Title: SEED-BORNE DISEASE AND YOU
1SEED-BORNE DISEASE AND YOU
Jodi Lew-Smith High Mowing Seeds
2As a seed grower, what do I need to worry about?
- RED ALERT diseases
- highly virulent, highly seed-borne
- ORANGE ALERT diseases
- moderately virulent, highly seed-borne
- OR highly virulent, moderately seed-borne
- YELLOW ALERT diseases
- Moderate or weakly virulent, moderate or weakly
seed-borne
3BRASSICA TOP SEED-BORNE DISEASES
- BLACK ROT bacteria (Xanthomonas campestris)
- RED ALERT
- Highly virulent, highly seed-borne
- Distinction of being 1 among top ten seed-borne
diseases - Spreads quickly in warm, humid weather
- New strip test available from Agdia
- BLACKLEG fungus (Phoma lingam / Leptosphaeria
maculans ) - RED ALERT
- Highly virulent, highly seed-borne
- Spreads quickly in warm, humid weather
4MORE BRASSICA SEED-BORNE DISEASES
- ALTERNARIA DISEASES
- Orange Alert
- Three different species, all similar for purposes
of control - Less virulent than former two, but can be
seed-borne and should be controlled
5BLACK ROT SYMPTOMS
Spreads rapidly in warm, humid weather
6BLACK ROT SYMPTOMS
Leaf margins, primarily veins
7BLACKLEG SYMPTOMS
Stem cankers encircle stems, typically at base,
black pycnidia visible within cankers
8BLACKLEG SYMPTOMS
Dark grey lesions on roots, eventual spots on
leaves
9ALTERNARIA SYMPTOMS
Classic bullseye spot on leaves
10ALTERNARIA SYMPTOMS
11BRASSICA SEED-BORNE DISEASE CONTROL
- Obtain disease-free seed, do not take any
chances, heat-treat seed for additional security - Make sure all crop debris is completely
incorporated and/or removed - Avoid dense plantings, avoid working in wet
fields - Practice 4-year rotation with eradication of all
crucifer weeds before planting brassica seed
crops again - Preventive copper sprays
12LETTUCE TOP SEED-BORNE DISEASE
- LETTUCE MOSAIC VIRUS (LMV)
- RED Alert
- Highly virulent, highly seed-borne
- Very common, especially on the west coast
- Spreads by insects, mainly leaf hoppers
13LETTUCE MOSAIC VIRUS SYMPTOMS
Difficult to distinguish from CMV in fields, but
tests are readily available
14LETTUCE MOSAIC VIRUS SYMPTOMS
15LETTUCE MOSAIC CONTROL
- Primary control is disease-free seed
- Seed testing is widely available
- Once confirmed in MTO seed field, plants are
destroyed - Tolerance for low levels in non-MTO crops
16CARROT TOP SEED-BORNE DISEASES (LEAF BLIGHTS)
- BACTERIAL BLIGHT bacteria (Xanthomonas campestris
pv. carotae) - Orange Alert
- Moderately virulent, highly seed-borne
- Primarily causes yield losses due to poor seed
germination - ALTERNARIA BLIGHT fungus (Alternaria dauci, also
A. radicina) and CERCOSPORA BLIGHT fungus
(Cercospora carotae) - Orange Alert
- - Moderately virulent, moderately seed-borne
- - Can occur in the same field, cause yield loss
due to leaf loss
17Bacterial Blight symptoms
Lesions turn dark brown and shiny, and progress
down petiole
18Cercospora Blight symptoms
Spots more round, better defined
19Alternaria Blight symptoms
Lesions more irregular, typically on margins
20CARROT LEAF BLIGHT CONTROL
- Obtain disease-free seed, heat treat where
possible for added security - Avoid overhead irrigation
- Avoid working in wet fields
- Allow 2-year rotation for debris to break down in
field - Avoid highly-susceptible varieties which increase
inoculum levels - Preventive copper sprays
21ONION TOP SEED-BORNE DISEASES
- BOTRYTIS NECK ROT fungus (Botrytis allii, also B.
aclada and B. byssoidea) (Disease also called
SCAPE AND UMBEL BLIGHT) - Orange Alert
- Highly virulent, degree of seed transmission
disputed - Causes neck rot to bulbs and attacks stems and
umbels of seed stalks - WHITE ROT fungus (Sclerotium cepivorum,
Sclerotinia sclerotiorum) - Orange Alert
- Doesnt actually travel on seed, but black
sclerotia can easily get mixed with seed because
they look so similar - Most prevalent in cool seasons and poorly-drained
fields - Sclerotia can persist in soil for up to fifteen
years
22White Rot Symptoms
23White Rot Symptoms
Fluffy white mold, black spores and sclerotia
24Onion Disease Control
- Watch out for sclerotia in incoming seed
- Avoid overhead irrigation
- Avoid working in wet fields
- Scout for mold throughout season
- Do not allow any infected bulbs to go to seed.
Once sclerotia are mixed with seed, theyre
nearly impossible to separate completely
25TOMATO TOP SEED-BORNE DISEASES
- TOMATO MOSAIC VIRUS (TMV)(Effectively same as
Tobacco Mosaic Virus) - - Red Alert- Highly virulent, highly
seed-borne- Commercial damage may range from
light to heavy, but disease extremely hard to
eradicate from seed - - Good strip test available from Agdia
- BACTERIAL DISEASES (Bacterial canker
(Corynebacterium michiganense pv. michiganense),
Bacterial Spot (Xanthomonas campesiris pv,
vesicatoria), Bacterial Speck (Pseudomonas
syringae pv. tomato)- Orange Alert- Highly to
moderately virulent, highly seed-borne- Cause
considerable damage, but eradicated from seed by
fermentation and/or hot water treatment
26Tomato Mosaic Virus symptoms
27Bacterial Canker Symptoms
Round, pale, birdseye spots
28Bacterial Spot Symptoms
Scabby, raised spots. Infects green fruit.
29Bacterial Speck Symptoms
Spots smaller, more shallow
30Tomato Disease Control
- For TMV, use strip tests to assay seed
- If TMV appears, destroy plants
- For bacterial diseases, heat-treat seed ahead of
time - Ferment all seed during harvest
31What is a growers responsibility with respect to
seed-borne disease?
- Knowledge of which diseases are seed-borne
- Careful scouting of crops to spot symptoms
- Confirmation of diagnosis with Extension or other
diagnostic service if symptoms appear - Consultation with seed company to determine
course of action
32What are the scenarios when I find ANY kind of
disease in a seed crop?
33(No Transcript)
34I. If its not a seed-borne disease, treatment
would be applied to keep the plants alive to make
seed
E.g. common leaf-spot diseases such as early
blight
35II. If its a disease of low to moderate
virulence, and the seed could be treated, it may
be harvested and flagged for hot water treatment
E.g. possible for some bacterial spot diseases in
tomato or pepper
36III. For most seed-borne diseases, the crop is
typically destroyed if the disease is present
This avoids spending any more time or money on a
crop that wont make saleable seed
37SEED TREATMENTS FOR DISEASE ERADICATION
- Hot Water
- Bleach
- Experimental treatments
38HOT WATER TREATMENT
- Advantages
- Most effective
- Kills disease on both inside and outside of seed
- Can fully eradicate heat-sensitive pathogens
- no residue
- Disadvantages
- requires an investment
- Requires careful handling, can damage seed
- Cant be done as easily during harvest, so often
requires wetting and re-drying seed
39Hot Water Requirements
- 42-50C (118-122F)
- 15-25 minutes
- Seed fully immersed, typically in cotton bags
- NEED a setup with temperature control
- Budget option is deep fryer (50-150)
- Better option is lab-grade water bath incubator
(150-800 on ebay)
40Shaking Water bath
41Bleach Treatment
- Advantages
- Fast, easy, requires little to no special
equipment - Can be done during washing of wet-seeded crops
- Good for reduction but not eradication of disease
- Only organic option for large-seeded crops that
cant be hot water treated - Disadvantages
- Not likely to completely eradicate disease
- Requires careful handling, can damage seed coat
- Kills disease only on seed coat, not internally
42Bleach Requirements
- Soak seed in a 5-10 bleach solution
- usually 5-10 minutes
- Can be done by adding bleach to final wash on wet
seed harvest
43Other Treatments
- Natural II
- Biocontrol agents, e.g.
44Print Resources
- 1. Common Laboratory Seed Health Testing Methods
for Detecting Fungi. 2003. S.B. Mathur, O.
Kongsdal. The International Seed Testing
Association. Bassersdorf, CH-Switzerland. - 2. Crucifer Diseases A Practical Guides for
Seedsmen, Growers, and Agricultural
Advisors.1994. J. Cucuzza, J. Dodson, B. Gabor,
J. Jiang, J. Kao, D. Randleas, V. Stravato, and
J. Watterson. Plant Pathology Department,
Petoseed Company, Inc. Saticoy, California. - 3. The Diagnosis of Plant Diseases A Field and
Laboratory Manual Emphasizing the Most Practical
Methods for Rapid Identification. 1972. R.B.
Streets, Sr. The University of Arizona Press,
Tucson, Arizona. - 4. Diseases and Pests of Vegetable Crops in
Canada An Illustrated Compendium. 1994. R.J.
Howard, J.A. Garland, W.L. Seaman, Eds. The
Canadian Phytopathological Society and the
Entomological Society of Canada. M.O.M. Printing
Ltd. Ottawa, Ontario, Canada. - 5. Hortus Third, A Concise Dictionary of Plants
Cultivated in the United States and Canada. 1976.
L. H. Bailey. Macmillan Publishing. New York, New
York. - 6. Identifying Diseases of Vegetables. 1994. A.A.
MacNab, A.F. Sherf, J.K. Springer. Penn State
College of Agricultural Sciences. University
Park, Pennsylvania. - 7. Illustrated Genera of Imperfect Fungi, 4th
Edition. 1998. H.L. Barnett, B.B. Hunter, The
American Phytopathological Society. APS Press.
St. Paul, Minnesota. - 8. Laboratory Guide for Identification of Plant
Pathogenic Bacteria, 3rd Edition. N.W. Schaad,
J.B. Jones, W. Chun, Eds. The American
Phytopathological Society. APS Press. St. Paul,
Minnosota. - 9. Plant Pathology, 3rd Edition. 1988. G.N.
Agrios. Academic Press, Inc. San Diego,
California. - 8. Principles of Seed Pathology, 2nd Edition.
1996. V.K. Agarwal, J.B. Sinclair. CRC Press,
Inc., Lewis Publishers. Boca Raton, Florida. - 10. Rules for Testing Seeds. 1999. Association of
Official Seed Analysts. Lincoln, Nebraska. - 11. Seed to Seed Seed Saving and Growing
Techniques for Vegetable Gardeners, 2nd Edition.
2002. S. Ashworth. Seed Savers Exchange, Inc.
Decorah, Iowa. - 12. Tomato Diseases A Practical Guides for
Seedsmen, Growers, and Agricultural
Advisors.1997. B. Gabor and W. Wiebe, Eds. Plant
Pathology Department, Seminis Vegetable Seeds,
Inc. Saticoy, California. - 13. World Economic Plants A Standard Reference.
1999. J. H. Wiersema and B. Leon. Agricultural
Research Service, United States Department of
Agriculture. CRC Press, Inc. Boca Raton, Florida.
45Online Resources
- Common Names of Plant Diseases
- http//www.apsnet.org/online/common/toc.asp
- Cornell Universitys Plant Disease Diagnostic
Clinic Homepage http//plantclinic.cornell.edu/
Default.htm - Simplified Fungi Identification Key
- http//www.plant.uga.edu/Extension/pubs/fungikey.p
df - SBML Fungal Databases Selecting Fungus-Host
Distributions - http//nt.ars-grin.gov/fungaldatabases/fungushost/
fungushostframe.cfm - Vegetable Diseases Fact Sheets listed by Crop
- http//vegetablemdonline.ppath.cornell.edu/cropind
ex.htm - Plant diseases directory for agricultural crops
Manitoba agriculture, food, and rural initiatives - http//www.gov.mb.ca/agriculture/crops/diseases/in
dex.html - Plant Disease Information System
- http//www.pdis.org/
- Seedborne diseases and their control Principles
and practice. R.B. Maude. 1996. CAB
International, Tucson, AZ. - Hot water treatment of vegetable seeds to
eradicate bacterial plant pathogens in organic
production systems Online. S. Miller and M.
Lewis Ivey. 2005. Ohio State Extension Bulletin
HYG-3086-05. Available at http//ohioline.osu.edu
/hyg-fact/3000/pdf/3086.pdf (verified 10 March
2010).
46Seed Art