known regarding the epidemiology of ALS (Funt et al.
1997; Mass 1998); however, development of the disease is favored by warm days (200C/680F) and
cold nights (2-40C/ 36-390F) (Howard et al. 1985).


X fragariae, the causal agent of ALS, is a slow-growing, Gram-negative bacterium that produces
water-soaked lesions on the lower leaf surfaces ( Figure 1 ). Lesions begin as small and irregular
spots on the undersurface of the leaflets. When moisture is high on the leaves, lesions ooze sticky
droplets of bacteria (Howard et al. 1985). As the disease develops, these lesions enlarge and coalese
to form reddish-brown spots, which later become necrotic (Figure 2 ). A practical way to recognize
the disease is to place the leaves against a source of background light where the translucent spots can
be seen ( Figure 3 ).

During severe epidemics, the pathogen also can cause lesions on the calyx of fruit that are identical
to foliar lesions (Figure 4 ) and when severe, can make the fruit unmarketable (Legard et al. 2003).
The tissue with older damage eventually dies and dries up, giving leaves a ragged appearance (Strand

Angular Leaf Spot: A Bacterial Disease in Strawberries in Florida


CREDITS: Univ. of Florida, GCREC

Figure 1. Water soaked lesions of Angular Leaf Spot.

CREDITS: Univ. of Florida, GCREC

Figure 2. Reddish-brown spots of Angular Leaf Spot.

CREDITS: Univ. of Florida, GCREC

Figure 3. Translucent spots of Angular Leaf Spot.

~ "" --

Angular Leaf Spot: A Bacterial Disease in Strawberries in Florida

CREDITS: Univ. of Florida, GCREC

Figure 4. Water soaked lesion of Angular Leaf Spot on the calyx.

Spread of the Disease

The primary source of inoculum in a new field is contaminated transplants (Mass 1998). Secondary
inoculum comes from bacteria that exude from lesions under high moisture conditions. Bacteria can
survive on dry infested leaves and tissue buried in the soil for up to 1 year (Roberts et al. 1997;
Strand 1993). The pathogen can be spread easily by harvesting operations when wet and cool
conditions favor the production of bacterial exudate. The pathogen also can be dispersed by rain and
overhead sprinkler irrigation. If the disease invades the vascular system of the plant, the disease will
be difficult to control. Affected plants may wilt and die.

Control Methods

The best way to control ALS is to use pathogen-free transplants. Hydrogen dioxide and copper-based
products can provide effective control of the disease in some instances, but low rates of copper
should be used since phytotoxicity has been documented with repeated sprays. Growers should avoid
harvesting and moving equipment through infected fields when the plants are wet. Minimizing the
use of overhead sprinklers during plant establishment and for freeze protection will also reduce the
spread of the disease.

Literature Cited

Funt, R.C., M.A. Ellis, and C. Welty. 1997. Midwest small fruit pest management handbook. Ohio
State University. 196 pp.

Howard, C.M., A.J. Overman, J.F. Price, and E.E. Albregts. 1985. Diseases, nematodes, mites, and
insects affecting strawberries in Florida. University of Florida, Agricultural Experimental Station,
Institute of Food and Agricultural Sciences. 51 pp.

Legard, D.E., M. Ellis, C.K. Chandler, and J.F. Price. 2003. Integrated management of strawberry
diseases in winter fruit production areas, Pp 111-124. In The Strawberry: a book for growers. N.
Childers (ed.). Institute of Food and Agricultural Sciences, Horticultural Sciences Department,
University of Florida, Gainesville. Norm Childers Publications. 246 pp.

Mass, J.L. 1998. Compendium of strawberry diseases. 2nd edition. APS press, St Paul, MN.

Roberts, P.D., R.S. Berger, J.B. Jones, C.K. Chandler, and R.E. Stall. 1997. Disease progress, yield

Angular Leaf Spot: A Bacterial Disease in Strawberries in Florida

loss, and control ofXanthonomafragariae on strawberry plants. Plant Dis. 81: 917-921.

Strand, L.L. 1993. Integrated pest management for strawberries. University of California, State Wide
Integrated Pest Management Project. Division of Agriculture and Natural Resources. Publication
3351. 142 pp.

Sorensen, K. A., W.D. Gluber, N.C. Welch and C. Osteen. 1997. The importance of pesticides and
other pest management practices in U.S. strawberry production. North Carolina Cooperative
Extension Service. NAPIAP 1-CA-97. 242 pp.


1. This is document PP-199, a publication of the Plant Pathology Department, Florida
Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of
Florida. Publication date: June 2004. Please visit the EDIS Website at http://edis.ifas.ufl.edu.

2. Natalia A. Peres, assistant professor, Gulf Coast Research Center and Education Center;
Silvia I. Rondon, post doctorate, Horticultural Sciences Department; James F. Price,
associate professor, Gulf Coast Research and Education Center; Daniel J. Cantliffe,
professor, Horticultural Sciences Department.

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U.S. Department of Agriculture, Cooperative Extension Service, University of Florida, IFAS, Florida
A. & M. University Cooperative Extension Program, and Boards of County Commissioners
Cooperating. Larry Arrington, Dean.

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