Pathogen Information and Management

Transcription

1 Pathogen Information and Management K.A. Cochran Assistant Professor & Extension Specialist Texas A&M University AgriLife Extension Dept. Plant Pathology & Microbiology

2 What is plant disease? A disruption of a plant that interferes with normal structure, function, or growth caused by a pathogen (or other factors) leading to development of symptoms. Baudoin, 2007

3 Basic disease cycle Overwinter: (plant or vector), debris, soil Pathogen reproduces & spreads Some pathogens have a secondary cycle within a single season Plant host & Favorable conditions available Pathogen causes disease symptoms in plant Infection Pathogen gains entry & overcomes plant defenses

4 Disease Symptoms & Signs

5 What are Symptoms vs. Signs? Symptoms-changes in plant growth or appearance in response to a pathogen Yellowing Wilting Necrosis Stunting Galls, witches brooming Sign- direct evidence of the pathogen, such as actual pathogen tissue Fungal tissue, sporulation Bacterial ooze

6 Sign vs. Symptom Symptom: Chlorosis, necrosis, wilting Sign: Acervuli (sporulation of fungi)

7 Plant Pathogens & Disease Examples

8 Bacteria Single celled organisms Prokaryotes Everywhere in environment Only some are pathogenic to plants Some pathogenic to humans can survive on plants E. Coli, Listeria sp., others Most that cause disease in plants won t make humans sick

9 MN Dept Ag ohioline.osu.edu UMN Ext. LSU PLPA Blog

10 Viruses Sub-microscopic Many are spread by vectors (insects) Some by mechanical means, seed Yellowing, loss of vigor, death of plant in some cases Best control is vector control, clean practices pnwhandbooks.org Peanut leaf TSWV

11 Nematodes Microscopic worms Infect plants and feed on nutrients Most are root feeders Sandy or clay soil, different species

12 Fungi Basidiomycetes Mushrooms Conks Puffballs Fairy rings Wikipedia.org ag.umass.edu

13 Fungi Ascomycete-cup fungi Imperfect too Most plant pathogens, but many important ecosystem members www4.uwsp.edu c1.staticflickr.com

14 Fungal Structures Recognize fungi and better understand how it lives & spreads Mycelium, hyphae: Vegetative growth, threadlike structures. Somatic tissue the body of fungus.

15 webstercountyschools.org

16 Fungal Reproductive Structures Phomopsis pycnidia Acervuli of Colletotrichum Phomopsis pycnidia in stem commons.wikimedia.org

17 Fungal Spores & Structures Ascospores Basidiospores Perithecia with asci lifeandscience.org Wikipedia.org

18 Fungal Spores & Structures- Conidia (clones!) Conidia are asexual spores, and come in large variety of shapes & sizes usyd.edu.au thegordonlab.net Cliffnotes.com

19 Other reproductive and survival structures Sclerotia- tough fungal tissue propagules in plant material/soil lasting years Rhizoctonia solani, others

20 Fungus-like microbes Oomycete-water molds Downy Mildew Root rots Pythium, Phytopthora Rutgers.edu livegpath.cals.cornell.edu

21 Oomycete Vs. true fungi dispersal Active & passive Passive webstercountyschools.org Apsnet.org This Photo by Unknown Author is licensed under CC BY NC ND

22 Disease Management

23 Basic disease cycle, the triangle, and management Opportunities for management at every phase! Host Pathogen reproduces & spreads Overwinter: (plant or vector), debris, soil Plant host & Favorable conditions available Environment Pathogen Pathogen causes disease symptoms in plant Infection Pathogen gains entry & overcomes plant defenses

24 Management Strategies Resistant or immune plants Avoidance via cultivation techniques Prevention Exclusion Protection Eradication Therapy Treatment

25 Resistance & Immunity Employing genetics and traits of the plant to naturally resist pathogens Direct Tolerance vs. Resistance Tolerance=plant can do well in spite of pathogen colonizing some tissues Resistance= plant prevents disease from occurring on genetic level Indirect Plant traits such as waxy cuticle can prevent pathogens from gaining entry

26 Avoidance Avoid disease development by making environment unfavorable for the pathogen with cultivation techniques Adjusting irrigation method and timing, use of mulch, tillage Different planting sites Different planting times Using adapted varieties

27 Slide by K. Ong

28 Slide by K. Ong

29 Slide by K. Ong

30 Slide by K. Ong

31 What is Integrated Pest Management? Using multiple disease control approaches to prevent and manage plant diseases Focus on prevention by creating an unfavorable scenario for disease development Multifaceted Focus on Prevention Effective, evidence based Ecologically responsible

32 Example of Implementing IPM Try to prevent disease- Maintain cultural practices (watering, pruning, etc) that make the environment unfavorable for disease and promotes healthy vigorous plant growth. Know your host Know what it needs, Stressed plants=disease more likely Drip irrigation to reduce leaf wetness period, prevent & reduce disease Sanitation: physically remove inoculum sources, tillage Debris, alternate hosts Clean all tools, shoes well. Bleach (1:10) soak tools in tub, dry Use least toxic chemical option if needed Use resistant/ immune selections to prevent disease again