Chile Pepper vs Soilborne Pathogens: Can the plant
Chile Pepper vs Soilborne Pathogens: Can the plant win? Michael Matheron Extension Plant Pathologist & Professor Yuma Agricultural Center [email protected] Known diseases of pepper Cause Number Bacteria
4 Fungi and Oomycetes 14 Viruses 17 Nematodes
10 Parasitic seed plant 1 Postharvest 4 TOTAL 50
From Compendium of Pepper Diseases Phytophthora blight Verticillium wilt Rhizoctonia root rot Phytophthora blight Verticillium wilt Rhizoctonia root rot All caused by soilborne pathogens Adapted to live and survive in soil Invisible to the naked eye
Questions related to disease What is the problem ? What is the cure ? Questions related to plant diseases
What is the problem ? What can I do to prevent or manage the problem ? To effectively manage a plant disease, we need to know what affects its development Requirements for disease development
First described in 1922 in New Mexico Phytophthora means plant destroyer (Greek) Phytophthora blight of pepper Symptoms Images courtesy of D. Lindsey Phytophthora blight of pepper Symptoms Oomycetes initially described as fungi,
but over time, significant differences compared to true fungi became apparent Characteristic Oomycetes True fungi Primary cell wall component Cellulose Chitin Vegetative nuclear state
Diploid Haploid Asexual spores with flagella Yes No Several biochemical differences as well, such as Reaction to specific fungicides
Disease cycle for Phytophthora blight Ristaino & Johnston. Plant Disease 83:1080-1089 Management considerations for Phytophthora blight of pepper The host Host resistance or tolerance to Phytophthora capsici is a desired goal Management considerations for Phytophthora blight of pepper
The pathogen Inoculum avoidance Use plants and transplants free of the pathogen Inoculum survival Crop rotation to nonhost plants Solarization of soil Some organic amendments can affect survival of Phytophthora in soil Management considerations for Phytophthora blight of pepper The pathogen
Deployment of fungicides Phytophthora disease management Protectant fungicides Protectant Fungicide Introduction 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 tin compounds (fentin acetate or fentin
Multisite contact activity Management considerations for Phytophthora blight of pepper The environment Soil and atmospheric water Since Phytophthora is a water mold, water management is critical Proper placement and duration of irrigation Enhance movement of water through soil Provide adequate field drainage in areas subject to high levels of rainfall
Management considerations for Phytophthora blight of pepper The environment Predisposition of plants to disease Drought stress Waterlogged soil Soil salinity Verticillium wilt of pepper Pathogens: Verticillium dahliae Verticillium albo-atrum
Verticil: A circular arrangement, as of or leaves, about a point on an axis. A whorl. flowers 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.
Courtesy of Berlanger and Powelson Verticillium wilt of pepper: Symptoms Images courtesy of D. Lindsey Disease cycle for Verticillium wilt Courtesy of Berlanger and Powelson Verticillium microsclerotia forming on dying plant tissue
Courtesy of Berlanger and Powelson Verticillium wilt of pepper Preplant management options Plant resistant or tolerant varieties if available Crop rotation to nonhost plants Verticillium has large host range (> 200 plant species) Microsclerotia can persist in soil for several years Certain crops (broccoli) can significantly reduce microsclerotia population in soil
Chemical soil fumigation Effective but expensive Application restrictions, loss of some products Soil solarization Verticillium wilt of pepper Management options in growing season Apply optimal rates of nitrogen & phosphorus Effective on some plant species Avoid overwatering On young plants of some species, overwatering
increases infection and subsequent disease severity Verticillium wilt of pepper Management after harvest Propane flaming Destroy Verticillium microsclerotia in crop residue Peppermint field Rhizoctonia root rot of pepper Pathogen: Rhizoctonia solani Origin of the name Rhizoctonia
rhiza (Greek for root) ktonos (Greek for murder) Rhizoctonia root rot of pepper: Symptoms Courtesy of G. Holmes Courtesy of P. Bosland Rhizoctonia solani Disease cycle for Rhizoctonia diseases
From Agrios, et al. Rhizoctonia root rot of pepper Management options Plant resistant or tolerant varieties if available Use fungicide treated seed Rhizoctonia solani has a very large host range Avoid saturated soil Avoid planting in soil having large amounts of undecomposed plant residue Could enhance growth and survival of Rhizoctonia
solani in soils Chile Pepper vs Soilborne Pathogens: Can the plant win? There is no silver bullet Develop and deploy an Integrated Disease Management Plan incorporating all tools that will contribute to reducing disease development to the maximum possible extent
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