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Plant Disease Management Uses an Integrated Approach • Exclusion • Plant resistance • Cultural controls • Chemicals • Microbiologicals University of Florida - IFAS 1 Integrated Plant Disease Management Exclusion • Regulation of plant material at ports, city, county, state or country boundaries – federal and state rules • Pathogen-free seed or plants • Seed certification • Meristem culture • Cuttings from clean “mother” plant under sterile conditions University of Florida - IFAS 2 Integrated Plant Disease Management Exclusion Don’t Pack a Pest http://www.dontpackapest.com https://www.youtube.com/watch?feature=player_embedded&v=x0S99cwnDqM University of Florida - IFAS 3 Integrated Plant Disease Management Exclusion Where did all the impatiens go? Downy Mildew caused by Plasmopara obducens on Impatiens walleriana https://edis.ifas.ufl.edu/pp309 University of Florida - IFAS 4 Integrated Plant Disease Management Plant Resistance Genetic • Immunity is the rule in the plant kingdom • If immunity does not exist, plant breeders develop cultivars with resistance to specific pathogens • Constitutive and inducible defenses Chemically or Biologically Induced • Application of chemicals or biologicals to induce production of defense compounds Adaptation • Plant adaptation to site University of Florida - IFAS 5 Integrated Plant Disease Management Plant Resistance Genetic • Graft susceptible top onto resistant root stock •http://content.ces.ncsu.edu/grafting-for-disease-resistance-in-heirloom-tomatoes •http://edis.ifas.ufl.edu/ep339: For Florida, roses grafted on 'Fortuniana' rootstock thrive University of Florida - IFAS 6 Integrated Plant Disease Management Plant Resistance Genetic • Constitutive: continuous defenses; includes cell walls, waxy epidermal cuticles, bark, leaf hairs – physical and chemical barriers • Inducible: defenses (chemicals or proteins) produced in response to invading pathogens; includes toxic chemicals, pathogen-degrading enzymes, deliberate plant cell suicide http://www.apsnet.org/edcenter/intropp/topics/Pages/OverviewOfPlantDiseases.aspx University of Florida - IFAS 7 Integrated Plant Disease Management Plant Resistance Genetic Systemic Acquired Resistance (SAR) • Activated when pathogen infects tissue • Long-lasting systemic immunity, even in tissues not infected • Relatively broad spectrum • Usually associated with increase in phytohormone salicylic acid (SA) University of Florida - IFAS 8 Integrated Plant Disease Management Plant Resistance Chemically Induced Systemic Acquired Resistance (SAR) • Use of SA or SA analogs can induce SAR-like responses • Provides resistance in plant tissues beyond application site (systemic) • Often referred to as “plant activators” • Benzothiadiazoles (ex: Actigard) used for plant protection http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4306307/pdf/fpls-05-00804.pdf University of Florida - IFAS 9 Integrated Plant Disease Management Plant Resistance Biologically Induced Systemic Acquired Resistance SAR) • Weak viruses Induced Systemic Resistance (ISR) • Triggered by non-pathogenic plant growth promoting rhizobacteria • Involves jasmonic acid and ethylene, rather than salicylic acid doi: 10.1105/tpc.113.111658. Plant Cell May 2013 vol. 25, no. 5, pp. 1489–1505 doi: 10.1128/AEM.71.9.4951-4959. Appl. Environ. Microbiol. Sept. 2005 vol. 71, no. 9, pp. 4951-4959 University of Florida - IFAS 10 Integrated Plant Disease Management Plant Resistance Adaptation “Right Plant for the Right Site” • • • • • • temperate vs. tropical; cold induction dry vs. rainy soil type: sand vs. clay day length others? Genetic resistance can be overcome if site is not right for the plant species University of Florida - IFAS 11 Integrated Plant Disease Management Cultural Controls • Crop rotation • Alternate host eradication – for pathogens and vectors • Sanitation of tools, equipment, potting containers, shoes, etc. • Improved plant environment, especially water management, air circulation • Nutrient management • Soil treatment, such as solarization, tillage • Mulches or other barriers University of Florida - IFAS 12 Integrated Plant Disease Management Chemical Controls Fungicides Bactericides Nematicides Insecticides Fumigants • • • • Seed treatments Soil treatments Root drenches Disinfecting tools • • • • Foliar sprays Trunk injections Trunk sprays Post-harvest use For fungicides and bactericides, the “cides” is not accurate. Most suppress rather than kill. There are no chemicals to use against plant viruses. University of Florida - IFAS 13 Integrated Plant Disease Management Chemical Controls Figure 1. U.S. Crop Protection Fungicide Use From: http://www.apsnet.org/publications/apsnetfeatures/Pages/Fungicides.aspx Also see: http://www.apsnet.org/edcenter/intropp/topics/Pages/Fungicides.aspx University of Florida - IFAS 14 Integrated Plant Disease Management Chemical Controls Year Fungicide Primary Use 1637 Brine (Salt) Cereal seed treatment 1755 Arsenic Cereal seed treatment 1760 Copper sulfate Cereal seed treatment 1824 Sulfur (dust) Powdery mildew and other pathogens 1833 Lime sulfur Broad spectrum foliar pathogens 1885 Bordeaux mixture Broad spectrum foliar pathogens 1891 Mercury chloride Turf fungicide 1900 CuOCl2 Especially Phytophthora infestans 1914 Phenylmercury chloride Cereal seed treatment 1932 Cu2O Seed and broad spectrum foliar diseases 1934 Dithiocarbamates patented Broad spectrum protectants 1940 Chloranil, Dichlone Broad spectrum seed treatment From: http://www.apsnet.org/publications/apsnetfeatures/Pages/Fungicides.aspx (IN)Organic Fungicides: https://www.extension.purdue.edu/extmedia/bp/bp-69-w.pdf Organic Materials Review Institute: http://www.omri.org/ University of Florida - IFAS 15 Integrated Plant Disease Management Chemical Controls Mode of action of some major fungicides classes, their FRAC code and resistance risk FRAC Code 1 Resistance Mode of action / inhibition risk Beta-tubulin assembly in mitosis (cytoskeleton and motor proteins) high Chemical Class Benzimidazoles 2 Dicarboximides MAP/Histidine-kinase in osmotic signal transduction medium-high 3 Azoles, Pyrimidines C-14 demethylation in sterol biosynthesis in membranes medium 4 5 7 9 Phenylamides Morpholines Carboxamides Anilinopyrimidine RNA polymerase I (nucleic acid synthesis) ^8 and ^7 isomerase and ^14 reductase in sterol biosynthesis Succinic acid oxidation (respiration) Methionine biosynthesis (amino acid and protein synthesis) high low-medium medium medium 11 Strobilurins Mitochondrial synthesis in cytochrome bc1 (respiration) high 16 Various chemistry Melanin biosynthesis (two sites) in cell wall medium 40 Carboxylic acid amides Cellulose synthase (cell wall formation in Oomycetes) low-medium M1 M3 Inorganics Dithiocarbamates Multisite contact Multisite contact low low M5 Phthalimides Multisite contact low Fungicide Resistance Action Committee: http://www.frac.info; http://edis.ifas.ufl.edu/pi131 University of Florida - IFAS 16 Integrated Plant Disease Management Chemical Controls From: University of Florida - IFAS 17 Integrated Plant Disease Management Microbiological Controls Fungi: Trichoderma, Candida, Muscodor, Pythium, Ulocladium, Verticillium Bacteria: Bacillus group, Streptomyces, Xanthomonas, Pseudomonas, Pantoea, Pasteuria, Agrobacterium, Paecilomyces, Burkholdaria http://www.apsnet.org/edcenter/advanced/topics/Pages/BiologicalControl.aspx https://www.epa.gov/pesticides/biopesticides University of Florida - IFAS 18 Integrated Plant Disease Management Microbiological Controls Effective because they produce: • Antibiotics • Lytic enzymes • Biocidal volatiles • Detoxification enzymes • Iron-chelating siderophores Effective because they outcompete the pathogens University of Florida - IFAS 19 Integrated Plant Disease Management Microbiological Controls Bacillus subtilis strains: •QST 713 •MBI 600 •GB03 •FZB24 Registered by EPA as biopesticide University of Florida - IFAS 20 Plant Disease Management Uses an Integrated Approach • Exclusion • Plant resistance • Cultural controls • Chemicals • Microbiologicals University of Florida - IFAS 21 Integrated Plant Disease Management GMOs Is there a place for GMOs in our integrated plant disease management tool box? University of Florida - IFAS 22 Integrated Plant Disease Management GMOs Some diseases cannot be controlled with any currently available methods! Florida Example: Bacterial Spot Disease of Tomatoes The Good, the Bad, and the Ugly: What the Future Could Hold for Bs2 Tomatoes http://edis.ifas.ufl.edu/hs1259 University of Florida - IFAS 23