Pathogens Can the plant win Michael Matheron Extension Plant Pathologist amp Professor Yuma Agricultural Center matheronagarizonaedu Cause Number Bacteria 4 Fungi and Oomycetes ID: 717821
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Slide1
Chile Pepper vs Soilborne Pathogens:Can the plant win?
Michael MatheronExtension Plant Pathologist & ProfessorYuma Agricultural Centermatheron@ag.arizona.eduSlide2
CauseNumberBacteria4Fungi
and Oomycetes14Viruses17Nematodes10Parasitic seed plant1Postharvest4
TOTAL
50
Known diseases of pepper
From Compendium of Pepper DiseasesSlide3
Phytophthora blight
Verticillium wiltRhizoctonia root rotSlide4
Phytophthora blightVerticillium wiltRhizoctonia root rot
All caused by soilborne pathogensAdapted to live and survive in soilInvisible to the naked eye Slide5
Questions related to diseaseWhat is the problem ?What is the cure ?Slide6
Questions related to plant diseasesWhat is the problem ?What can I do to prevent
or manage the problem ?Slide7
To effectively manage a plant disease, we need to know what affects its developmentSlide8
Diseaseseverity
Favorable environmentSusceptibleHostplantVirulent pathogen
Requirements for disease
developmentSlide9
Phytophthora blight of pepper Pathogen: Phytophthora capsici
First described in 1922 in New Mexico Phytophthora means ‘plant destroyer’ (Greek)Slide10
Phytophthora blight of pepperSymptoms
Images courtesy of D. LindseySlide11
Phytophthora
blight of pepperSymptoms Slide12
Oomycetes initially described as fungi, but over time, significant differences compared to true fungi became apparent
CharacteristicOomycetesTrue fungiPrimary cell wall componentCelluloseChitinVegetative nuclear state
Diploid
HaploidAsexual spores with flagella
YesNoSeveral
biochemical differences as well, such as
Reaction to specific fungicidesSlide13Slide14Slide15
Ristaino & Johnston. Plant Disease 83:1080-1089
Disease cycle for Phytophthora blightSlide16
Management considerations for Phytophthora
blight of pepperThe hostHost resistance or tolerance to Phytophthora capsici is a desired goal Slide17
Management considerations for Phytophthora blight of pepper
The pathogenInoculum avoidanceUse plants and transplants free of the pathogenInoculum survivalCrop rotation to nonhost plantsSolarization of soil Some organic amendments can affect survival of Phytophthora in soilSlide18
Management considerations for Phytophthora blight of pepper
The pathogenDeployment of fungicidesSlide19
Phytophthora disease managementProtectant fungicides
Protectant FungicideIntroduction date
Copper sulfate + lime (Bordeaux mixture)
1885
Cuprous oxide and other copper salts
1932
Dithiocarbamates
(
Zineb
,
Maneb
,
Mancozeb
, 1951-1962)
1931-1962
Phthalimides
(
captan
,
captafol
,
folpet
)
1949-1965
Triphenyl
t
in compounds (
fentin
acetate or
fentin
hydroxide)
1954
Chlorothalonil
1963Slide20
Phytophthora disease managementSystemic fungicides
Systemic FungicideIntroduction dateIsoxazoles (hymexazol
)
1974
Cyanoacetamide Oximes (cymoxanil,
Curzate
)
1976
Phenylamides
(metalaxyl, mefenoxam, Ridomil)
1977
Phosphonates
(fosetyl-Al, Aliette; phosphorous acid salts)
1977
Carbamates
(propamocarb, Previcur)
1978
Dimethomorph (Acrobat, Forum)
1988
Dinitroanilines
(fluazinam, Omega)
1992
Strobilurines
(azoxystrobin,
kresoxim
-methyl)
1992
Zoxamide
2004Slide21
Fungicides active against Phytophthora
Target siteCommon nameTrade name
FRAC
Code
Nucleic acid synthesisMefenoxamRidomil Gold
4
Mitosis
& cell division
Zoxamide
Gavel
22
Ethaboxam
22
Fluopicolide
Presidio
43
Respiration
Strobilurines
Cabrio
, Flint,
Quadris
11
Famoxadone
Component of
Tanos
11
Fenamidone
Reason
11
Cyazofamid
Ranman
21
Fluazinam
Omega
29
Ametoctradin
Component of
Zampro
45
Cell wall biosynthesis
Dimethomorph
Forum
40
Mandipropamid
Revus
40Slide22
Fungicides active against Phytophthora
Target siteCommon nameTrade name
FRAC
CodeLipid
synthesis and membrane integrityPropamocarbPrevicur
28
Unknown mode of action
Cymoxanil
Curzate
27
Fosetyl
-Al
Aliette
33
Phosphorus acid
&
salts
Phostrol
, etc.
33
Oxathiapiprolin
Orondis
U 15
Multisite contact activity
Copper salts
Kocide
, etc.
M 1
Mancozeb
Manzate
,
Dithane
M 3
Chlorothalonil
Bravo
M 5Slide23
Management considerations for Phytophthora blight of pepper
The environmentSoil and atmospheric waterSince Phytophthora is a “water mold”, water management is criticalProper placement and duration of irrigationEnhance movement of water through soilProvide adequate field drainage in areas subject to high levels of rainfallSlide24
Management considerations for Phytophthora blight of pepper
The environmentPredisposition of plants to diseaseDrought stressWaterlogged soilSoil salinitySlide25
Verticillium wilt of pepper Pathogens: Verticillium dahliae
Verticillium albo-atrum Verticil: A circular arrangement, as of flowers or leaves, about a point on
an
axis. A whorl.Slide26
Verticillium wilt of pepper Pathogens: Verticillium dahliae
Verticillium albo-atrum Verticil: A circular arrangement, as of flowers or leaves, about a point on an axis
. A whorl.
C
ourtesy of
Berlanger
and
PowelsonSlide27
Images courtesy of D. Lindsey
Verticillium wilt of pepper: SymptomsSlide28
Disease cycle for Verticillium wilt
Courtesy of Berlanger and PowelsonSlide29
Verticillium microsclerotia
forming on dying plant tissue Courtesy of Berlanger and PowelsonSlide30
Verticillium wilt of pepperPreplant management options
Plant resistant or tolerant varieties if availableCrop rotation to nonhost plantsVerticillium has large host range (> 200 plant species)Microsclerotia can persist in soil for several yearsCertain crops (broccoli) can significantly reduce microsclerotia population in soilChemical soil fumigationEffective but expensiveApplication restrictions, loss of some products
Soil
solarizationSlide31
Verticillium wilt of pepperManagement options in growing seasonApply optimal rates of nitrogen & phosphorus
Effective on some plant speciesAvoid overwateringOn young plants of some species, overwatering increases infection and subsequent disease severitySlide32
Verticillium wilt of pepperManagement after harvestPropane flaming
Destroy Verticillium microsclerotia in crop residue
Peppermint fieldSlide33
Rhizoctonia root rot of pepper Pathogen: Rhizoctonia
solani Origin of the name ‘Rhizoctonia” rhiza (Greek for ‘root’)
ktonos
(Greek for ‘murder’) Slide34
Courtesy of G. Holmes Courtesy of P. Bosland
Rhizoctonia root rot of pepper: SymptomsSlide35
Rhizoctonia solani Slide36
Disease cycle for Rhizoctonia diseases
From Agrios, et al. Slide37
Rhizoctonia root rot of pepperManagement options
Plant resistant or tolerant varieties if availableUse fungicide treated seedRhizoctonia solani has a very large host range Avoid saturated soil Avoid planting in soil having large amounts of undecomposed plant residueCould enhance growth and survival of Rhizoctonia
solani in soilsSlide38
Chile Pepper vs Soilborne Pathogens:Can the plant win?
There is no silver bulletDevelop and deploy an Integrated Disease Management Plan incorporating all tools that will contribute to reducing disease development to the maximum possible extentSlide39Slide40Slide41Slide42