learn about what diseases are important for your crop/location fileballad + biotune a, x product...
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Diagnosis and Prevention of VegetableDiseases in Organic systems
Daniel S. EgelDepartment of Botany and Plant Pathology
Purdue University
4369 N. Purdue Rd.
Vincennes, IN 47591
(812) 886-0198 [email protected]
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Learn about what diseasesare important for your
crop/location
VerticilliumTMVTimber rot
SpeckSeptoriaRoot knot
Leaf moldLate blightGray mold
Fusarium wiltFusarium crown rotEarly blight
CankerBacterial spotAnthracnose
Tomato Diseases
There may be many possible diseases listed for your crop.
However, not all of them will be important for your location
and situation. It makes sense to learn which diseases are
most important for your area and to learn the
characteristics of each disease.
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Unusual in IndianaYesNoLate blight
CommentsResistance
Maybe
Seed
borneDisease
Primarily greenhouse
diseasesNoNo
Leaf mold/
gray mold
NoNoEarly blight/
Septoria
NoYesCanker
SpeckYesBacterialspot/speck
Stake & mulchNoYesAnthracnose
Residue borne tomato diseases-rotations of
2-4 years and fall tillage critical
Diseases which are residue borne will survive in the soil
only a long as the residue (leaves, stems, fruit) for that crop
survives. In general, the length of the rotation for residue
borne diseases are shorter than the rotations required to
manage soil borne diseases.
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Wide host range.YesNoVerticillium
wilt
Includes buckeye rot and
root rotNoNo
Phytopthora
diseases
CommentsResistance
Maybe
seed
borneDisease
NoNoWhite mold(timber rot)
Wide host range. Causal
agent survives manyyears in soil.
YesNoRoot knot
3 races existYesYesFusariumwilt
NoNoFusarium
crown rot
Soil borne tomato diseases-rotations of
more than 4 years and fall tillage critical
The organisms that cause soil borne diseases may survive
long periods of time in the soil without any host. In most
vegetable systems, long rotations will keep soil pathogens
from rapid increases in populations. However, rotations
alone will not successfully manage soil borne diseases.
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Virus diseasesPowderymildew
Plectosporiumblight
Phytophthora blightFusariumfruit rot
Downy mildewBacterial fruit spotBlack rot
Pumpkin Diseases
Pumpkin diseases have very different characteristics and
thus need to be managed differently.
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Also affects squashNoYesBacterial
fruit spot
CommentsResistance
Maybe
seed
borneDisease
Readily windbornePartialNoPowdery
mildew
NoNo
Plecto-
sporium
blight
aka, gummy stemblight
NoYesBlack rot
Residue borne pumpkin diseases-rotations of
2-4 years and fall tillage critical
Rotations of 2 to 4 years will help to manage these
diseases of pumpkin.
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CommentsResistance
Maybe
Seed
BorneDisease
Water management
critical. Avoid
rotations withsolanaceous crops.
NoNoPhytophthorablight
NoYesFusarium
fruit rot
Soil borne pumpkin diseases-rotations of
more than 4 years and fall tillage critical
Long rotations are needed to avoid building up populations
of these soil borne pathogens of pumpkins.
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CommentsResistance
Maybe
seed
borneDisease
Overwinters in SE USor on weed hosts
NoNoVirusdiseases
Overwinters in SE USNoNoDowny
mildew
Pumpkin diseases that are neither
soil or residue borne
The organisms which cause these diseases do not survive
in the soil or residue.
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Post Planting Disease ManagementPost Planting Disease Management
••Fungicides/bactericidesFungicides/bactericides
••Apply materials preventativelyApply materials preventatively
••Importance of the latent periodImportance of the latent period
Latent period-Latent period-
the time between infection and symptom productionthe time between infection and symptom production. .
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Septoria Septoria leaf spot of tomato-latent period about 6 days.leaf spot of tomato-latent period about 6 days.
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Downy mildew of pumpkin-latent period 4-12 days.Downy mildew of pumpkin-latent period 4-12 days.
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1. The latent period means that there are normally1. The latent period means that there are normally
more infections present than the eye can see. more infections present than the eye can see.
2. Even the best fungicide/bactericide2. Even the best fungicide/bactericide
merely merely slows the production of slows the production of symptoms. symptoms.
3. Therefore, it is best to apply a pesticide in a 3. Therefore, it is best to apply a pesticide in a
preventative manner. preventative manner.
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High Disease
Low Disease
Hypothetical Fungicide Trial
Most fungicides will not completely control a disease.
Historically, those conventional fungicides which have had
success result in from 1/10 to 1/3 s much disease as
untreated crops.
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Biofungicides on snap beans 1
A=allowed, R=restricted, x=not listed
170
32R, ATrilogy + Kaligreen
77
140R, R, A, xOxidate + Trilogy + Kaligreen + Cohere
60
102AContans
43A, R, xBallad + Champion + Biotune
80
91A, xBallad + Biotune
% controlOMRI*Product
White Mold
*Organic Materials Review Institute
This information is based on published reports from 2006. The two
numbers for each organic treatment represent two different trails.
Note that sometime the trials differed greatly in the end result. If a
treatment is listed as controlling over 100% compared with the
control, the disease in this treatment was worse than the control.
Many organically labeled compounds require precise knowledge of
the characteristics of the compound.
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Biofungicides on snap beans 2
A=allowed, R=restricted, x=not listed
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106R, ATrilogy + Kaligreen
69
62R, R, A, xOxidate + Trilogy + Kaligreen + Cohere
160
49AContans
78A, R, xBallad + Champion + Biotune
0
65A, xBallad + Biotune
% controlOMRIProduct
Gray Mold
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Why scout?
Identify disease problems during the season
•To change practices this year
•For next year
Scout for diseases
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How to scout:How to scout:
Scout your crops on a regular basis (calendar). Scouting
supplies include a hand lens (10X or higher), paper for
notes, self sealing bags for samples, a marker pen, field
guide and possibly a digital camera.
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A=Healthy leaf; B=infectious pattern;
C=non-infectious pattern (nutrition?);
D=non-infectious pattern (stress?)
These diagrams illustrate some generalizations in
determining an infectious disease problem from a
nutritional or stress induced problem. Note that infectious
foliar diseases often produce a random distribution of
lesions on the leaf.
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Old leaf Old leaf chlorosis-muskmelonchlorosis-muskmelon
An example of a non-infectious problem. In this case, no
corrective action is required.
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Interveinal chlorosis-muskmelonInterveinal chlorosis-muskmelon
These muskmelon leaves probably suffer from a nutritional
problem.
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Alternaria Alternaria leaf blightleaf blight of muskmelonof muskmelon
A lesion caused by an infectious disease often results in a
lesion with an internal pattern such as the ridges that can
be observed here. Note that the ridges in this lesion are
concentric and resemble a ‘bulls-eye’. Such a pattern is
characteristic of diseases caused by the fungus Alternaria.
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Septoria Septoria leaf spot-tomatoleaf spot-tomato
Note the internal pattern present in these lesions caused
by Septoria. The margin of the lesions are a chocolate
brown and the center is gray. Note also the random
pattern of lesions on the leaves.
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Septoria Septoria leaf spot-tomatoleaf spot-tomato
A close up of these same lesions. Note that there are
small dark spots in the center of these lesions. These are
the structures of the fungus that causes Septoria leaf spot
and can bee seen with a hand lens.
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Contact herbicide damage-watermelonContact herbicide damage-watermelon
The random pattern of the lesions on this leaf could be
mistaken for an infectious disease. However, the lesions
observed here have little internal pattern. This is typical of
a lesion caused by a substance that kills the tissue on
contact, but does not cause the lesion to expand over time.
This leaf damage was caused by a contact herbicide.
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Contact herbicide damage-watermelonContact herbicide damage-watermelon
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Downy mildew-pumpkinDowny mildew-pumpkin
These chlorotic (yellow) lesions are limited by the leaf
veins, therefore the lesions are angular in appearance.
Note that some of the lesions are necrotic (brown).
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Downy mildew-pumpkinDowny mildew-pumpkin
This pumpkin leaf has been infected by the fungus that causes
downy mildew. The fungus can be seen growing on the leaf in the
areas circled in red, causing rectangular ‘fuzzy’ looking areas. The
downy mildew fungus can often be observed on a leaf when wet with
dew as in this photo. The observation of the downy mildew fungus
on the leaf is diagnostic, that is, can be considered proof of the
identity of the disease.28
Downy mildew-pumpkinDowny mildew-pumpkin
The margins of these pumpkin leaves are necrotic, causing
the leaf to assume a ‘burnt’ appearance. These symptoms
were caused by downy mildew of pumpkin.
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Powdery mildew of pumpkinPowdery mildew of pumpkin
The fungus that causes powdery mildew assumes a
talcum-like appearance. Although many different plants
are affected by powdery mildew, the fungi are specialized
to a particular family of plants. For example, powdery
mildew of pumpkin can affect other cucurbits, but cannot
affect tomato.30
Pumpkin virusPumpkin virus
This leaf is representative of the mosaic symptoms that can
occur as a result of virus infection. Papaya ringspot,
watermelon mosaic virus and zucchini mosaic virus are all
potyviruses, infect cucurbits and may result in symptoms
such those shown here.
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Pumpkin virusPumpkin virus
Leaf strapping is another symptom sometimes observed in
virus infections. The leaves shown here are infected by
one of the potyviruses discussed in the previous slide.
More than one virus may be present in the infection.
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Pumpkin virusPumpkin virus
Fruit may also have symptoms of virus infection such the
mottling seen above. Aphids are responsible for vectoring
potyviruses in pumpkins.
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Fusarium Fusarium wilt-watermelonwilt-watermelon
The wilting observed here can be distinguished from the
wilt of a plant that lacks water from the one-sided nature of
the symptom. This is typical of a vascular wilt disease.
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Fusarium Fusarium wilt-watermelonwilt-watermelon
Vascular discolorationVascular discoloration
HealthyHealthy rootsroots
In this photo, the reason why the plant in the previous slide
had a one-sided wilt can be seen. The vascular tissue in
half o this stem is discolored and non-functional. The roots
of plants affected by a vascular disease will look healthy.
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DiseasedDiseased rootsroots
Diseased roots will look discolored and rotten. Such roots
may result in a wilted plant, but not in the one-sided wilt
observed previously.
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Using a DiagnosticUsing a Diagnostic LabLab
1.1. CollectCollect fresh, donfresh, don’’t send over weekend.t send over weekend.
2.2. Send several examplesSend several examples
3.3. Crush proof containerCrush proof container
4.4. Provide lots of informationProvide lots of information
5.5. DonDon’’t pullt pull plants-do bag rootsplants-do bag roots
6.6. Press leavesPress leaves
7.7. Contact labContact lab