Disease Management in
Organic Vegetables
Sally Miller
Department of Plant Pathology
Tri-State Organic IP Video
Program Session III
April 19, 2007
Organic Disease
Management

Importance of diseases varies among crops,
locations


“Diseases are the Achilles heel of organic tomato
production” Diver, Kuepper & Born 1995
Management requires an integrated
[systems] approach
Choose the Best Site

Well-drained fields


Good air movement


Water molds Pythium, Phytophthora
Promote rapid plant drying
Physical separation from other crops



Potatoes: late blight
Peppers: bacterial leaf spot
Conventionally produced crops
Improve Soil Quality


Reduce diseases by soilborne pathogens
Enhance composition of “beneficial”
organisms


Increase the abundance and diversity of the soil
microbial community
Increase soil organic matter

Cover crops/Green manures

Composts/Animal manures 
Effects of Compost on Plant
Health

Increases soil
suppressiveness to
diseases
High Tunnel Tomato
Treatment

Induces disease
resistance (“healthier
plants”)

Improves soil tilth

Improves soil moistureholding capacity
% Plants with
Sclerotinia
No
compost
26.9 a
Compost
5.8 b
P value
0.0033
Good Quality Compost

C:N ratio 30:1 at the beginning



90-120 days
Temperature 131-170F, 3 days in a static
aerated pile or 15 days in a windrow


Finished compost C:N ratio = ~10:1-14:1
Temperature> 15F above ambient indicates
unstable compost
Turn to assure entire pile reaches 131-170F
Maximizing Disease
Suppression

Compost




Cure 4 or more months
Incorporate into soil several months before
planting
Inoculate with beneficial microorganisms, e.g.
Trichoderma
Application


5-10 tons (dry weight)/A - rule of thumb
Apply every year until significant organic matter
improvement observed; watch for increases in P
Rotate Crops

Break the life cycles of pathogens

> 3 yrs between crops in the same family


Some pathogens cause disease among
multiple plant families
Include appropriate rotational crops to
increase soil organic matter
Exclude Pathogens

Destroy vines, etc. post-season




Removes sources of inoculum
Sterilize plant stakes between crops
Clean tools, equipment frequently
Prohibit tobacco use
Make Life Difficult for
Pathogens

Mulches

Plastic or plant-based



Row orientation



Reduce splash dispersal of pathogens
Protect fruit from soilborne pathogens
Maximize air movement
Minimize leaf wetness periods
Irrigation management
Variety Selection

Use resistant or tolerant varieties
wherever possible
Angular Leaf Spot - Cucumber

Favored by cool, wet
weather

Affects foliage and fruit

Seedborne

Some cultivars
advertised as resistant
Cultivar
Classy
Slice M ore
Talladega
2409
Thunder
Thunderbird
Stonewall
Sassy
Green Slam
Indy
Intimidator
Speedway
Foliar
AUDPC
R
R
T
R
R
R
R
408.4 dy
563.4 cd
571.6 dc
600.9 bcd
733.7 a-d
799.8 a-d
902.0 abc
907.0 abc
926.9 abc
985.4 ab
1074.1 a
1129.3 a
Fruit
incidence
(%)
0.2 d
1.0 bcd
6.7 a
2.9 a
7.2 a
3.7 ab
4.7 a
0.7 cd
0.3 cd
4.6 a
7.5 a
4.5 a
Mildews of Cucurbits

Downy mildew



Powdery mildew



New strains appeared in 2004
More aggressive on resistant varieties
Always appears in the
Midwest in mid-summer
Defoliates and predisposes
plants to other diseases
Disease resistance tables:
http://vegetablemdonline.ppath.cornell.edu/Tables/Ta
bleList.htm
Best performers - NCSU trials
2006 (slicing cucumbers)**
Variety
NC-Stratford- NCSU
Dasher II
Talladega
Thunder
Speedway
DM rating* Powdery
mildew
5-6
?
5-6
√
5-6
√
5-6
√
5-6
√
*Rating: 0=none; 1-2=trace; 3-4=slight; 5-6=moderate; 7-8=advanced; 9=dead plant
**http://cuke.hort.ncsu.edu/cucurbit/cuke/cukemain.html
Use “Clean” Seeds

Sanitizing seed treatment may be
needed: hot water treatment

Fact sheet: http://ohioline.osu.edu/hygfact/3000/pdf/3086.pdf
Water Bath Temperatures and
Treatment Times
Seed
F
Minutes
Brussels sprouts, eggplant, spinach,
cabbage, tomato
Broccoli, cauliflower, cucumber*, carrot,
collard, kale, kohlrabi, rutabaga, turnip
Mustard, cress, radish
122
25
122
20
122
15
Pepper
125
30
Lettuce, celery, celeriac
118
30
* Cucurbit seeds may be damaged by hot water treatment
Seed Treatment Cautions





Use new, high quality seed
Treat a small sample first and test for
germination
Treat close to time of planting (within
weeks)
Treat only once
Fact sheet: http://ohioline.osu.edu/hygfact/3000/pdf/3086.pdf
Producing Healthy Transplants

Practice good sanitation in the greenhouse





Use new or sanitized plug trays or flats and
pathogen-free mixes
Sanitize equipment
Install solid flooring; raise seedling trays
Limit movement of personnel and equipment
between greenhouses
Clean benches, greenhouse structure thoroughly
after the crop; close up greenhouse
Prevent Damping-off


Don’t overwater
Incorporate 10%
stable compost into
planting mix


Significantly reduces
damping-off
Drench or
incorporate
biocontrol products
Prevention of Pythium
damping-off
Treatment
Untr eated control w/o Pythium
Composted cow manure
Omega Grow
Trichoderm a hamatum 382
Prestop
Phosphonate
Serenade ASO 1.0%
Serenade ASO 2.0%
Untr eated control + Pythium
Omega Grow Plus
Serenade ASO 0.5%
Seacide
Mycostop
% damping -off
PrePostemergence emergence
6.3 j
0.0 d
39.6 h
0.5 cd
47.9 g
0.5 cd
56.8 ef
1.1 bcd
64.1 de
3.2 abc
66.7 cd
2.1 a-d
66.7 cd
4.2 a
69.8 bcd
1.6 a-d
70.3 bcd
0.5 cd
72.9 abc
0.5 cd
74.5 abc
3.7 ab
75.5 ab
0.5 cd
77.1 ab
2.6 a-d
Prevention of Rhizoctonia
damping-off
Treatment
Untr eated control w/o R. solani
Composted cow manure
Trichoderm a hamatum 382
Omega Grow Plus
Serenade ASO 0.5%
Untr eated control w/ R. solani
Serenade ASO 1.0%
Serenade ASO 2.0&
% Damping -off
PrePostemergence emergence
1.6 k
0.0 b
4.7 jk
0.0 b
9.4 ijk
1.1 ab
16.7 hi
1.1 ab
30.2 def
1.6 ab
33.3 cde
2.6 ab
56.8 b
2.1 ab
74.0 a
0.5 ab
Preventing Other Diseases

Do not raise exotic or experimental vegetable
varieties, or plants from saved seed, in the
same greenhouse with commercial seedlings
unless all seeds are treated

Avoid raising or holding ornamental plants
and vegetables in the same greenhouse

Exclude insects (may carry viruses)

Maintain conditions in the greenhouse that do
not favor disease development

Maintain relative humidity as low as possible



Good air circulation
Proper temperatures
Handle plants as little as possible
Field Options: Pre-plant

Biofumigation




Mustards, broccoli residue
Muscodor
Broad-spectrum activity
Biocontrols

Contans

Narrow-spectrum (Sclerotinia only)
Post-Planting Options

Bringing out the
Band-Aids

Biological products
Chemical products
Plant extracts/oils
Compost teas



Disease Management Alternatives for Organic Tomatoes
Treatment
Control - water to run off
Humega
Timor
StorOx
Biodynamic 508- Equisetum arvense
Kaligreen
Sonata + Champion WP
Serenade
Timorex
Trilogy
Garlic Barrier
SW-3
Sonata
StorOx alternated with Champion WP
Serenade + Champion WP
Champion WP
Bordeaux mixture
% Foliar
disease
66.0
75.9
67.6
61.4
59.0
47.9
45.6
44.3
44.1
39.5
39.4
37.1
37.0
25.0
21.4
10.8
5.0
ab
a
ab
ab
ab
abc
abc
abc
abc
bcd
bcd
bcd
bcd
cde
cde
de
e
Disease Management:Squash

Winter squash ‘Taybelle’

Floating row covers +
pyrethrum to protect plants
from beetles

Foliar sprays







Armicarb
Milk
Stylet oil
Neem oil
Serenade
Compost tea
Sulfur
Powdery Mildew Management
Treatment and rate
Serenade Max 1 lb/A + Kocide 2 lb/A
Serenade Max 2 lb/A + Kocide 2 lb/A
Sulfur 16 lb/A
Whole milk 50%
Mineral oil (stylet-oil) 3.5 qts/100 gals
Armicarb- 100 5.0 lb/A+ Biolink 1.5 qt/100 gal
Armicarb-100 2.5 lb/A + Biolink 1.5 qt/100 gal
Soil soup compost tea 100%
Neem oil 0.75 %
Soil soup compost tea 33%
Untreated control, protected
Untreated control, non-protected
%
Powdery
mildew
2.9 g
2.2 g
5.0 g
5.9 g
11.8 ef
11.6 f
14.7 ef
17.0 e
23.1 d
31.8 c
52.9 b
80.7 a
Bacterial Wilt
Treatment and rate
Armicarb- 100 5.0 lb/A+ Biolink 1.5 qts/100 gal
Armicarb-100 2.5 lb/A + Biolink 1.5 qts/100 gal
Whole milk 50%
Mineral oil (Stylet-oil) 3.5 qts/100 gals
Neem oil 0.75 %
Serenade Max 1 lb/A + Kocide 2 lb/A
Serenade Max 2 lb/A + Kocide 2 lb/A
Soil soup compost tea 33%
Soil soup compost tea 100%
Sulfur 16 lb/A
Untreated control, protected
Untreated control, non-protected
Bacterial wilt
% wilted
**
0.0 b
3.3 b
0.0 b
1.7 b
0.0 b
0.0 b
0.0 b
0.0 b
0.0 b
0.0 b
0.0 b
13.3 a
National Organic
Standards/Related Subjects

The National Organic Program


USDA links to organic-related material


http://www.ams.usda.gov/nop/
http://www.ams.usda.gov/nop/nop2000/nop2/fedor
ganlinks.htm
Organic Materials Review Institute

http://www.omri.org/
Additional Information…..

ATTRA (Appropriate Technology Transfer for
Rural Areas)


Organic Agriculture Consortium


http://www.attra.org
http://www.organicaginfo.org
NEON (Northeast Organic Network)

http://www.neon.cornell.edu/



Anusuya Rangarajan
Department of Horticulture121 Plant Science Building
Cornell University, Ithaca, NY 14853
Phone:(607) 255-1780




ATTRA Sustainable Management of Soilborne Diseases http://attra.ncat.org/attrapub/soilborne.html
Compost Production and Use (MSU)
http://www.hrt.msu.edu/course/HRT491/Com
post/CombinedCompost.pdf
Composting at Home (OSU)
http://ohioline.osu.edu/com-fact/0001.html
http://www.oardc.ohio-state.edu/millerlab